Webster&Bennett DH Boring mills

BORING MILL OPERATION for the OPERATOR AND WORKS MANAGER WEBSTER BENNETT SERIES DH BORING MILLS TABLE OF CONTENTS Illustration of tire boring dogs and clamps. Illustration of hand-operated radius boring Title page. attachment. Table of Contents. Machining of locomotive piston rings. Radius turning: Introduction. Illustration of piston ring equipment. Illustration of radius turning attachment. Illustration of Series DH Boring Mill. Machining of locomotive axle boxes and equip- Pulley crowning. ment. Illustration of Series DH Boring Mill, Illustration of pulley crowning attachment. 31 Illustration of axle box equipment. 51 Preliminary attention and lubrication. Illustration of hydraulic chuck and controls. General operating instructions. 56 Tool layout, vacuum brake piston. Taper generating attachment. General operating instructions continued, 58 Tool layout, machining bull gear. Illustration of spur gear type taper generating Equipment. attachment, Tool layout, machining flywheels, operation 1. 16 Equipment continued. Illustration of control for taper generating Tool layout, machining flywheels, operation 2. Illustration of standard tool equipment. attachment. Tool layout, machining flywheels, operation 3. Illustration of standard and special chuck jaws. Beam type profile turning, Tool layout, electric motor stator frames. Boring mill practice. Beam type profile turning continued. Tool layout, variable pitch air screw hub. Boring mill practice continued. Line drawing of copy beam. Illustration of typical work stops. Boring mill practice continued, Illustration of special beam arrangement as Table of cutting rates. Machining of aluminum and aluminum alloys. fitted to larger mills. Capacity chart standard mills. Machining flywheels, pulleys and other components. Tool layout showing machining of pistons using profiling equipment. Capacity chart standard mills. Machining methods continued. Tool layout showing machining of piston crown Capacity chart--standard mills. using profiling equipment. Illustration of equipment for machining thin Adjustments to machine. rings. Illustration of standard types of hydraulically loaded profiling tool holder. Conversion tables. Illustration of equipment and tool layout for boring railway tires. Radius boring. Index. INTRODUCTION This handbook is supplied with the primary purpose of assisting On Webster Bennett machines, the generously proportioned the operator to obtain good results from the boring and turning slides and the extremely efficient turret enables the use of multi- mill. tool setups which will show a considerable saving in production time on components where the batch quantities will justify the It does not deal with the installation and maintenance of a machine expense of special tooling. except to the extent of comparatively simple adjustments that may In this handbook, we have stressed the importance of providing be carried out by the operator. the machine with adequate lubrication, but in addition to this, the mill should be kept clean and in a properly adjusted condition. Installation and general maintenance work for our boring and turning mills is fully dealt with in our Maintenance Manual. The operator who works on a piecework basis will find that a few minutes' daily attention to his boring mill will pay dividends. The small-size modern boring and turning mill with a single A machine that is correctly lubricated, adjusted and where the slides and operating mechanism are kept clean will inevitably produce turret has very rapidly achieved a position where it is considered more accurate work with greater ease than a mill that has not an essential production machine tool. It possesses certain inherent qualities which result in ease of operation, ease of loading work, received this attention. great rigidity which enables the best use to be made of cemented For example, it is recommended that all exposed slides are carbide tools together with retention of the original accuracy of the cleaned down at least once daily and then wiped over with a rag machine due in part to the fact that the slides are not exposed to charged with clean lubricating oil. This practice will prolong the the abrasive action of swarf as is the case with a chucking lathe. initial accuracy of the machine. SERIES DH VERTICAL BORING AND TURNING MILL PRESSURE GAUGES CLUTCH AND BRAKE RAPID POWER TRAVERSE AND FEED DIRECTION CONTROL D CONTROL SPEED CONTROL OIL LEVEL INDICATOR SERIES DH BORING AND TURNING MILL PRELIMINARY ATTENTION AND LUBRICATION CLEANING All traces of protective grease should be carefully cleaned from circulating through the whole system; this is most important. the machine using paraffin or kerosene. Particular attention should It is important to note that the chuck must not be rotated backwards be paid to the slides, to the feed screw, the vertical feed shaft and by hand, or damage to the feed box may result. See later notes on to the splined shaft at the back of the saddle. controls. The oil gun should be applied to all oil points shown on diagram A full description of the lubrication arrangement of the machine pages 10 and 11. follows since this will enable the operator to appreciate the necessity All slides and feed shafts should be hand oiled, and the mill should for the very small amount of attention that is required to keep the be run at low speeds for, say, half an hour to ensure that oil is machine in first-class order. LUBRICATION The lubrication of Series DH Boring Mills is practically fully auto- The main base of the machine forms the oil sump, and the filler matic since all bearings and gears are pressure-fed from a bypass for this is on the operating side of the machine. Lubrication to the system off the main hydraulic circuit. The oil pump feeding the power main spindle is by means of oil to the upper bearings and thrust track and lubricating circuits is fitted in the clutch box of the machine. The and by grease to the lower ball bearing. No visual oil level is pro- smaller of the two pressure gauges which are fitted to the arm vided, but oil is pressure-fed through the thrust tracks, and so long carrying the control panel registers the lubricating oil pressure as the oil gauge is registering a copious supply of oil flows through which should be approximately ten pounds per square inch when the thrust bearing and the upper races.

