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AN experienced model engineer, like a good cook, is a practical person who can often produce acceptable results from odds and ends with few tools. Both may work with equipment which is far from ideal. Until a generation ago, cooks got magnificent results with primitive ovens. Model engineers performed splendid work on elementary lathes. The principle holds today, for it is results that matter in a workshop, as in a kitchen. In some hands_, a fork is as good as an electric whisk, just as in others files and scrapers will do some of the work of machine tools. Recognition of these age-old principles should encourage newcomers; for there are many small tools whose making requires only stock materials and standard screws and bolts,. And the few tools that a beginner possesses for drilling, sawing and filing. The sketches show some examples of tools that can be made with this limited equipment although for some operations a lathe would normally be used.

The first example, shown at A, is a substitute for a toolmaker’s clamp. This clamp is one of the basic tools of a workshop, and is often made as an exercise in technique. In the standard type, there are holes to tap and threads to cut. The heads of the screws are knurled.


Tools by Drilling and Filling




In the substitute, these operations are avoided by the drilling of clearance holes and the use of standard screws and nuts. As shown, you drill two clearance holes for the screws in the bottom piece of square bar, and one clearance hole and a dimple in the top piece. If you wish, the ends of the jaws can be hacksawed and filed at an angle. You tighten the clamp with a spanner on the nuts. Diagram B shows clamps that can be used for light work of uniform thickness. Work of this sort often calls for several clamps; besides being large and heavy, toolmakers’ clamps are usually too few in number. For the clamp at Bl, you bend a piece of rectangular steel at right-angles and drill it with the flat piece for the screw and nut. For the clamp at B2, you turn the material U-shape and drill it. This clamp should be squeezed in the vice, so that it has to be opened by pnsmg with a screwdriver to slip on the work. Then there is reduced strain on the screw. The clamp at B3 is made from thick rectangular material, drilled for springiness and slit with a hacksaw. The jaws can be smoothed with a thin file. The tap wrench shown at C is a favourite with some toolmakers. I know professional turners whose preference in lathe carriers is for the type illustrated. Both these tools can be made from square mild steel bar, even by novices. You should clamp the pieces for drilling to keep the holes in line. File matching Vs in the pieces for the tap wrench to locate and grip the tap by two corners of its square. Use a round file to produce shallow radii for work held in the carrier. You can turn each of the handles of the tap wrench in a lathe by holding one end in a four-jaw chuck with the other end centred and supported by the tailstock centre .


With three pieces of flat steel 1/16 in. or 3/32in. thick, you can make a gauge, as at D, for checking the angle of lips on a twist drill, to be certain that both are the same. Two pieces are used for the stock and one piece is used for the blade. The stock is spaced by a washer at the opposite end. You can set the blade to a good drill, and then scribe it from the stock, as a guide for resetting on subsequent occasions. Sketch E shows two other easilymade small tools, a depth gauge and a V-block. You make the stock of the depth gauge from two pieces of flat material held by screws; the rod is gripped between them. The two thick pieces for the V-block are spaced by washers on two bolts. A scribing block can be made as at F, with the base drilled for countersunk screws, on which the scribing bar is held by nuts. Make this bar from silver steel, hardened and tempered, or from mild steel, by bending it down and drilling, so that a sewing needle can be held by solder.


58. Collet Chuck Fittings
Aug 01, 2017

THE main advantages of collet chucks, over other types, are the firmness and the accuracy with which small diameters are held. It is why the normal equipment of instrument lathes and precision lathes includes sets of collet chucks covering ranges of standard sizes. Work and tools rods, drills, spindles and cutters can all be set up without difficulty.Production lathes which are used for repetition machining of small components from barstock, are also fitted with collet chucks; and many toolroom lathes have them as standard or as additional equipment. When lathes are not fitted with cullet chucks, other means of holding work and tools must often be contrived-like split bushes, or halved blocks which can be gripped in jaw chucks; or split mandrels with taper threads at the nose ends which can be closed by ring nuts. All these are satisfactory for one-off jobs or for short runs of several components. Within their limits, they equal cullet chucks and show the advantages these have over other types. Often from such an example comes the determination to fit the lathe with a proper set of collet chucks-when time permits. For the project is seen as one involving a considerable amount of precision work. This is true if one goes about the job in the usual way: but by following the method described here, the result is the same for practical purposes, with much less time and effort expended. The idea is to use a holder for collets in a small., four-jaw independent chuck, in which it can be quickly set to run truly. The holder can be in mild steel, left normal, or casehardened. Alternatively, cast steel can be used, unhardened-or hardened, then tempered to dark-straw colour.


