Plan View showing Flywheel Casting Chucked for TurningFig. 3. Plan View showing Flywheel Casting Chucked for Turning
Plan View showing Flywheel Casting Chucked for Turning
Fig. 3. Plan View showing Flywheel Casting Chucked for Turning
Work that is to be turned or bored should first be set so that the part to be machined is about central with the table. For example, the rim of a flywheel should be set to run true so that it can be finished by removing about the same amount of metal around the entire rim; in other words, the rim should be set concentric with the table, as shown inFig. 3, and the sides of the rim should also be parallel to the table.
A simple tool that is very useful for testing the position of any cylindrical casting consists of a wooden shank into which is inserted a piece of wire, having one end bent. This tool is clamped in the toolpost and as the work revolves the wire is adjusted close to the cylindrical surface being tested. The movement of the work with relation to the stationary wire point will, of course, show whether or not the part runs true. The advantage of using a piece of wire for testing, instead of a rigid tool, is that the wire, owing to its flexibility, will simply be bent backward if it is moved too close to a surface which is considerably out of true. The upper surface of a casting can be tested for parallelism with the table by using this same wire gage, or by comparing the surface, as the table is revolved slowly, with a tool held in the toolpost. An ordinary surface gage is also used for this purpose. The proper surface to set true, in any case, depends upon the requirements. A plain cylindrical disk would be set so that the outside ran true and the top surface was parallel with the table. When setting a flywheel, if the inside of the rim is to remain rough, the casting should be set by this surface rather than by the outside, so that the rim, when finished, will be uniform inthickness.
As far as possible, chucks should be used for holding cylindrical parts, owing to their convenience. The jaws should be set against an interior cylindrical surface whenever this is feasible. To illustrate, the flywheel inFig. 3is gripped by the inside of the rim which permits the outside to be turned at this setting of the work. It is also advisable to set a flywheel casting in the chuck so that a spoke rests against one of the jaws as atd, if this is possible. This jaw will then act as a driver and prevent the casting from slipping or turning in the chuck jaws, owing to the tangential pressure of the turning tool. When a cut is being taken, the table and work rotate as shown by arrowa, and the thrust of the cut (taken by toolt) tends to move the wheel backward against the direction of rotation, as shown by arrowb. If one of the chuck jaws bears against one of the spokes, this movement is prevented. It is not always feasible to use a chuck jaw as a driver and then a special driver having the form of a small angle-plate or block is sometimes bolted directly to the table. Another method of driving is to set a brace between a spoke or projection on the work and a chuck jaw or strip attached to the table. Drivers are not only used when turning flywheels, but in connection with any large casting, especially when heavy cuts have to be taken. Of course, some castings are so shaped that drivers cannot be employed.
Turning Flat and Cylindrical SurfacesFig. 4. (A) Turning a Flat Surface.(B) Turning a Cylindrical Surface
Turning Flat and Cylindrical Surfaces
Fig. 4. (A) Turning a Flat Surface.(B) Turning a Cylindrical Surface
Turning in a Boring Mill.—The vertical type of boring mill is used more for turning cylindrical surfaces than for actual boring, although a large part of the work requires both turning and boring. We shall first consider, in a general way, how surfaces are turned and then refer to some boring operations. The diagramA,Fig. 4, illustrates how a horizontal surface would be turned. The tooltis clamped in tool-blockt1, in a vertical position, and it is fed horizontally as the table and work rotate. The tool is first adjusted by hand for the proper depth of cut and the automatic horizontal feed is then engaged. When a cylindrical surface is to be turned, the tool (provided astraight tool is used) is clamped in a horizontal position and is fed downward as indicated atB. The amount that the tool should feed per revolution of the work, depends upon the kind of material being turned, the diameter of the turned part and the depth of the cut.
