Modern Machine-Shop Practice Part 175

The length C of the [V] of the template must not be longer than from 4 to 6 inches, or it will be liable to spring or twist from its own weight. This template is not intended to be used in any sense as a straight-edge to test the truth of the length of the ways, but rather as one to test their width apart, and the correctness of the angles. The top surface A B should be quite true with the [V]'s, being equidistant from them, so that by testing that surface with a spirit-level it may be known whether the ways are level either crosswise or lengthwise.

The [V]'s of the template require to have red marking on them so as to mark the ways when the template is moved, and show that the ways accurately fit to the template, which is highly important.

In planing the table or platen it is essential to bear in mind that the area to be planed on the [V] side is always small in comparison with that to be planed on the other or work-holding side of the table, and as the planing of this latter surface is sure to cause the casting to alter its form, it is necessary to plane it first, so that the alteration of form may occur before and not after the [V]'s have been planed.

In chucking the table to plane its work-holding surface, the packing pieces must be used as described for the bed, and the bolts placed as there described.

Both bed and table being planed they require to be fitted together (no matter how expertly the planing has been done) if a really first-cla.s.s job is to be made of them. In doing this it is essential that the bed be supported at the same points as it will be when the machine is put to work, for in large or long casting the deflection or bending from its own weight is sufficient to have an important practical effect. The same fact will also apply to the table and even to the cross slide, even though the latter be heavily ribbed and but, say, 5 feet long.

If, therefore, the bed is to be supported by legs, its guideways or [V]'s should be fitted after the legs are attached. The bed must be carefully levelled so that the ways may stand horizontally true, which may be tested by placing the template A B in Fig. 2570 in place and applying a spirit-level first across and then lengthwise of the upper surface of the template.

If the bed rests upon a foundation at several points in its length it should be rested at those points while being fitted and carefully levelled as before, the template and spirit-level being tried at every two or three feet of the bed length.

To test the width of the [V]'s and their widths apart in the fitting, the template A B, Fig. 2570, must be used in connection with red marking, but to true the lengths of the ways a surface plate about 4 feet long and slightly wider than the width of one side of the ways must be used, and if the template and the surface plate show the ways true they will be of the correct width, of correct angle and true planes. But this does not insure that the two ways are in line one with the other, and for this purpose separate test blocks are necessary, because the template is too narrow in width to give a good test, and cannot be made wider, because in that case its own weight would cause it to spring or deflect to suit any error in the work.

[Ill.u.s.tration: Fig. 2571.]

These test blocks are simply two pieces of metal, such as shown in Fig.

2571. The lengths of these blocks should be about 8 inches, and the best way to obtain them true and exactly alike is to make one block and then cut it into two. They possess an advantage not possessed by a template that spans both ways, inasmuch as they may be turned end for end in each way and thus test the accuracy of the angles of each way.

Again, both may be placed in one way, and by various applications in connection with straight-edge, surface plate, and level they will test the truth of the ways, both individually and one with the other in a better manner than by any other method.

Fig. 2572 represents the various positions of the [V] blocks for the testing, A, B, C, D, E, F, G, H, representing the blocks; straight-edges may be placed as at I, at J, and at K, and if the ways are true the straight-edge, lightly coated with marking, should have contact clear across the upper surface of both [V]-blocks, and a spirit-level placed on the straight-edge (in each position of the same) should show them to be level.

The surface P, on which uprights or standards on that side of the plane, rest, being planed with the [V]-ways will be true with them, and the uprights may be erected thereon, their base surfaces being fitted to P until the standards stand truly vertical and parallel in their widths apart. In testing these uprights they should be bolted home as firmly as they will be when finally erected, as they will be liable to alter their set if bolted up more firmly than when tested. These front surfaces should be at a right angle to the length of the bed [V]-ways, and this may be tested by placing a straight-edge across their surfaces and testing it with a square rested against the edge of the planer table.