The machine has attained its normal working temperature. Box is splash lubricated and the oil level in this box is maintained by Vacuum Light. Inhibitor treated. A feed pipe from the lubricating circuit. The rapid power traverse and feed reverse box is pressurized. The following quantities of oil will be required: and oil from this box is returned to the main sump after feeding the various bearings and gears. Slides and those slide bearings which are not fitted with either 60 DH self-oiling bushes or arranged for oil gun lubrication are lubricated. The oil for lubrication and servo hydraulic use is drawn from the syphon feed reservoirs. The oil level in these reservoirs is maintained by small pipes connected to the pump and filling is end of the pipe being fitted with a fine strainer. It is essential that controlled by means of a tap on the side of the column of the machine, this strainer should be kept clean as the clogging of it will result in a gauge provided on one of the boxes giving the level. Do not immediate loss of oil pressure, which loss will be registered on the overfill or excess oil will fall onto the chuck. larger of the two gauges. It is most important to ensure that the correct lubricating oil is Access to the filter is through the oil filter box on the side of the used for hydraulically-operated machines, since these mills will not machine. It is necessary to remove the coarse strainer basket and function properly with the wrong grade of oil. insert a hand and wipe off any foreign matter adhering to the filter. The filter must be cleaned frequently for the first month following Velvus Three Lubricating Oil, which is marketed by the British installation of the machine and afterwards once a week should be Oil and Turpentine Corporation, should be used, since this oil has adequate. Should there be any drop in the pressure of the hydraulic been subjected to protracted tests and is the most suitable type. circuit this filter should be inspected at once and checked for clogging. Should it be necessary to use alternative brands of lubricating oil when Velvus Three is unobtainable or when it is desired to restrict Machines supplied in the United Kingdom are charged with oil stocks to a relatively small number of brands, these alternative oils before leaving our works, although it is sometimes necessary to may be used. replenish oil lost in transit due to faulty slinging. GENERAL OPERATING INSTRUCTIONS All Series DH Boring Mills are designed to provide servo hydraulic air of cylinders. No adjustment is required to the brake since it will control for main clutch, speeds, feeds, reversal of feed, rapid power continue to function until the linings have worn and require replace- traverse and braking. ment. As previously mentioned, the pump for providing hydraulic In the BRAKE OFF position of the lever the chuck may be pressure is fitted in the clutch box of the machine and is accessible rotated by hand, since the brake is disconnected and the clutch by taking off the lid of this box. The pump is a Varley gear type disengaged. It is important to note, however, that the table should and a separate relief valve situated in the machine column is provided not be turned backwards, even by hand, since this practice will which will serve to maintain reasonable control of oil pressure. This inevitably result in damage to the free wheel in the feed box. On pressure is indicated on the larger of the two pressure gauges in the left-hand machines this need not apply as the table is reversible and control arm bracket. The main driving clutch and the clutch operating should it be necessary on any occasion to turn this by hand the reverse the rapid power traverse are both operated hydraulically. It should lever should be set in neutral when the horizontal driving shaft and be noted that with the exception of these clutches the use of hydraulic the feed box will be disengaged from the table drive. This does not pressure is confined to the actual movement of gears and dog apply to left-hand machines without reverse. clutches, the drive to the table being through a twelve-speed gear- To rotate the chuck by hand it is desirable to set the speed box box, transmission bevels and helical gear and pinion. The feeds of gears for maximum table speed and on 48 and 60 machines it may the machine are provided by a twelve-rate gearbox, which incor- be essential to use a capstan bar in one of the chuck tee slots. Stop porates a freewheel: changes are by dog clutches which are the driving motor to avoid the necessity for holding the clutch lever in engaged or disengaged by servo hydraulic arrangement. BRAKE OFF position. The hydraulic control provides a very easy, direct means of selecting speed and feed rates. Two small dials calibrated with The second lever on the panel controls the feed direction and the spindle speeds in revolutions per minute and feed rates in inches or rapid power traverse. Selection of feed reverse and feed engage- millimeters per revolution are mounted on the control panel. These ment is by toothed clutches and the rapid power traverse positions dials are attached to controllers which rotate on ball bearings. The should be engaged slowly to avoid clashing these. speed change is interlocked with the clutch both mechanically and Rapid movement of this control lever from the rapid power hydraulically in order to ensure that the gears cannot be changed traverse position to the feed position will result in the breakage whilst the clutch is engaged or conversely that the clutch is not of the shear pin which connects the feed box coupling to the feed engaged with the gears out of position. supply shaft. This breakage is caused by engaging a stationary The rates of feed may be selected whilst the machine is running clutch with one which is rotating rapidly and the resultant shock is by setting the dial to the feed rate required. sufficient to shear the pin. The lever should therefore be moved from the extreme position at either right or left to midways towards Although this is permissible, changing the feed with the machine the feed position. running on high spindle speeds may result in some damage to the feed box clutches. It is, therefore, undesirable to change feed on Selection of vertical or horizontal traverse in conjunction with the the coarser range with the chuck running at speed. A warning plate feed or rapid power traverse direction obtained by the hydraulic on the machine stresses this point and a safety peg is fitted to prevent control lever is given by the two positions of the feed selection lever the operator changing directly from top to bottom feed. mounted on the cross slide end bracket. This lever controls an arm carrying a spiral pinion which meshes in one or other of the spiral Two other levers are provided on the control panel and their gears attached to the cross slide feed shaft and screw. The feed functions are clearly indicated. See page 13. should always be disengaged by placing this lever in its neutral The clutch lever, as previously mentioned, is interlocked with the position: instantaneous disengagement is obtained by tapping the speed change dial. This lever has three working positions: OFF, STOP, and START. When the lever is set to START, The turret is operated by two levers, one of these unbinds the it should be moved fairly slowly, since provision is made for operating turret door through the first part of its upward movement and withdraws the clutch in two stages. During the first portion of the lever movement oil pressure is reduced in order to provide a gradual starting motion to the chuck, which is desirable when the speed box gears are set for high speeds. 

When the final position of the lever is on 30 machines, one revolution of the rotating lever moves the reached full pressure is applied. At slow to moderate spindle turret to its next indexing position: on 48 and 60 mills, two revolutions are required.

The correct way to index the turret is as follows:

Push the turret binder lever upwards to the top of its slot. Use the right hand for this and at the same time keep the left hand on the turret revolving lever. Rotate the turret in either direction until the tool box or boring bar required is, say, 15 from the vertical and then allow the binder lever to drop halfway in its slot. Continue to rotate the turret until the plunger snaps home, then push the binder lever down to its lowest position.

CONTROL PANEL AND PRESSURE GAUGES GENERAL OPERATING INSTRUCTIONS continued

In general, all gears and clutches in the speed box, feed box, rapid power traverse, and feed reverse box are moved by means of dual-diameter pistons working in cylinders, one end of the piston being subjected to constant pressure of oil, while the other end of the piston which is of larger diameter, has pressure applied to it or oil exhausted from it by the action of the controller valve on the control panel. In certain cases, the pistons are stationary, while the cylinders move the gear shift clutches. Those gear changes on the speed and feed boxes which require a triple gear to be set in an intermediate position employ an additional piston and cylinder, which piston has a limited stroke and overrides the power of the end position pistons.

To index the turret bores exactly central with the spindle for limited stroke and overrides the power of the end position pistons, reaming and drilling operations, the saddle is moved towards the center of the table until a small scraped surface at the bottom side of the saddle coincides with the side of a notch cut in the cross slide. The surfaces are set by feel and will be found to provide an accurate and simple location.

In left-hand machines, it will be found more convenient to use the left hand for operating the binder lever and the right hand for the turret rotating lever. Make a habit of using this method and always have one hand on the rotating lever before withdrawing the plunger. Neglect of this precaution may cause injury if an unbalanced turret with heavy boring bars in it is allowed to rotate unchecked.

Each gear clutch cylinder carries a small interlock rod, which is a piston valve for the interlocking device, and these cut off the supply of high-pressure oil to a small valve, which in turn prevents the clutch engaging unless the gears are correctly meshed. A device applied to the first shaft of the speed box consists of cast iron friction discs held together by oil pressure, which firstly serve to prevent rotation of the shaft caused by the tendency of the disengaged plates to spin due to oil drag and secondly provide an automatic clutch which engages the rocking arrangement to the shaft.

The turret slide locking lever, when moved upwards, binds the vertical slide. It should always be employed when taking heavy facing cuts, but its use is unnecessary for finish facing.

The saddle locking lever need only be locked for the maximum turning cuts possible with the machine and should not be used for finish or boring.

In left-hand machines, excepting those with special low or high-speed drive, the table is arranged to reverse, and a lever is provided at the side of the machine, below the table, for this purpose. The table should be rotating slowly when operating this lever. Damage will be caused if the table is reversed at higher speeds, and the lever should pause in neutral until the table stops before engaging reverse direction.

Handwheels on Series DH Boring Mills controlling the movement of saddle and turret slide are provided with adjustable micrometer dials. These dials are graduated in divisions on those machines with English calibration. The graduations on machines with metric calibration represent 0.05 mm for each division. The clutch lever may be left in the Start position since as soon as the gear change is effected, the machine will start.

OIL PRESSURE Report to the foreman if the hydraulic pressure drops below 180 lbs. per square inch. If cleaning the filter has no effect in raising the pressure.

STANDARD EQUIPMENT The basic equipment supplied, while on 48 and 60 mills, one B2X set of Morse taper sockets, type P, extended tool holder is included. For general purpose work, the following equipment should be considered essential:

Additional B2 or B2X tool holders.