Most of the parts machined in a vertical boring mill are made of cast iron and, ordinarily, at least one roughing and one finishing cut is taken. The number of roughing cuts required in any case depends, of course, upon the amount of metal to be removed. An ordinary roughing cut in soft cast iron might vary in depth from1/8or3/16inch to3/8or1/2inch and the tool would probably have a feed per revolution of from1/16to1/8inch, although deeper cuts and coarser feeds are sometimes taken. These figures are merely given to show, in a general way, what cuts and feeds are practicable. The tool used for roughing usually has a rounded end which leaves a ridged or rough surface. To obtain a smooth finish, broad flat tools are used. The flat cutting edge is set parallel to the tool's travel and a coarse feed is used in order to reduce the time required for taking the cut. The finishing feeds for cast iron vary from1/4to3/4inch on ordinary work. The different tools used on the vertical mill will be referred to more in detail later.
All medium and large sized vertical boring mills are equipped with two tool-heads and two tools are frequently used at thesame time, especially on large work.Fig. 9illustrates the use of two tools simultaneously. The casting shown is a flywheel, and the tool on the right side turns the upper side of the rim, while the tool on the left side turns the outside or cylindrical surface. As a boring mill table rotates in a counter-clockwise direction, the left-hand tool is reversed to bring the cutting edge at the rear. By turning two surfaces at once, the total time for machining the casting is, of course, greatly reduced. The turning of flywheels is a common vertical boring mill operation, and this work will be referred to in detail later on.
Tools for Boring and Reaming HolesFig. 5. Tools for Boring and Reaming Holes
Tools for Boring and Reaming Holes
Fig. 5. Tools for Boring and Reaming Holes
Boring Operations.—There are several methods of machining holes when using a vertical boring mill. Ordinarily, small holes are cored in castings and it is simply necessary to finish the rough surface to the required diameter. Some of the tools used for boring and finishing comparatively small holes are shown inFig. 5. SketchAshows a boring tool consisting of a cuttercinserted in a shank, which, in turn, is held in the tool slide, or in a turret attached to the tool slide. With a tool of this type, a hole is bored by taking one or more cuts down through it. The tool shown atBis a four-lipped drill which is used for drilling cored holes preparatory to finishing by a cutter or reamer. This drill would probably finish a hole to within about1/32inch of the finish diameter, thus leaving a small amount of metal for the reamer to remove. The tool illustrated atChas a double-ended flat cutterc, which cuts on both sides. These cutters are often made in sets for boring duplicate parts. Ordinarily, there are two cutters in a set, one being used for roughing and the other for finishing. The cutter passes through a rectangular slot in the bar and this particular style is centrally located by shoulderss, and is held by a taper pinp. Some cutter bars have an extension end, or “pilot” as it is called, which passes through a close-fitting bushing in the table to steady the bar. SketchDshows a finishing reamer. This tool takes a very light cut and is intended to finish holes that have been previously bored close to the required size. Sometimes a flat cutterCis used for roughing and a reamer for finishing. The reamer is especially desirable for interchangeable work, when all holes must have a smooth finish and be of the same diameter. When a reamer is held rigidly to a turret or toolslide, it is liable to produce a hole that is either tapering or larger than the reamer diameter. To prevent this, the reamer should be held in a “floating” holder which, by means of a slight adjustment, allows the reamer to align itself with the hole. There are several methods of securing this “floating” movement. (See “Floating Reamer Holders.”)
Boring with Regular Turning ToolsFig. 6. Boring with Regular Turning Tools
Boring with Regular Turning Tools
Fig. 6. Boring with Regular Turning Tools
Large holes or interior cylindrical surfaces are bored by tools held in the regular tool-head. The tool is sometimes clamped in a horizontal position as shown atA,Fig. 6, or a bent type is used as atB. Cast iron is usually finished by a broad flat tool as atC, the same as when turning exterior surfaces. Obviouslya hole that is bored in this way must be large enough to admit the tool-block.