Collet Chuck Fittings



In each case, treatment is to choice. If the lathe has a hollow spindle, the holder can be as at A, with a parallel diameter to grip in the chuck, a shoulder to abut to the jaws, and a reduced nose end which can be set true by indicator. In machining, important work should be left until the chucking diameter is finished and the material has been rechucked nose’ end outwards. This end is reduced, faced and centred. Then a drill is run through the material, followed by a boring tool-and a reamer if to hand. After this, the bore is opened for a short distance, then the end is tapered with the topslide at 15 deg. If the holder is hardened, grinding and lapping operations follow. At their front ends collets are tapered to suit the holder; and their rear ends are threaded so that each will take a sleeve into which is screwed the drawbolt passing through the lathe spindle. Pulling on the drawbolt by a nut or a handwheel draws the collet into the holder. Collets can be in good mild steel, and much work can be avoided by using bolts, left normal, or casehardened. Using a bolt, it is set true at the neck in the independent chuck, as at B. With the topslide at 15 deg., the head is machined to angle V.



If the collet is to be hollow, the bolt is reversed in the chuck and centred and drilled from the back. Otherwise, it goes straight into the holder to finish the front end for the job. Centred from the tailstock, it is drilled, then reamed or bored, according to circumstances. Then it is cross-drilled and slit. If rod is used, the collet can be turned and threaded on a set-up as at C. If the lathe has a solid spindle, a holder for collets must be as at D , threaded for a nut, through which the nose of the collets can extend. Screws WX and a plate should be fitted, as collets sometimes stick. Then they can be easily loosened. Outside machining or grinding operations can be done at any time to a holder on a mandrel as at E; and collets can be slit in a pair of blocks as at F. For boring, the blocks are held in the independent chuck; to form a slot, their faces are filed. In use, the blocks are gripped in the vice at positions YZ. 



57. Lathe Milling
Jul 16, 2017

A CENTRE lathe with vertical equipped for many operations that would otherwise require a universal milling machine. For you can make single-point tools perform the same operations as multiple-tooth cutters by reducing the rate of feed so that a dig-in cannot occur. You can make the tools from round and square bits and pieces of silver steel rod, to mount in holders in chucks or to fit in the taper in the lathe spindle. The cost in cash is small. If time presses, and you must keep to bare essentials, there are several easy-to-make holders that can be made from mild steel bar. They can be case-hardened or left soft. For frequent use, you should case-harden them before they become dented and worn.


Lathe Milling




According to need, you can set the vertical slide squarely or at angles on the cross-slide. The angle plate you can mount on the vertical silde, flat or sloping. To put on cuts, you have the lead-screw for the saddle, and the screws for the cross and vertical slides. Any of these screws can be used to move work past a rotating cutter; and so, besides making set-ups at compound angles, you can feed work in any of three planes at right-angles. Diagram A shows some typical operations which are performed by running tools in the chuck with the work mounted on the vertical slide. For boring A 1, you can sometimes USC an ordinary boring tool in the independent chuck. If the hole is small, you can make a . round-shanked tool from silver steel rod and mount it in a holder. In each case, set the tool by adjusting it in the chuck jaws. Fix the vertical slide and cross-slide by the screws to their gib pieces; or wedge the slides with packing to prevent movement. Feed the work by the saddle. For facing A2, you can fit a round tool in a reamed hole in a rectangular mild steel holder, fixing it through a grub screw. Adjust the circle swept by the tool by setting the tool and the holder. Apply cut this to the bed or retaining its position with lead-screw nut. Feed the work with the cross-slide or vertical slide. For slotting or grooving A3, you can use an end mill in a holder in the chuck, setting the tool to run concentrically. Apply cut again from the saddle, and feed the work by the cross-slide or vertical slide. The ordinary end mill has two cutting edges so that the end of the tool appears as at Bl. To re-sharpen it, you need an accurate square edged grinding wheel. When this creates a problem, the solution is to make an end mill with a single cutting edge, B2. Then you can re-sharpen it on any flat face on a grinding wheel. The single-edged end-mill will do the same job as a double-edged type when it is run fast with slow feed for the work.



You can make a holder to mount round-shank tools in the independent chuck as at B3. Chuck two pieces of rectangular mild steel bar; face and centre the end and drill through undersize. Finish the bore with a standard drill or a reamer. The abutting edges of the pieces you can ease with a file for the holder to grip the shanks firmly. To keep the halves of such a holder together, turn the ends circular and machine the grooves for circlips, B4. Make the circlips from coils of springs. A shank pushes into the holder with a friction grip.