Cemented carbide tools T X inclusive: One set for cast iron, brass, malleable iron, phosphor bronze, etc., and one set for steel or aluminum work ADDITIONAL EQUIPMENT When precision finish bores are required, David Brown reamers semi-finish boring prior to using the David Brown reamer for sizing. should be used for sizing these, and special collets are provided. Alternatively, a combined double-ended cutter and reamer bar will for holding these reamers type R. be suitable, this bar carries a Kelly-type floating reamer and has Where fairly large batches of components are to be machined, the advantage that one pass only will be required for semi-finish the double-ended cutter boring bar, type Q, should be used for boring and reaming. CHUCK JAWS AND CHUCK EQUIPMENT One set of standard chuck jaws is supplied with every machine. These chuck jaws are precision ground in sets and may be used. It is possible, in an emergency, to fit cast iron blocks as parallels for locating previously machined surfaces of work at below the standard jaws, these blocks being tenoned to fit the second setting. chuck slipper at the bottom and grooved to accommodate the jaw Special jaws taller than the standard ones may be supplied in tenon on the top surface. CHUCK JAWS AND CHUCK EQUIPMENT continued A complete set of studs, dia. for 48 and 60 and dia. for Sets of soft steel jaws may be used for second setting components 36 machines should be included in the general equipment for although the mill is normally provided with a four-jaw independent holding work. An adequate supply of table nuts is also necessary. chuck. These jaws should be machined in position to the diameter of the work to be gripped. Sets of special stops similar to those shown on page 64 should be available. These can readily be made from round steel bar. Alternatively, copper clamps may be used for fitting over the drilled and tapped and provided with tommy bar holes. The plain serrations of the hard jaws in order to avoid bruising of finished stops are primarily for locating finished faces at second setting. diameters. The adjustable type is very useful for supporting and adjusting the height of workpieces at first setting. The other type of stop, The bore of all chucks fitted to Series D Mills is 6 diameter used where the table slots are not suitably spaced, are useful pieces and is concentric with the spindle. This bore should be used for of equipment. spigoting any fixtures that are required. Special spring stops should be used for supporting frail components or parts where it is essential to avoid distortion, such as aluminium pieces and fabricated steel jobs, etc. The construction These chucks are usually of three-jaw type, although four-jaw and of these spring-loaded stops will be quite clear from the drawing five-jaw combination chucks have been supplied. and in use, the small knurled locking screw is slacked back and the spring-loaded plunger allowed to position itself against the When using concentric chucks, work should be trued up and surface of the component that requires support. The locking screw checked using the independent jaws, tightened using the concentric is then tightened onto the taper face of the plunger. locking mechanism, and the component should be rechecked for true running. Any small inaccuracy should be rectified by adjusting the This type of spring-loaded stop will give adequate support to independent jaw screws, after which the concentric action of the thin castings without any possibility of distortion, but it is important chuck can be used for the complete batch of work. On these chucks, to use light springs. it is advisable to use soft jaws for second setting machining when Many workpieces will require to be retained by using a center previously machined diameters are to be gripped. When these bolt clamp, and all boring mills are provided with a 4 dia. tapped jaws are skimmed in position, it is essential that they should be hole in the center of the spindle for this purpose. gripped onto a circular plate or ring to ensure that all backlash is taken out of the centering mechanism. All machines have hollow spindles, and the cap which is tapped out whit. for the center bolt is usually removed when boring Plain self-centering chucks are also supplied, and notes given operations are carried out to allow swarf to pass through the spindle. above regarding machining of soft jaws are applicable to these This cap is retained by four screws, also. GENERAL BORING MILL PRACTICE The method of operating the machine has been described in work can be produced since it will be found in most cases that some detail together with the lubrication arrangement, but the one roughing cut and one finishing cut only will be required. following notes and instructions will be a useful guide for dealing with general turning work. We appreciate that some of these For finishing large faces and diameters with face widths of recommendations and instructions are of an elementary nature and more than, say, 2 on cast iron work, a broad cutting tool should be the skilled boring mill operator will be conversant with them. used. Before the advent of cemented carbide, this method of finishing It is always essential to ensure that castings or forgings are held was almost universal, but it appears to be less used nowadays. It as firmly and as rigidly as possible since the heavy cuts that can does provide a very rapid means of finishing with carbide, and be taken will exert considerable pressure on the workpiece. 250 feed should be used in conjunction with a flat tool approximately Elementary precautions to be observed are that castings and wide. The cutting edge of this tool should not be absolutely forgings should not be gripped on tapering diameters with parallel flat but should be lapped off towards the sides. jaws unless some additional means of support is available, or if Each rule and the micrometer dials on the handwheels are gripped in this manner, care should be taken to avoid using heavy provided with five colored tabs, and for batch work, full use should feeds. be made of these for sizing. Colored inserts in each turret face The gripping of many components can be assisted by judicious correspond to these. clamping, but this clamping should always be immediately over It should be noted that the vertical feed mechanism is not stops which aid vertical location. In general, it should be considered designed to withstand the very heavy stresses imposed upon it by bad practice to clamp any component at all when it cannot be drilling large diameter holes from solid in steel. Where such work supported immediately below the clamp. is necessary, an initial hole should be put through first using a drill A further point regarding the gripping of workpieces with jaws from diameter. A fine feed must be used for this, and it is that if the job is gripped on the outside diameter and becomes is desirable to use coolant. heated during machining, the strength of the jaw grip will increase. Most castings will be cored out for the necessary bores and for On the other hand, when a component, for example, a large ring rough boring, a single-point boring bar should be used. The rough is gripped inside with jaws, the heating up will cause the job to boring of small cored holes may be handled by using three-point slacken, and if a considerable amount of heavy work is to be carried core drills. If the core is running out badly, it is often desirable out, it is essential to retighten the chuck jaws to avoid the job moving. to bore the top of the hole for about 1 deep to the size of the core drill in order to give this support. A special short boring bar may be used for this purpose. It will be obvious, of course, that any work which tends to distort due to jaw pressure should be roughed out using the jaws tightly For small batches of work, single-point boring bars can be used gripped but slacked off as far as possible, consistent with safety for finish boring since the mill will produce round, parallel bores when finishing. within very narrow limits. For batch work, however, this method of sizing will be uneconomical, and floating reamers should be used Most jobs can be set on three fixed stops to give vertical location. for finishing. In certain cases, it may be desirable to use two fixed stops and two adjustable stops which are better than four adjustable ones, since A previous section dealing with standard equipment refers a more or less constant height of the position of the casting or to the reamers and bars that are available. Broadly speaking, the forging relative to the table will be maintained. fastest method of boring will be to use a single-point boring bar for roughing, taking two cuts, double-ended cutter bar for semi- One of the major advantages of the boring mill for machining is finishing using a fairly coarse feed, say, per revolution that roughing cuts may be taken to within 0.15-0.20 of finished size followed by a David Brown floating reamer cutting at approximately without fear of a cut running in and so scrapping the job. This 25 feet per minute with 0.83/1.25 feed. This note applies to cast factor is a very important one when considering the rate at which iron or bronze work. 