Set of Boring Mill ToolsFig. 7. Set of Boring Mill Tools
Set of Boring Mill Tools
Fig. 7. Set of Boring Mill Tools
Turning Tools for the Vertical Boring Mill.—A set of turning tools for the vertical boring mill is shown inFig. 7. These tools can be used for a wide variety of ordinary turning operations. When a great many duplicate parts are to be machined, special tool equipment can often be used to advantage, but as the form of this equipment depends upon the character of the work, only standard tools have been shown in this illustration. The tool shown atAis a right-hand, roughing tool, and a left-hand tool of the same type is shown atB. ToolCis an offset or bent, left-hand round nose for roughing, andDis a right-hand offset roughing tool. A straight round nose is shown atE. ToolFhas a flat, broad cutting edge and is used for finishing. Left-and right-hand finishing tools of the offsettype are shown atGandH, respectively. ToolIhas a square end and is used for cutting grooves. Right-and left-hand parting tools are shown atJandK, and toolLis a form frequently used for rounding corners.
Diagrams Illustrating Use of Different Forms of ToolsFig. 8. Diagrams Illustrating Use of Different Forms of Tools
Diagrams Illustrating Use of Different Forms of Tools
Fig. 8. Diagrams Illustrating Use of Different Forms of Tools
The diagrams inFig. 8show, in a general way, how each of the tools illustrated inFig. 7are used, and corresponding tools are marked by the same reference letters in both of these illustrations. The right-and left-hand roughing toolsAandBare especially adapted for taking deep roughing cuts. One feeds away from the center of the table, or to the right (when held in the right-hand tool-block) and the other tool is ground to feed in the opposite direction. Ordinarily, when turning plain flat surfaces, the cut is started at the outside and the tool feeds toward the center, as atB, although it is sometimes more convenient to feed in the opposite direction, as atA, especially when there is a rim or other projecting part at the outside edge. The tool shown atAcould also be used for turning cylindrical surfaces, by clamping it in a horizontal position across the bottomof the tool-block. The feeding movement would then be downward or at right-angles to the work table.
The offset round-nose toolsCandDare for turning exterior or interior cylinder surfaces. The shank of this tool is clamped in the tool-block in a vertical position and as the bent end extends below the tool-block, it can be fed down close to a shoulder. The straight type shown atEis commonly used for turning steel or iron, and when the point is drawn out narrower, it is also used for brass, although the front is then ground without slope. ToolFis for light finishing cuts and broad feeds. The amount of feed per revolution of the work should always be less than the width of the cutting edge as otherwise ridges will be left on the turned surface. The offset toolsGandHare for finishing exterior and interior cylindrical surfaces. These tools also have both vertical and horizontal cutting edges and are sometimes used for first finishing a cylindrical and then a horizontal surface, orvice versa. ToolIis adapted to such work as cutting packing-ring grooves in engine pistons, forming square or rectangular grooves, and similar work. The parting toolsJandKcan also be used for forming narrow grooves or for cutting off rings, etc. The sketchK(Fig. 8) indicates how a tool of this kind might be used for squaring a corner under a shoulder. ToolLis frequently used on boring mills for rounding the corners of flywheel rims, in order to give them a more finished appearance. It has two cutting edges so that either side can be used as when rounding the inner and outer corners of a rim.
The turning tools of a vertical boring mill are similar, in many respects, to those used in a lathe, although the shanks of the former are shorter and more stocky than those of lathe tools. The cutting edges of some of the tools also differ somewhat in form, but the principles which govern the grinding of lathe and boring mill tools are identical, and those who are not familiar with tool grinding are referred toChapter II, in which this subject is treated.
Turning the Rim of a FlywheelFig. 9. Turning the Rim of a Flywheel
Fig. 9. Turning the Rim of a Flywheel
Turning a Flywheel on a Vertical Mill.—The turning of a flywheel is a good example of the kind of work for which a vertical boring mill is adapted. A flywheel should preferably bemachined on a double-head mill so that one side and the periphery of the rim can be turned at the same time. A common method of holding a flywheel is shown inFig. 9. The rim is gripped by four chuck jawsDwhich, if practicable, should be on the inside where they will not interfere with the movement of the tool. Two of the jaws, in this case, are set against the spokes on opposite sides of the wheel, to act as drivers and prevent any backward shifting of work when a heavy cut is being taken. The illustration shows the tool to the right rough turning the side of the rim, while the left-hand tool turns the periphery. Finishing cuts are also taken over the rim, at this setting, and the hub is turned on the outside, faced on top, and the hole bored.