Another holder for a chuck is shown at C, upper diagram. In this the tool is clamped by a grooved cotter made from a bolt. Fit the bolt first. Drill and ream the hole for the tool. Then cut the head off the bolt. The holder at C, lower diagram, has a taper shank to fit in the lathe spindle. The rear end can be tapped for a draw-bolt. You slit the other end with a saw to line WX for clamping. A holder for square tools, diagram D, consists of a centre block with side-plates YZ fixed by countersunk screws.  



56. Dividing in the Lathe
Jun 25, 2017

IT is a great convenience, even on a simple lathe, to be able to mark round components with the commonly-required numbers of divisions, such as four or six, as are necessary when making squares and hexagons; and to make other numbers of equal spacing in a neat and regular manner, such as to provide serrations on the edges of small bosses and knobs by which a finger grip can be obtained on fittings. It is true, square and hexagon mateterial can be obtained in ranges of standard sizes; but these do not cover all requirements-such as an exceptionally large size, or if a fitting is needed with a circular flange larger than the hexagon, or if a square or hexagon is required on the end of a shaft for key or spanner manipulation. To make squares or hexagons to a high degree of precision, milling is, of course, necessary. But for general purposes careful checking by micrometer if desired is quite satisfactory. When the lathe has means of dividing, the material is machined slightly larger than the size over the corners, a pointed tool being mounted sideways in the tool holder and set touching the work.



Dividing in the Lathe





Using Four-jaw Chuck

At each located position the tool is traversed by saddle or top slide, leaving a scribed line. To produce the flats, the material between the lines is filed away, the job being removed from the chuck and held in the vice, still on the bar or in soft jaws to avoid damage.

When equipment includes a four jaw chuck and the jaws overlap the flat surface of a bed, squares can be marked by holding each jaw to a support bar, as at A. Such a bar can be from round mild steel, say about 5/8 in. dia., its length having been obtained by checking with inside calipers from the bed to the under-sides of a pair of jaws when these are horizontal: The bar should be reasonably to length, and it can be used either side of the bed, but on one side only for one job. Another method, applicable in the absence of a four-jaw chuck and also to work between centers is to clamp a straight bar to the work, as at B . Distances X-Xl can be equalized with a surface gauge or scribing block and a mark made on the work with the too!; then the bar can be set horizontal again, after rotating half a turn, for making the second mark. Quarter markings are made with the bar set vertically with a square from the bed. Pressure can be kept on the work from the tailstock to prevent movement.




Quicker Method

Much more speedy and wider in scope, however, are drilled back plates, as at C, in conjunction with a simple plunger device for holding. Indexing for drilling can be done from a change gear which can be mounted on a mandrel in the chuck, key-pinned and held by a setscrew. A locating bar in the tool holder fits between the gear teeth, as at D. When there are two chucks, 12 spacing on one back plate and 40 on the other will give the following divisions most commonly needed: on the first, 2, 3, 4, 6, 12; on the second, 2, 4, 5, 8, 10, 20, 40. The first can be obtained from a 48 or 60 tooth gear; the second from a 40 or 80 tooth gears. The guide for a drill about 1/8 in. dia. should be from silver steel, and hardened. A countersunk screw fixes it to a mild-steel bar which is mounted from the back on a block or wall, or from the bench or stand at the front of the bed, as at E. For a bench lathe, indexing can be as at F, a cross-bracket fixed behind the lathe carrying a pivoted bar with a silver steel pin. Normally, the bar holds by its own weight, or a wing nut and screw can be fitted at Y for tightening.  



There are numerous ways of measuring inside diameters, depending on the accuracy necessary and whether the check is to verify an identifiable size, test size exactly, or compare diameters for dimensions or general truth. For simple checks of identifiable sizes a rule can be used, or a rule and calipers, or for more precise work calipers and a slide gauge or outside micrometer. Thus, to check the bore of a piece of tubmg a rule can be used direct, or the size can be taken on friction grip calipers and these checked on a rule.

Where a rule cannot be used, as for the bore of a ball race which has radiused ends? Calipers are essential, with verification made on a rule, since the size will be standard and not subject to variation of a few thou. On the same principle, calipers and outside micrometers can be used to higher accuracy. For example, a . Check on the diameter of a cylinder which could be standard, or plus 0.010 in., would need to be made with some care, and with a micrometer to verify the caliper setting. The same is true also if there is a possibility of confusion between millimeter and inch dimensions, when checking on a rule could leave the issue in doubt.  