GENERAL BORING MILL PRACTICE continued

It is important that the cutting speed of the David Brown reamer be carried out on the modern boring and turning mill, but an should be kept fairly low, since otherwise rapid wear will take place endeavor has been made to cover representative classes of work on the blades with a consequent deterioration of finish. 006 008 and to provide general information that is likely to be useful to should be left in the bores for reaming. An alternative arrangement operators, excepting those on highly specialized work. will be to use the combined cutter bar and reamer previously As an introduction, it should be stated that the Series DH range described. This reamer is a different type. Feeds should be similar, of mills is very solidly constructed and by virtue of the fact that all but leave 031 in the bore from the single-point tool to allow a coarse feed to be employed for the double-ended cutter. the power used in driving the rotating units of the machine is very The David Brown reamer has the very considerable advantage low. that it may be adjusted to measurement obtained with a micrometer Due in part to this and to the fact that driving gears, shafts, and across the edges of the blades. This adjustment is carried out by clutches are generously designed metal can be removed at very rotating the small adjusting plate with the special key provided. fast rates. This plate is calibrated to facilitate setting and a similar plate on fast rates. the other side of the reamer should be locked when the correct On standard machines 15 motors are provided with 36 setting is obtained. mills and 20 or 25 motors according to the class of work Smaller size David Brown reamers have knurled micrometer for the 48 or 60 mills. Overloads on the motors may be set to the collars for direct adjustment. highest practicable figure and the power available can be used to Constant use of these reamers on cast iron or other dusty work the full. may cause stiffening of the floating blades due to the ingress of dust. Nowadays the use of cemented carbide tools is universal and The dismantling of the reamer blades is only a matter of seconds there will be few jobs upon which they cannot be employed. and they should be taken down and cleaned whenever there is a Certain steel castings, for example, those of the 10-12 per cent. tendency to stiffness. Failure to observe this precaution may result manganese group, certain of the stainless steels and steel castings in the production of oversize bores. of low quality where there is a considerable amount of blowholes, For taper boring and turning, the turret slide may be swiveled sandy inclusions and hard spots, may prove suitable subjects for to approximately 40 on either side of the vertical plane. To swivel machining with high-speed steel tools, particularly for rough this slide, the taper peg at the back of the saddle must be removed, operations. Cast iron, malleable iron, aluminum, bronze alloys, the four bolts on the same facing taken out, and the two bolts from steel forgings, and most grades of steel castings should always be the lugs at the bottom of the swivel slide. Four nuts at the front of machined using cemented carbide tools. the swivel slide are then slackened and the slide swiveled by Since the development of negative rake technique with steel applying the chuck key to the square end of the worm shaft at the grades of cemented carbide, many jobs that were originally con- top of this slide. When work entails heavy cutting, the four bolts sidered unsuitable for machining with these tools are now quite at the rear of the saddle should be replaced and tightened. satisfactory subjects. Additional tapped holes for them are exposed as the swivel slide is set over. It is most difficult to give an accurate table of cutting speeds The swivel slide is graduated in degrees, and the micrometer and feeds since the amount of negative rake and the shape of the collar mounted on the worm shaft is calibrated with divisions tool when machining steel will have a very considerable bearing representing 10 minutes. on the metal removal rate. The table given herewith should, therefore, be taken as a general guide and not adopted as a standard. When the swivel slide has to be reset for parallel boring and turning, the taper peg should be lightly tapped into position before With reference to the machining of cast iron, it is not considered the bolts are tightened, ensuring at the same time that the alignment that negative rake on carbide tools is necessary in any way. of the small scraped index faces at the bottom of the swivel slide Generally speaking, the 3 top rake will be found quite suitable for and saddle is correct. This setting is most important and should be all cast iron and cast iron alloys. Tools with 7-10 top rake should very carefully rechecked after the bolts have been tightened. generally be used for machining malleable iron castings while It will obviously be impracticable to attempt to describe even aluminum cutting should be carried out using tools with the broadly the method of machining the full range of work that can maximum possible top rake. GENERAL BORING MILL PRACTICE continued For machining steel, as previously mentioned, negative rake cutting edge of the tool. A trickle of coolant or an intermittent cutting is most desirable. In the first place, the use of a negative splash will inevitably result in cracking of the cemented carbide tip. rake tool usually results in short, easily controllable swarf, which is Another general rule that should always be observed is that the a most important point when work is being machined on a boring tool overhang should be as small as possible. A tool that projects mill. too far from the tool box will result in vibration and consequent rapid wear of the carbide tip. The amount of negative rake required for any given material can only be obtained by experiment, although in broad terms, the A further point to note is that when machining with cemented negative rake should be in the direction of the chip flow and may carbide on interrupted cuts either iron or steel or on the rough vary from 3 to 10 . surface of a forging or steel casting, it is desirable to arrange for the cutting depth to be distributed along the greatest possible When using cemented carbide tools or cutting steel, it is always length of tip in order to lessen the stress on the tool point. desirable to remove sharp cutting edge by means of a diamond For this reason, a tool with an inclined cutting edge should hand-lap since otherwise this edge will deteriorate rapidly, partly always be used. The type of tool recommended is that shown as due to the shock of cutting but mainly to abrasion of the fine edge with swarf. on page 17. There are one or two points regarding the grinding of cemented It is important to note that negative rake cutting, while it enables carbide tools that must be observed if the best use is to be made metal to be removed at a faster rate, entails the use of considerable of these. Firstly, the periphery of a wheel is not satisfactory for power. grinding since the carbide edge is undercut and weakened. It is important, of course, to use a correctly bonded wheel, and there It is, therefore, advisable to avoid overloading the motor driving is a large number of special grinding wheels on the market. It is the machine to the point where the motor may stall, causing tool believed that one of the best wheels is the Neven impregnated breakage. A few minutes spent in experimental cutting will deter- diamond type. connected in the driving motor circuit, and the calibrations of this This wheel may be used both for rough grinding and finish should be marked with a red line showing the maximum permissible grinding cemented carbide tools, but it is essential to use a copious current that may be used. supply of water. 

When machining steel, it is desirable to grind a chip breaker on tools. Tools should be ground with quite a light pressure; they should never be ground dry and cooled by dipping in water. The tools should always be rocked backwards and forwards across the surface of the grinding wheel, and the clearance and rakes carefully checked. It is also essential for the tip to be ground towards the cutting edge and not away from it.

We should recommend the operator to study one of the handbooks obtainable from the carbide tool manufacturers, which usually give full information on the depth of groove, distance from cutting edge, and shape of chip breakers. With reference to the grades of cemented carbide, most tool makers supply a number of grades and will advise on the most suitable of these for any material.

On machines fitted with a cutting coolant system, it is essential to ensure that a full flow of coolant is projected straight onto the tool. HIGH-SPEED STEEL TOOLS AND STELLITE

It will be appreciated that high-speed steel tools cover a very wide field of use in the boring and turning mill. The type of tool which consists of a high-speed steel end but welded on a carbon steel shank will be found very satisfactory. Stellite tools have certain advantages on some work and are frequently used for rough machining steel castings.

MACHINING OF ALUMINIUM ALLOYS

Nowadays, boring mills are employed to a very considerable extent in the machining of aluminium alloy castings of all kinds, particularly those used for either turbine or reciprocating aeroplane engines. Certain of these alloys present problems in machining, particularly those of the magnesium group where some fire risk is entailed.

Ordinary alloy castings should not present any difficulty at all in machining since the production of a good quality finish is a simple matter, providing that the right types of tools are used.