Tool B set for Boring the HubFig. 10. Tool B set for Boring the Hub
Fig. 10. Tool B set for Boring the Hub
The three toolsA,BandC, for finishing the hole, are mounted in the turret. BarA, which carries a cutter at its end, first rough bores the hole. The sizing cutterBis then used to straighten it before inserting the finishing reamerC.Fig. 10shows the turret moved over to a central position and the sizing cutterBset for boring. The head is centrally located (on this particular machine) by a positive center-stop. The turret is indexedfor bringing the different tools into the working position, by loosening the clamping leverLand pulling down leverIwhich disengages the turret lock-pin. When all the flywheels in a lot have been machined as described, the opposite side is finished.
Diagrams showing Method of Turning and Boring a Flywheel on a Double-head Mill having one Turret HeadFig. 11. Diagrams showing Method of Turning and Boring a Flywheel on a Double-head Mill having one Turret Head
Diagrams showing Method of Turning and Boring a Flywheel on a Double-head Mill having one Turret Head
Fig. 11. Diagrams showing Method of Turning and Boring a Flywheel on a Double-head Mill having one Turret Head
In order to show more clearly the method of handling work of this class, the machining of a flywheel will be explained more in detail in connection withFig. 11, which illustrates practically the same equipment as is shown inFigs. 9and10. The successive order in which the various operations are performed is as follows: Toola(see sketchA) rough turns the side of the rim, while toolb, which is set with its cutting edge toward the rear, rough turns the outside. The direction of the feeding movement for each tool is indicated by the arrows. When toolahas crossed the rim, it is moved over for facing the hub, as shown by the dotted lines. The side and periphery of the rim are next finished by the broad-nose finishing toolscandd(see sketchB). The feed should be increased for finishing, so that each tool will have a movement of say1/4or3/8inch per revolution of the work, and the cuts should, at least, be deep enough toremove the marks made by the roughing tools. Toolcis also used for finishing the hub as indicated by the dotted lines. After these cuts are taken, the outside of the hub and inner surface of the rim are usually turned down as far as the spokes, by using offset tools similar to the ones shown atCandDinFig. 7. The corners of the rim and hub are also rounded to give the work a more finished appearance, by using a toolL.
The next operation is that of finishing the hole through the hub. The hard scale is first removed by a roughing cutterr(sketchC), which is followed by a “sizing” cutters. The hole is then finished smooth and to the right diameter by reamerf. The bars carrying cuttersrandshave extensions or “pilots” which enter a close-fitting bushing in the table, in order to steady the bar and hold it in alignment.
When the hole is finished, the wheel is turned over, so that the lower side of the rim and hub can be faced. The method of holding the casting for the final operation is shown atD. The chuck jaws are removed, and the finished side of the rim is clamped against parallelspresting on the table. The wheel is centrally located for turning this side by a plugewhich is inserted in a hole in the table and fits the bore of the hub. The wheel is held by clamps which bear against the spokes. Roughing and finishing cuts are next taken over the top surface of the rim and hub and the corners are rounded, which completes the machining operations. If the rim needs to be a certain width, about the same amount of metal should be removed from each side, unless sandy spots or “blow-holes” in the casting make it necessary to take more from one side than from the other. That side of the rim which was up in the mold when the casting was made should be turned first, because the porous, spongy spots usually form on the “cope” or top side of a casting.
Gisholt Mill equipped with Convex Turning AttachmentFig. 12. Gisholt Mill equipped with Convex Turning Attachment
Fig. 12. Gisholt Mill equipped with Convex Turning Attachment
Convex Turning Attachment for Boring Mills.—Fig. 12shows a vertical boring mill arranged for turning pulleys having convex rims; that is, the rim, instead of being cylindrical, is rounded somewhat so that it slopes from the center toward either side. (The reason for turning a pulley rim convex is to prevent the belt from running off at one side, as it sometimestends to do when a cylindrical pulley is used.) The convex surface is produced by a special attachment which causes the turning tool to gradually move outward as it feeds down, until the center of the rim is reached, after which the movement is inward.