The method of erecting planers at the Pratt and Whitney Company's shops is as follows:--

To test the [V]'s, a plate P, Fig. 2573, is applied as shown, its lugs _a_, _a_^{1} fitting to corresponding sides of the two [V]s; as B, B. In Fig. 2573 the test is made by inserting thin pieces of tissue paper between _a_, _a_^{1} and the [V]-sides, the friction with which the paper is held showing the nature of the fit. Thus, if the paper will move easily at one end and is tight at the other end of either of the lugs _a_, _a_^{1} the fit is shown to be defective. When the fit on these sides is corrected, the plate P is turned around, as in Fig. 2574, and from a similar tissue-paper test, the other sides are corrected.

Thus the outside angles of the two [V]s are fitted to the same angle; inside angles are also fitted to the same angle. But it will be observed that it does not follow that the inside angles of the [V]s are of the same degree of angle as are the outside halves or angles, unless the two lugs _a_, _a_^{1} of the plate P have equal angles. It is on this account that the test is made by tissue paper, rather than by the bearing marks produced by rubbing P along the [V]s, since that might in time wear the angles _a_, _a_^{1} out of true. The same plate P may be used to true the male [V]s on the work-holding table of the machine, as is shown in Figs. 2575 and 2576, where the table is seen upside down, as is necessary in order to apply the plate. Here, again, the outside angles or halves of the [V]s are fitted from the same [V] (_a_^{1}) of the plate, so that the fit of the table will be true to the bed, even though the angle on one side of the [V]-ways were not precisely correct, and there is less liability to error than would be the case were a male and female plate used instead of a single plate. The alignment next in importance is that of the uprights, standards, or side frames of a planing machine, and to enable the correct erection of these, the device A, Fig. 2577, is employed. It consists of a solid plate fitting into the [V]-ways of the planer-bed and having two steps, B and C, which receive the side frames to be erected. The width D is the width apart of the side frames, and the side surfaces of the steps (as G) are vertical to the centre line of the [V]-ways of the bed, so that the side frames may be rested against G on one side, and the corresponding surface on the other step. The surfaces E, F are at a right angle to the [V]-ways of the bed, so that when the side frames are against E, F they will be set square across the machine. The top face of the plate A is planed parallel to the [V]s of the plate, so that in addition to resting each side frame against the surfaces (as F G) a square may be rested on plate A and applied to their trued surfaces, and thus may these side frames be set true and square, both one with the other, and with the ways in the bed, without the use of stretched lines and straight-edges, which secures greater accuracy and saves considerable labor.

[Ill.u.s.tration: Fig. 2578.]

All the smaller parts of the machine may then be erected true to the bed or the side frames, as may be required, and if it be a small planer, in which the bed rests upon feet, all that will be necessary in setting the machine in position to work is to set the surface of the work-table level. But in the case of a large heavy planer a solid foundation must be built for the bed, because it will spring, bend, and deflect from its own weight, and thus the side frames, as well as the bed, may be thrown out of true and alignment. Fig. 2578 is a side and plan view of the foundations for a planer, showing the bed-plate in position upon the same.

[Ill.u.s.tration: _VOL. II._ =TESTING PLANER BEDS AND TABLES.= _PLATE XI._

Fig. 2572.

Fig. 2573.

Fig. 2574.

Fig. 2575.

Fig. 2576.

Fig. 2577.]

The stone blocks forming the base of the foundation require themselves to rest upon a solid base, and not upon a soil or gravel that is liable to sink beneath them. The brickwork above them is best laid in cement, which should be properly set before the planer bed is placed in position. Near the centre of the bed, and directly beneath the cross-slide, is shown a screw jack, to take up any sag of the bed, and cause the [V]s to have a good bearing directly beneath the cutting tool, which is essential to prevent the table from springing from the pressure of the tool cut.

FITTING UP AND ERECTING A LATHE.--The first operation will be to true the bed or shears. If the lathe has raised [V]s on the bed it will be sufficient to true them only, without truing the flat surfaces. The bed should during the fitting be supported at the same points as it will be when in use.

[Ill.u.s.tration: Fig. 2579.]