Generally speaking, it is desirable to use the grade of cemented carbide tool normally recommended for machining steel, particularly those primarily suited for very high-speed finishing cuts. Some engineers prefer the use of a cutting lubricant when machining aluminium alloys. There is no doubt that some cutting lubricants can be very satisfactory in use, and a lubricant based on heavy mineral or lard oil diluted with paraffin has been found to give good results.

In general, it should be considered essential to diamond lap all the finishing tools used for light alloys. When grinding tools, the top rake should be a compound angle that will direct the stream of swarf in a convenient direction away from the work.

Referring again to magnesium alloy fires, swarf should be cleared from around the boring mill at regular intervals to avoid a considerable amount of this being involved if a fire is started. In particular, swarf should not be allowed to lie around the back of the chuck since the fanning of this when revolving at high speeds will accelerate the spread of a fire.

When machining the magnesium alloys, certain elementary precautions must be observed if the fire risk is to be minimized. This material can be cut at a rate of 2,000 feet per minute or more, and at these speeds, it is essential that the tool is not allowed to rub either by disengaging the feed with the tool still in contact with the revolving work or by allowing any rubbing against the tool due to an unnecessarily large radius or insufficient side clearance.

When rough machining this material, it is considered desirable to use a fairly coarse feed, say, 0.21-0.42 inches per revolution since the heavy swarf that is produced will have no tendency to ignite. When finish machining, the feed will have to be selected to suit the quality of finish required, but it is desirable to use finishing tools with very sharp cutting edges, maximum top rake, and virtually a point with very little land on the cutting edge.

Water must on no account be used in an attempt to quench a magnesium swarf fire since this would cause the formation of hydrogen gas, which combined with atmospheric oxygen will produce a gaseous mixture that is easily ignited. Sand thrown on the molten magnesium will quell the fire very quickly, and there are a number of special powders that have been developed. One of these is a mixture of precipitated chalk and asbestos, and this should be used in preference to sand.

NOTES ON THE MACHINING OF FLYWHEELS, VEE GROOVE PULLEYS, AND OTHER COMPONENTS PARTICULARLY APPLICABLE TO BORING MILL WORK

An elementary job is the machining of a simple cast iron flywheel or pulley, and a detail of this operation is given for the benefit of the cutter. Machining should be carried out in the following manner:

First Setting:

Rough turn the outside diameter.

Rough face rim and boss.

Rough machine web if necessary.

Rough bore.

Slacken jaws to avoid distortion.

Finish bore and ream.

Finish machine outside diameter and faces.

Second Setting:

Reverse flywheel.

Rough machine faces and web.

Finish machine faces.

In other cases where the periphery is machined for vee belts, the grooves should be cut within a 0.15 size when rough machining and finish grooved after slackening the jaws and finish boring.

It should be noted in certain cases that it is desirable to rough and finish face the rim and boss on one side of the flywheel or pulley and reverse this, locating vertically from parallel stops mounted on the table, and the remainder of the machining carried out as previously described. This method does provide a much firmer location, particularly where it is possible to clamp. This method avoids the constant resetting and rechecking that occurs when attempting to set work simultaneously in two planes.

Feeds and speeds that should be used are as follows, these being based upon a machining allowance not exceeding a cut and finish machining on a cast iron approximately 180 Brinell:

Rough facing and turning: 200-250 ft. per min.

Finish facing and turning: 021-042 inches per revolution.