The particular attachment shown inFig. 12consists of a special box-shaped tool-headFcontaining a sliding holderG, in which the tool is clamped by set-screws passing through elongated slots in the front of the tool-head. In addition, there is a radius linkLwhich swivels on a stud at the rear of the tool-head and is attached to vertical linkH. LinkLis so connected to the sliding tool-block that any downward movement of the tool-barIcauses the tool to move outward until the link is in a horizontal position, after which the movement is reversed. When the attachment is first set up, the turning tool is placed at the center of the rim and then linkLis clamped to the vertical link while in a horizontal position. The cut is started at the top edge of the rim, and the tool is fed downward by power,the same as when turning a cylindrical surface. The amount of curvature or convexity of a rim can be varied by inserting the clamp boltJin different holes in linkL.
The tools for machining the hub and sides of the rim are held in a turret mounted on the left-hand head, as shown. The special tool-holderAcontains two bent tools for turning the upper and lower edges of the pulley rim at the same time as the tool-head is fed horizontally. Roughing and finishing toolsBare for facing the hub, and the toolsC,D, andErough bore, finish bore, and ream the hole for the shaft.
Turning a Taper or Conical SurfaceFig. 13. Turning a Taper or Conical Surface
Turning a Taper or Conical Surface
Fig. 13. Turning a Taper or Conical Surface
Turning Taper or Conical Surfaces.—Conical or taper surfaces are turned in a vertical boring mill by swiveling the tool-bar to the proper angle as shown inFig. 13. When the taper is given in degrees, the tool-bar can be set by graduations on the edge of the circular baseB, which show the angleato which the bar is swiveled from a vertical position. The base turns on a central stud and is secured to the saddleSby the bolts shown, which should be tightened after the tool-bar is set. The vertical power feed can be used for taper turning the same as for cylindrical work.
Turning a Conical Surface by using the Combined Vertical and Horizontal FeedsFig. 14. Turning a Conical Surface by using theCombined Vertical and Horizontal Feeds
Turning a Conical Surface by using the Combined Vertical and Horizontal Feeds
Fig. 14. Turning a Conical Surface by using theCombined Vertical and Horizontal Feeds
Occasionally it is necessary to machine a conical surface which has such a large included angle that the tool-bar cannot be swiveled far enough around to permit turning by the method illustrated inFig. 13. Another method, which is sometimes resorted to for work of this class, is to use the combined vertical and horizontal feeds. Suppose we want to turn the conical castingW(Fig. 14), to an angle of 30 degrees, as shown, and that the tool-head of the boring mill moves horizontally1/4inch per turn of the feed-screw and has a vertical movement of3/16inch per turn of the upper feed-shaft. If the two feeds are used simultaneously, the tool will move a distancehof say 8 inches, while it moves downward a distancevof 6 inches, thus turning the surface to an angley. This angle is greater (as measured from a horizontal plane) than the angle required, but, if the tool-bar is swiveled to an anglex, the tool, as it moves downward, will also be advanced horizontally, in addition to the regular horizontal movement. The result is that the angleyis diminished and if the tool-bar is set over the right amount,the conical surface can be turned to an angleaof 30 degrees. The problem, then, is to determine what the anglexshould be for turning to a given anglea.
Diagram showing Method of Obtaining Angular Position of Tool-head when Turning Conical Surfaces by using Vertical and Horizontal Feeding MovementsFig. 15. Diagram showing Method of Obtaining Angular Positionof Tool-head when Turning Conical Surfaces by using Vertical andHorizontal Feeding Movements
Diagram showing Method of Obtaining Angular Position of Tool-head when Turning Conical Surfaces by using Vertical and Horizontal Feeding Movements
Fig. 15. Diagram showing Method of Obtaining Angular Positionof Tool-head when Turning Conical Surfaces by using Vertical andHorizontal Feeding Movements
The way anglexis calculated will be explained in connection with the enlarged diagram,Fig. 15, which shows one-half of the casting. The sine of the known angleais first found in a table of natural sines. Then the sine of angleb, between the taper surface and center-line of the tool-head, is determined as follows: sinb= (sina×h) ÷v, in whichhrepresents the rate of horizontal feed andvthe rate of vertical feed. The angle corresponding to sinebis next found in a table of sines. We now have anglesbanda, and by subtracting the sum of these angles from 90 degrees, the desired anglexis obtained. To illustrate:
The sine of 30 degrees is 0.5; then sinb= (0.5 ×1/4) ÷3/16= 0.6666; hence angleb= 41 degrees 49 minutes, andx= 90° - (30° + 41° 49') = 18 degrees 11 minutes. Hence to turn the casting to angleain a boring mill having the horizontal and vertical feeds given, the tool-head would be set over from the vertical 18 degrees and 11 minutes which is equivalent to about 181/6degrees.