Measuring Internal Diameters



Friction grip calipers are subject to limitations in setting, but the screw type, as at A, will check a diameter to within about 0.002 in. when used correctly with a light touch. To obtain the size of a bore, one leg is positioned at X, and the calipers are rocked to carry the other leg to and fro across the shortest distance and on a diameter, Y-Y 1. Adjustments are made until there is just-detectable friction across the shortest distance, and then the calipers are verified in a micrometer, adjusting this until similar friction obtains on the calipers, when the size can be read in the normal way on the micrometer. The principle is applicable when an internal diameter is being bored in a lathe; but the micrometer should be initially set several thou. Undersize, and care exercised in trial cuts so as not to overrun the dimension. As the bore nears size, all cuts should be run right through, since this avoids variations in depth of cut and spring of the tool, which could result in a bore being bell-mouthed. If a very large diameter is to be tested, the tailstock centre can be rhn up, a rule laid on the point, and a diameter marked on the face of the work with pencil or chalk so that the calipers can be kept across the diameter, as at Y-Yl. For checking machined bores, alternatives to calipers are telescopic gauges and adjustable ball gauges, B and c, the latter for very small dimensions. A telescopic gauge is entered in the bore, expanded, then its sliding plunger locked from the handle; a ball gauge is expanded in the bore from the handle. Both are checked for size (or set) with an outside micrometer.


A gauge with a slight taper, as at D. affords means of checking a bore being finished in a lathe. Mild steel can be used for the gauge, the top diameter (0.750 in.) turned to finished size and the taper carried down several thou. Less (0.740in.) in any convenient length, Z. A flat is filed and divided according to the difference in thou. Between the ends, so that for each mark that enters, the bore increases by 0.001 in. End gauges employed for bores must be provided with radii, as at E (right), not with flat ends (left), the comers of which would prevent an accurate check. This applies to the outside ends of gauges with sliding plungers, as at F, the inner ends being flat for feeler gauges to be placed between them, checking over a range. Bodies of such gauges can be mild steel; plungers hardened silver steel.


AS in the case of diameters, there is not always the need for precision on width and length measurements-but when it is demanded accuracy is no less important on the one than the other. Given a micrometer, diameters can easily be checked as work proceeds; but if width and length measurements have habitually been made with a rule-with all the variations that that implies -the need for greater precision may find one unprepared. Yet accuracy when machining widths and lengths is relatively easy to achieve. On a lathe having a topslide feed with graduated collar readings can be taken from this for positioning tools for facing cuts, and in some instances longer lengths can be obtained using the leading screw. Again, very accurate work can be done using simple gauges for setting tools, and this is often practised as occasion demands even on lathes fitted with feed collars. For old-type lathes without feed collars, or on which screws are worn, the use of gauges is virtually imperative to ensure precision and speed up production. The principle is as illustrated at A, where a piece of material is turned with two shoulders.


Accurate Length Machining



The lengths could be measured with a rule,; but a much more precise and speedier way is to machine the lengths slightly oversize then employ two gauges Xl, X2, to set the tool for finishing cuts. With the lathe stopped, a gauge is held to its respective shoulder and the tool set just to touch; then the gauge is removed and the cut taken at the precise position. In most workshops there are numerous objects of reasonable precision, such as drill shanks, silver steel rod, pieces of ground tool steel, etc., in standard sizes which can be used as gauges. If a micrometer is available material may also be turned or filed to size, and then it is possible to add to or delete from nominal dimensions for particular fits. For example, if a flange is nominally 1/8in. wide, but for a clearance fit 0.002 in. endplay is desirable, then the gauge could be made 1/8 in. minus 0.002 in. Again, if necessary, widths and lengths can be obtained falling between inch fractions, which would demand estimation on a rule. The chuck face or a jaw can be used as a datum for gauges, but one extra is required since the two gauges, Yl, Y2, only locate the end face and one shoulder; another would be needed for the second shoulder. Besides this, the gauges are in general longer and would require to be made specially.


On second operations, however, measurements can be made from the chuck face or jaws, though when a holder is used it is best to work from its face which, as at B, should be flat and large enough to take the gauges squarely. As at C, a recess can be machined to depth by finishing the interior over-length, then using a gauge to set the tool for the outside facing cut. Where a groove must be accurately located from the end face, either of two methods can be employed. The tool edge may be set flush with the end face, then taken in by feed collar reading, or a step gauge can be used, C. The principle is applicable to backfacing flanges, as at D, where the gauge is a simple adjustable type set by using a block of suitable thickness in conjunction with a straight-edge. A variation of such a step gauge -snipped or sawn, then filed from sheet metal-is as at E for obtaining the over-all dimension of a pair of flanges on a shaft machined between centres. Beyond the flanges, the shorter lengths can be obtained with other gauges. Locating from the saddle, as at F, an adjustable stop can be fitted to the headstock to take gauges in the space.



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