This is the minimum feed that needs to be employed since it is possible to commence feeding the vee groove form tool at 0.21 inches per revolution, changing down as the area of cut increases. There are, however, very many rings produced from steel that are provided on three of the vice clamp jaws. Castings or forgings which cannot be machined in the manner. These stops are spaced equidistantly and it should be noted described. Whenever it is possible for such rings to be turned from that on the other jaws no vertical location is provided. The pinching castings or forgings and parted off after machining, it is suggested screws on the three vice jaws are locked to the component and the that this method is fully explored by the designer of the component ends of the jaws are set to diametrical index lines on the faceplate. since in most cases this is the cheapest and most accurate way of These three jaws are then clamped to the faceplate by tightening producing thin rings. the nuts on the tee bolts. In those cases where it is essential to make the rings singly, a The next procedure is to tighten all the remaining pinching special attachment must be made for gripping and vice jaws clamp screws and to clamp the other nine jaws to the faceplate. It should generally as shown on page 25 must be used. be noted that the spring-loaded stops are free to move vertically In most cases where a quantity of rings is required, this justifies during these operations and the knurled locking screws on these a more elaborate setup, and it will be desirable to mount a faceplate may now be tightened when the stops will provide support. on to the chuck of the boring mill. This faceplate should have Some care is needed in setting the rings in this manner, but the 24 radial tee slots, 12 of which can carry the vice clamp jaws and time taken is quite short, and once the method of setting has been 12 the necessary spring-loaded support stops for supporting the mastered it is possible to set any ring in less than two minutes. work between the jaws. Such an arrangement is indicated on page Moderate feeds will have to be used when machining, particularly The type of vice jaw clamp recommended is shown, and the for steel rings. Work can be produced to very accurate limits small ring that is gripped in this clamp is a high tensile steel gear using the equipment described, and subsequent operations on the ring that was used for power-operated gun turrets on aircraft. rings should be dealt with either by locating these on an adaptor The method of locating and gripping work using the equipment plate fitting the previously machined diameters or by clamping described is to have 12 vice clamps loose on the faceplate surface from the outside to machine internal diameters and changing over and position the ring in these, locating vertically off the fixed stops the clamps to grip from the inside for completing external diameters. MACHINING OF RAILWAY TYRES A common work subject for boring and turning mills is the machining of tires, and a full-width grooving tool can be used for the production of high tensile tires for railway use. Such tires should ring groove. be gripped on the thread with taper jaws or, alternatively, held by There are two methods of machining the lip groove: one employs using special tire clamps similar to those shown on page 27. The a narrow grooving tool which produces a parallel vertical groove most common form of tire in this country has the Gibson type of and utilizes a further tool for cutting the taper. In the other case, fastening, and we give a brief outline of the machining procedure this groove can be cut using a full-size form tool, but more care together with approximate feeds and speeds that can be used. has to be used with the latter arrangement to avoid tool breakage. The setting of tires using taper jaws need not be described, Speeds will vary very considerably according to the hardness but if the special clamping arrangement is used, the tire should be of tires, but in general, speeds from 150-350 feet per minute should located on the vertical setting faces and checked for rock, as any be used for boring and facing and from 90-120 feet per minute for inaccuracy of the rim may preclude setting at all four points. lipping and grooving. Feed rates should be 0.15-0.31 inches per revolution for boring if one cut only is needed according to the It will, therefore, be necessary to rotate the tire on the setting quality of finish required, while the grooving tool can be fed in at surfaces until no rock is evident. Failure to observe this practice 0.05 inches per revolution, and the lipping tool should either be fed will result in the bore of the finished tire being oval due to by hand or 0.025 inches per revolution feed used. distortion caused by clamping. The tire should be set for true Coolant is essential for satisfactory use of the cemented carbide running by using the radial locating bolts, and when this is done, tools used, and a copious supply must be fed to the lipping and the clamps should be locked. grooving tools. Generally speaking, the machining allowance in the bore of Where it is essential to take roughing and finishing cuts in the railway tires is fairly small, approximately - - depth of cut is main bore, feeds up to 0.62 inches per revolution should be used common, and in many cases, it will be found possible to finish-bore for rough machining with negative rake tools. at one pass. It is desirable to face the step before boring in such Continental fastenings usually require a groove cut at an angle cases, and a separate tool should be used for this and for boring to the tire face. A hand-operated toolholder with an angled tool the step. slide may be supplied for machining these grooves and is indicated THE USE OF SPECIALIZED EQUIPMENT FOR RAILWAY SHOP WORK The use of boring and turning mills in railway shops has resulted The parting tools are staggered to ensure that the rings are cut in a demand for specialized equipment for certain work. One of off in sequence, and it is a simple matter for the operator to grip a the commonest jobs for which the smaller size boring mills are used ring lightly as soon as it is parted off and twist this quickly through is the production of piston rings, and we have developed the special the parting-off tools. equipment shown on page 29. In general, approximately 0.10 is left on the width of piston rings The illustration shows a piston ring pot being held to the chuck to allow for a subsequent grinding operation, but this practice is surface by taper jaws impinging on the taper flange of the casting. not invariable, and it is possible to produce rings that are parallel In many cases, this flange will not be available, and where clamping within very narrow limits straight from the parting-off operation lugs are not provided, it will be necessary to drill four equidistant without the necessity for additional operations. radial holes at the lower end of the pot for finger clamps. Some piston rings require to be radiused on the outside edges In every case, it is desirable to take a facing cut across the and it is essential in some cases to avoid any breakage of the inner bottom of the piston ring pot casting as a preliminary machining edges of the rings caused by the parting-off tools. It is then usual to operation. This facing is a matter of a few minutes' work only, and set the gang of parting-off tools to commence cutting simultaneously, results in the ability to hold the pot casting as rigidly as possible and so reduce vibration. The following speeds and feeds and method The parting tools are fed to a point where approximately 0.20 of operation may be taken as a general guide when using the piston of metal is left measured from the inside diameter. The rings are ring equipment. then radiused using a special tool holder with multi-radius tools and finally, the bank of rings is finished bored when each ring falls off Simultaneously rough bore and turn 120-200 ft. per min. immediately the boring cut is completed. It is, however, seldom necessary to alter the adjustment Rough bore to within 0.15 finish size including bore of the keep. since it is carefully set before leaving the works. Set box over to e in an end-wise direction to bring the keep towards the center of the chuck. One of the self-centering jaws is provided with an auxiliary slide Rough bore keep clearance. which is fitted with a scale and micrometer dial. The function of Reset box to original position and finish bore. the slide is to allow the horn cheek faces on an axle box to be Set box approximately 0.20 end-wise in the same direction as offset to any predetermined amount in relation to the center of the before and bore oil clearance. axle box bore. The adjustment provides a maximum offset of a Finish face boss. in either direction, Cut upper radius. Each self-centering jaw is provided with adjustable clamps that cut lower radius, can be arranged to suit any size of axle box. These clamps grip on the horn cheek flanges. Those boxes having parallel horn cheek It should be noted that levers are provided on the large jaws to flanges may be located from the inside of the upper flange on the enable these to be clamped firmly to the machine table when they facings at the top of the jaws, but it is sometimes necessary to use have been positioned and that it is usual to fit the keep to the axle the special parallel packing pieces that are provided for vertical box for machining bores and faces. location of axle boxes with tapering horn cheek flanges. Axle boxes Most locomotive boxes are made in bronze and have bronze of this type are mounted on the outside face and in those circum- inserts and white metal facings with cast iron keeps. The cutting stances it is usual for the axle box to be machined by planing to speed on rough facing and rough boring operations should, provide the correct location. therefore, be approximately 250 feet per minute using 0.031 and Two end stops are used for setting the correct position of the 0.042 inches per revolution feed. bore relative to the end of the axle box, on one of these a scale and For finishing, boring oil clearance and finish facing the mill pointer permits accurate measurement of the movement of the stop should be run at maximum speed and tools should be carefully and box. lapped to allow for a broad cut finish and 0.125 inches per revolution The turret equipment consists of three flanged boring bars, one feed should be used. It is easily possible to produce a mirror-like for rough boring, one for finish boring and the third for radiusing finish on white metal and bronze inserts and very accurate results the lower end of the bore. In addition, standard tool holders carry that require little or no hand scraping may be obtained without any facing and radiusing tools. difficulty. SPECIAL ATTACHMENTS A considerable number of attachments may be supplied with our timing collars correctly with the feed engagement clutch. boring and turning mills and a brief description of the majority of these together with operating instructions and general advice are At the end of the thread, the tool is retracted using the horizontal given in the following pages. feed handwheel, the rapid power traverse engaged by the rapid power traverse control, returning the tool to the commencement of the thread. The tool should then be advanced with the necessary SCREW CUTTING ATTACHMENT increment of cut and the feed engaged using the rapid power This attachment is generally as shown on page 33. It consists traverse feed engagement lever and matching the timing collars. of a small auxiliary gearbox fitted to the horizontal feed supply shaft It is imperative that the feed and rapid power traverse control which is provided with a lever that can be set in one of two positions, lever should not be moved to provide reversal of feed, or the feed one marked Feed and the other Thread. selection lever disengaged until the thread is completed. It is Change gears are provided which allow English pitches to be essential, of course, that the timing collars are correctly matched. The above notes apply to internal and external threading, but they are equally applicable to scroll cutting using the feed selection It is important to note that metric pitches cannot be cut with lever in the horizontal feed position. machines arranged for English threading since machines with a metric screw cutting attachment are invariably fitted with metric With reference to the type of tool that is recommended for screw screws and turret slide gearing to provide metric increments. cutting, the time taken to cut a thread is very considerably reduced by using a circular chasing tool. When using the screw cutting attachment, it is always desirable to ensure that the turret slide is slightly overbalanced and an A satisfactory thread cutting tool of similar type can be made additional balance weight or two should be fitted to ensure this. from a Herbert or Landis die mounted by brazing or clamping on The tables on page 34 give the range of threads that can be cut to a suitable shank. For fairly large threads, it is sometimes desirable and the change gears required. Access to the change gears is to adjust the position of the screw cutting tool vertically for side obtained by removal of the cover of the box and when mounting cutting in order that a first-class finish may be obtained. A suitable change wheels, 0.05-0.10 backlash should be allowed. tool holder has been developed for this application. Cemented Timing collars are provided at the top of the vertical feed supply carbide chasers are available. shaft, and one of these is attached to the shaft itself. The upper collar is geared to the feed engagement clutch, and when screw In addition to screw cutting, the screw cutting attachment may be cutting, it is essential that the collars are matched correctly before used for tapping in conjunction with a suitable tap holder, or commencing to cut the thread. alternatively, work can be threaded using a self-opening diehead. A simple attachment has been developed for use with the Herbert It is important to note that the feed dial is set to the correct feed diehead, which is shown on page 35. rate: this feed rate is always given on the instruction plate relating to the screw cutting box. Referring again to engagement of the feed and matching of the To cut a given thread, the procedure is to set the necessary indicator dials, if dials are a minute amount out of alignment, move change wheels, position the lever at Thread, set the feed box control the feed handwheel slightly forward to impart some backlash into to the correct feed rate, advance the tool to the work, engage the the train of gears and so ensure the feed engagement dog clutch vertical feed by means of the feed selection lever, and then engage going into full engagement. Recheck on timing dials. TABLE OF ENGLISH THREADS AND CHANGE WHEELS Threads NOTE: Machines supplied with screw cutting attachment for Metric threads have special feed screws, saddle worms, etc. Machines arranged for cutting English threads are unsuitable for Metric threading. Metric threading attachments are unsuitable for English pitches. TAPER GENERATING ATTACHMENT For producing tapers that are not obtainable by swiveling the A simple formula for obtaining the angle to which the swivel turret