If the required angleawere greater than angleyobtained from the combined feeds with the tool-bar in a vertical position, it would then be necessary to swing the lower end of the bar to the left rather than to the right of a vertical plane. When the required angleaexceeds angley, the sum of anglesaandbis greater than 90 degrees so that anglexfor the tool-head = (a+b) - 90 degrees.
Bullard Vertical Turret LatheFig. 16. Bullard Vertical Turret Lathe
Fig. 16. Bullard Vertical Turret Lathe
Turret-lathe Type of Vertical Boring Mill.—The machine illustrated inFig. 16was designed to combine the advantages of the horizontal turret lathe and the vertical boring mill. It is known as a “vertical turret lathe,” but resembles, in many respects, a vertical boring mill. This machine has a turret on the cross-rail the same as many vertical boring mills, and, in addition, a side-headS. The side-head has a vertical feeding movement, and the tool-barTcan be fed horizontally. The tool-bar is also equipped with a four-sided turret for holding turning tools. This arrangement of the tool-heads makes it possible to use two tools simultaneously upon comparatively small work. When both heads are mounted on the cross-rail, as with a double-head boring mill, it is often impossible to machine certain parts to advantage, because one head interferes with the other.
The drive to the table (for the particular machine illustrated) is from a belt pulley at the rear, and fifteen speed changes are available. Five changes are obtained by turning the pilot-wheelAand this series of five speeds is compounded three times by turning leverB. Each spoke of pilot-wheelAindicates a speed which is engaged only when the spoke is in a vertical position, and the three positions forBare indicated, by slots in the disk shown. The number of table revolutions per minute for different positions of pilot-wheelAand leverBare shown by figures seen through whichever slot is atC. There are five rows of figures corresponding to the five spokes of the pilot-wheel and three figures in a row, and the speed is shown by arrows on the sides of the slots. The segment disk containing these figures also serves as an interlocking device which prevents moving more than one speed controllinglever at a time, in order to avoid damaging the driving mechanism.
The feeding movement for each head is independent. LeverDcontrols the engagement or disengagement of the vertical or cross feeds for the head on the cross-rail. The feed for the side-head is controlled by leverE. When this lever is pushed inward, the entire head feeds vertically, but when it is pulled out, the tool-bar feeds horizontally. These two feeds can be disengaged by placing the lever in a neutral position. Thedirection of the feeding movement for either head can be reversed by leverR. The amount of feed is varied by feed-wheelFand clutch-rodG. When leverEis in the neutral position, the side-head or tool-bar can be adjusted by the hand-cranksHandI, respectively. The cross-rail head and its turret slide have rapid power traverse movements for making quick adjustments. This rapid traverse is controlled by the key-handlesJ.
The feed-screws for the vertical head have micrometer dialsKfor making accurate adjustments. There are also large dials atLwhich indicate vertical movements of the side head and horizontal movements of the tool slide. All of these dials have small adjustable clipscwhich are numbered to correspond to numbers on the faces of the respective turrets. These clips or “observation stops” are used in the production of duplicate parts. For example, suppose a tool in face No. 1 for the main turret is set for a given diameter and height of shoulder on a part which is to be duplicated. To obtain the same setting of the tools for the next piece, clips No. 1, on both the vertical feed rod and screw dials, are placed opposite the graduations which are intersected by stationary pointers secured to the cross-rail. The clips are set in this way after the first part has been machined to the required size and before disturbing the final position of the tools. For turning a duplicate part, the tools are simply brought to the same position by turning the feed screws until the clips and stationary pointers again coincide. For setting tools on other faces of either turret, this operation is repeated, except that clips are used bearing numbers corresponding to the turret face in use.
The main turret of this machine has five holes in which are inserted the necessary boring and turning tools, drills or reamers, as may be required. By having all the tools mounted in the turret, they can be quickly and accurately set in the working position. When the turret is indexed from one face to the next, binder leverNis first loosened. The turret then moves forward, away from its seat, thus disengaging the indexing and registering pins which accurately locate it in any one of the five positions.The turret is revolved by turning crankM, one turn of this handle moving the turret1/5revolution or from one hole to the next. The side-head turret is turned by loosening leverO. The turret slide can be locked rigidly in any position by leverPand its saddle is clamped to the cross-rail by leverQ. The binder levers for the saddle and toolslide of the side-head are located atUandV, respectively. A slide that does not require feeding movements is locked in order to obtain greater rigidity. To illustrate, if the main tool slide were to feed vertically and not horizontally, it might be advisable to lock the saddle to the cross-rail, while taking the vertical cut.
The vertical slide can be set at an angle for taper turning, and the turret is accurately located over the center of the table for boring or reaming, by a positive center stop. The machine is provided with a brake for stopping the work table quickly, which is operated by lifting the shaft of pilot-wheelA. The side-and cross-rails are a unit and are adjusted together to accommodate work of different heights. This adjustment is effected by poweron the particular machine illustrated, and it is controlled by a lever near the left end of the cross-rail. Before making this adjustment, all binder bolts which normally hold the rails rigidly to the machine column must be released, and care should be taken to tighten them after the adjustment is made.
Turning a Gear Blank on a Vertical Turret LatheFig. 17. Turning a Gear Blank on a Vertical Turret Lathe
Fig. 17. Turning a Gear Blank on a Vertical Turret Lathe
Examples of Vertical Turret Lathe Work.—In order to illustrate how a vertical turret lathe is used, one or two examples of work will be referred to in detail. These examples also indicate, in a general way, the class of work for which this type of machine is adapted.Fig. 17shows how a cast-iron gear blank is machined. The work is gripped on the inside of the rim by three chuck jaws, and all of the tools required for the various operations are mounted in the main and side turrets. The illustrationshows the first operation which is that of rough turning the hub, the top side of the blank and its periphery. The toolsAfor facing the hub and upper surface are both held in one tool-block on the main turret, and toolA1for roughing the periphery is in the side turret. With this arrangement, the three surfaces can be turned simultaneously.
The main turret is next indexed one-sixth of a revolution which brings the broad finishing toolsBinto position, and the side turret is also turned to locate finishing toolB1at the front. (The indexing of the main turret on this particular machine is effected by loosening binder lever n and raising the turret lock-pin by means of leverp.) The hub, side and periphery of the blank are then finished. When toolsBare clamped in the tool-blocks,they are, of course, set for turning the hub to the required height. The third operation is performed by the tools atC, one of which “breaks” or chamfers the corner of the cored hole in the hub, to provide a starting surface for drillD, and the other turns the outside of the hub, after the chamfering tool is removed. The four-lipped shell-drillDis next used to drill the cored hole and then this hole is bored close to the finished size and concentric with the circumference of the blank by boring toolE, which is followed by the finishing reamerF. When the drill, boring tool and reamer are being used, the turret is set over the center or axis of the table, by means of a positive center stop on the left-side of the turret saddle. If it is necessary to movethe turret beyond the central position, this stop can be swung out of the way.