slide of the machine, or where it is undesirable in the interests slide should be set, for a taper not covered by gearing only, is given of efficient production to set the turret slide for taper boring or below. This applies to tapers from 0-40 measured from the turning and then reset for parallel work, taper generating attach- horizontal plane. Other tapers may be produced by swiveling the ments are supplied. turret slide only. The attachment couples, by means of suitable gearing, vertical and Let A = angle to be produced on work. horizontal feed shafts of the machine, and the ratio of the gearing B = the angle produced by the taper generating attach- gives the tangent of the angle required. A friction clutch is inter- ment with the turret head set vertically. posed in the gear train, and this clutch is operated hydraulically from V = the travel of the turret slide. a control valve conveniently fitted near to the main control panel of H = horizontal travel of saddle. the machine. The gearbox is fitted at the left-hand end of the cross O = the angle to which the swivel slide is to be set slide on right-hand machines, and the right-hand end of the cross outwards to correct B. slide on left-hand machines. Spur-type gears are used. The attach- ment will cover tapers ranging from 3-40 measured from either Then, vertical or horizontal planes, but it is usual to supply one set only of and sine X = sine A × V change gears to give a stated angle, although sets of gears may be supplied to order. Where, Cotangent B = . A general arrangement drawing of the box is shown on page 37 from which it will be noted that when the attachment is used for It will be apparent that the figures for X will have to be obtained producing tapers between 3-40 measured from the horizontal plane from the trigonometric tables. the hydraulic clutch is fitted on the feed screw of the machine. For tapers ranging from 3-40 measured from the vertical plane, the Alternatively, instead of using cotangent B to obtain X, the ratio clutch and driver are removed from the feed screw and fitted on to between the horizontal and vertical slide movements could be used. the feed shaft. Oil under pressure is supplied to the clutch by means Cotangent B is equal to the inversion of the ratio of the gears of of a flexible pipe, and the changeover of the clutch is a simple matter. the taper generating attachment. An idler gear is provided to enable the direction of the taper to be changed. Interlocks are included with the equipment which prevent the Select gear train from chart of angles higher than this  Selection of the incorrect power feed for the taper that is being when the gears will be: turned, these interlocks being hydraulically operated. 40 60 It should be noted when using the attachment, it is not possible to engage the rapid power traverse at the completion of the tapered 66 50 face without retracting the tool from the work, as in general, if the tool Then Sine is traversed straight back without relieving, the work will be scored due to backlash in the gears. It will be apparent that the attachment will produce tapers to a = 90 - 86 7 high degree of accuracy where these are stated in terms of the = 3053 tangent of the angle and it is nearly always possible with suitable gearing to provide for any taper within the For those unusual cases where a taper of less than 3 has to be range to a reasonable degree of accuracy. Where a taper is required produced, a worm gear type generating attachment may be supplied which cannot be obtained with sufficient accuracy by gearing, the but this will have a mechanically operated clutch and can only be swivel slide may be set over slightly to act as a compensator and in used to reverse the direction of taper by fitting opposite hand worm this way exact results may be obtained. or spiral gears. PROFILE TURNING ATTACHMENTS A simple form of profile turning attachment has been developed Tool layouts on pages 43 and 44 show typical profile copying to deal with the machining of contours on faces or diameters of work. components. The master profile cams require to be an exact replica of the profile required. These cams locate vertically on a ledge provided The attachment provides a convenient method of profile turning on the beam facing and are usually dowelled in position when they which avoids the necessity for subsequent resetting of the com- have been set correctly. ponent for this. The setting of a master cam on the beam is a simple matter when It consists of a beam, on which a master cam is mounted, that can sliding toolholders having vertical or horizontal movement are used, be set across the chuck surface, and a toolholder arranged to slide since the former need only be set to produce correct diametral and provided with a tracer to contact the cam used in conjunction dimensions and the latter, lengthwise dimensions. with either the vertical or horizontal power feed of the machine. Initial setting of the cams that are used with angular sliding tool The tracer is held in contact with the master cam by oil pressure holders is a more difficult matter and some experimental cutting will obtained by tapping the servo hydraulic power circuit of the machine. probably be necessary before the proper position is obtained. It will be evident with angled sliding tool holders that diametral The beam is arranged to swing and tip generally on the lines as dimensions and depths will be affected by displacement of the cams, shown on the photograph on page 42 which indicates an attachment but once the cam is correctly positioned and dowelled subsequent fitted to a BO machine. In its working position, the beam is locked machining will be simple provided that the distance between the across the chuck to a bracket on the right-hand side of the boring tool point and the tracer point is maintained as a constant dimension. mill but a later design which differs slightly from the photograph has vertical adjustment of both the pivoted end of the beam and of the This profile turning equipment may be fitted to machines already right-hand retaining bracket for this. This arrangement is clearly in service although in these cases special auxiliary brackets will be shown on the line drawing on page 41 and has the very considerable necessary for attaching the beam supports, and if older Series D advantage over earlier type attachments in that the height of the boring and turning mills of our manufacture require this profiling beam can be varied over a wide range to deal with differing heights equipment, pneumatically loaded tool holders are used instead of of components and moreover can, if necessary, be utilized as a the hydraulic ones previously referred to, the optimum air pressure means of providing increments of cut where a large number of being 80 lbs. per square inch. profiling cuts have to be taken due to heavy machining allowances. Four types of sliding tool holders may be provided dependent on the type of work that has to be profile turned. Sketches of these Datum faces are provided at each end of the beam for setting, are shown on page 45. with the use of a dial gauge mounted on the surface of the chuck, to ensure that the beam lies in a position parallel to the surface of the There are important points to observe regarding the profiling of chuck and it is necessary to make this check every time the height contours using either angled or vertical tool holders, firstly the tool of the beam is reset. The pivoted end is adjusted by means of a must be reground with very great precision to ensure that the radius handwheel and screw, but for the bracket at the right-hand side, of the tool is exactly similar to the radius of the tracer point and the adjustment is by simple rack and pinion, the pinion being also that the center of the tool radius is exactly on the center line provided with a square to suit the chuck key, of the tool. Page 39 PROFILE TURNING ATTACHMENTS continued In addition, the distance between the finishing tracer point and the machine for other profiles and a master cam will have to be the point of the tool is critical and the tool should always be set to provided for these. It should be noted that when using a vertical a gauge which usually measures from the end face of the tool holder sliding tool holder the maximum climb is 30 although the tool holder ram. will successfully machine a falling angle or contour at 60°, the angles given being measured from the horizontal plane. This latter measurement is particularly important on angled tool holders since any discrepancy of the tool in relation to the tracer A further point of importance when profile turning is that care point will result in a profile that varies very considerably in terms must be taken to avoid the tracer peg striking the tool holder casing of depth and diametral measurement from the correct one. at the end of its slot, due to faulty setting of the turret slide. It is essential that the maximum vertical movement required by the cam A pressure reducing valve and a pressure release valve are is covered by the movement of the tracer peg of the sliding tool included with hydraulically loaded profile copying equipment. These holder in its slot. valves are mounted on a small control box which is attached to the main control panel. The pressure reducing valve permits adjustment Failure to observe this will result in the beam being badly of operating pressure, whilst the other valve exhausts oil from the strained or broken. tool holder cylinder and allows the ram to be retracted. One application of the profile attachment is the production of tapers and a small flat plate, calibrated in degrees, may be supplied As will be apparent, tool holders having vertical displacement for fitting to the beam facing. The plate is arranged to swivel to will be used in conjunction with the horizontal power feed of the 30° for producing concave tapers or convex tapers, both measured machine, tool holders with their sliding rams at 45° may be used from the horizontal. See page 45. with either vertical or horizontal power feed whilst horizontally operating tool holders will be used in conjunction with the vertical Increments of cut may be made by lowering the complete beam power feed of the machine. in conjunction with a dial gauge mounted on the chuck to check the exact increase in depth of cut both ends of the beam require setting The depth of cut and the feed rate permissible will depend upon accurately or by taking out the tool from the tool holder and the shape of the profile being machined as well as the type of adjusting a setting screw at the back of the tool. material. In general, depths of cut from 0.03 to 0.05 should be made with a feed rate of, say, 0.015 per revolution on steel work and 0.021 to 0.031 A more usual arrangement is to provide a series of double-ended on cast iron, bronze or aluminum. tracers, these tracers being arranged to advance the tool by except for the final cut where approximately 0.010 only is left for One disadvantage of the arrangement for small quantity pro- finishing. duction is that a hardened profile cam has to be made for every type of profile that has to be produced and these cams are fairly SPECIAL ATTACHMENTS FOR RADIUS TURNING, ETC., FOR expensive to make. The advantages of the attachment are that as WHICH THE COPY BEAM ARRANGEMENT MAY BE USED mentioned previously, it is very simple in character, and it enables For certain special work the cam beam can be employed to the profiling work to be carried out at the same setting as the rest mount tool holders for producing radii and tapers. Special tool of the machining, since the beam is swung clear whilst the other holders are usually operated through suitable gears by means of a operations are being performed. For batch work the profile attach- driving peg held in a tool holder attached to the main turret, the ment will repeat contours to within very narrow limits once the cam horizontal power feed being used. In some cases a small electric has been accurately set. motor driving through an auxiliary gearbox provides a feed to Since it is customary to supply a profile attachment for a given the special tool holder and in other instances hydraulically fed component or series of components, the operator may have to set slides are used. STANDARD TYPES OF PNEUMATIC PROFILING TOOLHOLDER Page 45 RADIUS BORING ATTACHMENT An example of a hand-operated radius boring attachment is In addition to the rotating slide type of spherical boring attach shown on page 47. The pivot pin is bored to provide location for ment other attachments have been developed for producing hemi- a tool-setting gauge. The tool holder shown is arranged to produce spherical contours. One of these consists of a tool holder that can four sizes of spherical bores, the two smaller ones are obtained by be attached to the turret face of the machine and which is provided setting the tool to the gauges provided but the larger sizes necessi- with a slide giving a horizontal movement of the boring bar. This tate the fitting of an extension piece to the tool holder and a rubbing slide is attached to a link, the other end of which is held by a pin plate at the back of this extension piece to provide additional mounted in a bracket on the swivel slide of the machine. The support. Both these additions are shown mounted in position in distance between the two pivot pin holes of this link is equal to the the illustration. radius of the spherical contour that is to be produced and the attachment is used in conjunction with the vertical feed of the boring It will be apparent that it is essential for the pivot pin of the mill. rotating tool slide to be exactly on the centre line of the machine spindle if a true section of a sphere is to be produced. The saddle This attachment is rather limited in its application since it will of the boring mill must, therefore, be positioned in its central only produce spherical contours within 30 on either side of the position by means of the scraped location faces previously described. horizontal plane. RADIUS TURNING ATTACHMENT The radius turning attachment shown on page 49 is designed to operations and reset for finish turning. produce a limited range of spherical contours and an example of Measurement of the diameter of the sphere produced may be the type of component for which the attachment is used is the made with a micrometer caliper gauge. machining of spherical seating, self-aligning marine engine bearings. The position of the saddle of the mill must be set to ensure that It consists primarily of a radius arm mounted on the column of the the trunnion carrying the tool slide has sufficient clearance at each machine, the pivot for this arm being set on the exact centre line of the end of its guide. machine spindle. Provision is made for radial adjustment in relation to the tool holder slide by a plate attached to the radius arm and When the attachment is not in use the radius arm may be removed it will be noted that the axis of the tool is always maintained on a and any other machining operation required can be performed. line measured from the centre of the sphere that is being machined, It is thus unnecessary to make a separate setting of the component This arrangement is essential for the production of a truly accurate for the spherical turning operation. The support bracket. 