Turning Gasoline Engine Flywheel on Vertical Turret Lathe—First PositionFig. 18. Turning Gasoline Engine Flywheel on Vertical Turret Lathe—First Position
Fig. 18. Turning Gasoline Engine Flywheel on Vertical Turret Lathe—First Position
Turning Gasoline Engine Flywheel—Second PositionFig. 19. Turning Gasoline Engine Flywheel—Second Position
Fig. 19. Turning Gasoline Engine Flywheel—Second Position
Figs. 18and19illustrate the turning of an automobile flywheel, which is another typical example of work for a machine of this type. The flywheel is finished in two settings. Its position for the first series of operations is shown inFig. 18, and the successive order of the four operations for the first setting is shown by the diagrams,Fig. 20. The first operation requires four tools which act simultaneously. The three held in tool-blockAof the turret, face the hub, the web and the rim of the flywheel, while toolain the side-head rough turns the outside diameter. The outside diameter is also finished by broad-nosed toolbwhich is given a coarse feed. In the second operation, the under face of the rim is finished by toolc, the outer corners are rounded by tooldand the inner surface of the rim is rough turned by a bent toolB, which is moved into position by indexing the main turret. In the third operation, the side-head is moved out of the way and the inside of the rim is finished by another bent toolB1. The final operation at this setting is the boring of the central hole, which is done with a barChaving interchangeable cutters which make it possible to finish the hole at one setting of the turret.
Diagrams showing How Successive Operations are Performed by Different Tools in the TurretFig. 20. Diagrams showing How Successive Operationsare Performed by Different Tools in the Turret
Diagrams showing How Successive Operations are Performed by Different Tools in the Turret
Fig. 20. Diagrams showing How Successive Operationsare Performed by Different Tools in the Turret
The remaining operations are performed on the opposite side of the work which is held in “soft” jawsJaccurately bored to fit the finished outside diameter as indicated inFig. 19. The tool in the main turret turns the inside of the rim, and the side-head is equipped with two tools for facing the web and hub simultaneously. As the tool in the main turret operates on the left side of the rim, it is set with the cutting edge toward the rear. In order to move the turret to this position, which is beyond the center of the table, the center stop previously referred to is swung out of the way.
Floating Reamer Holders.—If a reamer is held rigidly in the turret of a boring mill or turret lathe, it is liable to produce a hole which tapers slightly or is too large. When a hole is bored with a single-point boring tool, it is concentric with the axis of rotation, and if a reamer that is aligned exactly with the boredhole is fed into the work, the finished hole should be cylindrical and the correct size. It is very difficult, however, to locate a reamer exactly in line with a bored hole, because of slight variations in the indexing of the turret, or errors resulting from wear of the guiding ways or other important parts of the machine.
To prevent inaccuracies due to this cause, reamers are often held in what is known as a “floating” holder. This type of holder is so arranged that the reamer, instead of being held rigidly, is allowed a slight free or floating movement so that it can follow a hole which has been bored true, without restraint. In this way the hole is reamed straight and to practically the same size as the reamer.
Two Types of Floating Reamer HoldersFig. 21. Two Types of Floating Reamer Holders
Two Types of Floating Reamer Holders
Fig. 21. Two Types of Floating Reamer Holders
There are many different designs of floating holders but the general principle upon which they are based is illustrated by the two types shown inFig. 21. The reamer and holder shown to the left has a ball-shankAwhich bears against a backing-up screwBinserted in the end of holderCthrough which the driving pin passes. The lower end of the reamer shank is also spherical-shaped atD, and screw-pinEsecures the shell reamer to this end. It will be noted that the hole in the shank for pinEis “bell-mouthed” on each side of the center and that thereis clearance atFbetween the shank and reamer shell; hence the reamer has a free floating action in any direction. This holder has given very satisfactory results.
The holder shown to the right is attached to the face of the turret by four fillister-head screws. SleeveCis held in plateAby means of two steel pinsBwhich are tight in plateAand made to fit freely in bayonet groovesD. Reamer holderEfloats on sleeveC, the floating motion being obtained through the four steel pinsGextending into driving ringF. Two of the pins are tight in the holderEand two in sleeveC. The faces of sleeveC, driving ringF, and reamer holderEare held tightly against each other by means of springHwhich insures the reamer being held perfectly true. SpringHis adjusted by means of nutIwhich is turned with a spanner wrench furnished with each holder. The reamer is so held that its axis is always maintained parallel to the center of the hole, and, at the same time, it has a slight self-adjusting tendency radially, so that the hole andreamer will automatically keep in perfect alignment with each other.