At the second setting, the rim is finish faced and the boss machined. A 36 boring mill is used for the operation, and a 25 Coventry and the inside of the rim is radiused. At the third setting, the piston is held concentric; a chuck is mounted on the existing chuck of the machine to facilitate holding the component. At the first setting, special taper jaws are used. The web, outside diameter, and face of the rim are rough and finish machined, and the bore is rough machined. At the second setting, the component is reversed and held in soft jaws, and the machining on the other side of the flywheel is completed. At the third setting, the flywheel is again gripped with soft jaws, the bore is sized and chamfered, the starting ring fitting diameter is finished, undercut and radiused, and the rim is again finish faced. The total floor-to-floor production time for this component is 40 minutes.

The tool layout for machining and locating medium-sized ship-sized propellers, as shown on page 52, is a very interesting boring mill application, and as will be seen from the drawing, three-blade propellers are automatically set in proper relation to their blades by means of the swiveling clamps provided. The tool arrangement for the electric motor stator frame shown on page 62 illustrates a duplex boring tool holder which we have standardized for this class of work since it produces ribbed frames. Faces on two opposite clamps are arranged for shimming below their base to ensure that all four blades are properly aligned.

The four-blade propeller is also held by similar clamps, but the standardization of the base is a ribbed frame. Faces on two opposite clamps are arranged for shimming below their base to ensure that all four blades are properly aligned.

The tool layout for machining the piston crown shown on page 56 indicates the application of the profile turning attachment previously described. A large bull gear, which is shown on page 58, is machined at four settings and is an excellent example of boring mill work. It will be noted that one of the eccentrics is machined while the gear is scaled from the main bore off a special eccentric fixture. For machining the eccentric, the tool should be set for simultaneous rough facing on both sides of the piston, turn 3/4 dia, and form radius inside rim, rough form 5/16 radius on bosses, and rough form 13/32 undercut 3/16 deep. The type of material to be machined, the depth of cut, the speed in ft/min, the feed in inches/rev, the top cutting material, the rake, and the lubricant should be considered for each type of tool.

It should be stressed that this table provides a general guide only for the cutting capacity of W. B. Mills and an indication of feeds, speeds, and tools that may be used. Most castings and forgings will have moderate machining allowances that do not necessitate very heavy cuts. Cuts shown may be taken without unduly stressing the machine. The best combination of speed and feed will be found by experiment; where the maximum given speed is used, the minimum depth of cut stated should be taken. Some figures apply only when 25 and 30 motors are fitted to the machine.

After a period of use, there will be a certain amount of backlash in the horizontal feed screw. This should be taken up by adjusting the locknuts on the saddle nut. These will be found on the left-hand side of the saddle on right-hand mills and on the right-hand side of the saddle on left-hand mills.

Wear on slides is taken up by the usual taper strips, and to retain the accuracy of the machine