The method of aligning the lathe heads at the Pratt and Whitney Company's workshops is as follows: Fig. 2579 is a side and an end view of a part of a lathe shears A, with the tailstock B thereon. To the bore of the tailstock there is closely fitted an arbor C, accurately turned in the lathe, and having at the end D and at E two short sections of enlarged diameter. A plate F is fitted to the inside [V]s of the shears (upon which [V]s the tailstock sits). This plate carries a stand G, and a second gauge or stand G. Stand G fits at its foot into a [V] provided in F, as shown, the object of which is to so hold G to F that its (G's) face will stand parallel to arbor C. The stand is so adjusted that a piece I may be placed between C and G and just have contact with both, and it is obvious that if this is found to be the case with the tailstock and the stand placed at any position along the bed, the arbor C, and, therefore, the bore of the tailstock, must be true, sideways, to the inside [V]s of the lathe shears. The testing, however, is made at the enlarged sections D and E, G of course being firmly bolted to F. To test the height of the arbor C from the [V]s, and the parallelism in that direction, stand H is provided. It carries a pointer or feeler K, whose end is adjusted to just touch the enlarged sections D and E of C, it being obvious that when the degree of contact is equal at these two sections, with the tailstock and the plate F moved to various positions along the bed, the adjustment or alignment in that direction is also correct. The adjustment and corrections may then be made with the headstock of the lathe in place of the tailstock, the arbor fitting into the bored boxes of the lathe and extending from it, and having two sections of the same diameter, as sections E in the figure. Now, suppose that in the test thus made the bar C proves to stand true in some locations, but not in others, upon the bed; then it is proof that it is the [V]s that require correction, while the tailstock is in error in all cases in which the error is constant, with the tailblock moved in various positions along the shears.

In some practice the heads are bored after being fitted to the ways, and in this case the boring bar may be supported by standards fitting to the lathe bed, running in bearings, and not on centres. There should be three of these bearings, one at one end of the head, and as close to it as convenient, another at the other end, as close as will permit the insertion of the cutters, and the third as far from the second as will permit the insertion on the bar and between them of a pulley to drive the bar, which must be splined to receive a feather in the pulley, so that the bar may be fed through its bearings and through the pulley to the cut. After the live head has been bored the tailstock or back-head may be bored from the other end of the bar, so that the standards will not require to be moved on the bed until the boring is completed. The bar may be fed by hand, or an automatic feed motion may be affixed to one of the standards. The heads being secured to the bed while being bored, there is no liability of error in their alignment, because, even if the holding bolts spring the heads in clamping them to the bed, the holes will be true when the heads are firmly home upon the bed, as they will be when in use, whereas under this condition such will not be the case if the holes for the spindles are bored before the seats are planed and fitted.

The feed screw must be placed quite parallel to the [V]s or guides of the bed, or otherwise the pitches of threads cut in the lathe will be finer than they should be, and the screw will bind in the feed nut, causing undue wear to both.

The method employed to test the truth of lathe shears and heads in the David W. Pond Works, at Worcester, Ma.s.sachusetts, is as follows:--

[Ill.u.s.tration: Fig. 2580.]

The planing, both of the lathe shears and of the heads, being done as accurately as possible, the heads are provided with a mandrel or arbor, to the end of which is secured the device shown in Fig. 2580, in which A is a hollow cylindrical piece having a threaded and split end, so that by means of a nut the bore may be closed to tightly fit the arbor referred to; B, B are two arms, a sliding fit in A, to enable their adjustment for the width of lathe [V]s, and having a flat place on one side, as at C C, to receive the pressure of a locking device D, by means of which B, B may be fastened in their adjusted positions; E, E are cylindrical arms, a sliding fit in B, B, also having flat sides, and capable of being secured in their adjusted positions by means of locking devices F, F.

[Ill.u.s.tration: Fig. 2581.]

[Ill.u.s.tration: Fig. 2582.]

Fig. 2581 is an end view of the device in position on a lathe tail stock, and Fig. 2582 is an enlarged view (being half full size) of the devices at the lower end of arms or rods E, E.

At the lower ends of E, E are provided two pieces G, G, which are capable of adjustment to fit the [V]s H, H of the lathe, as follows:--

The middle pins I are fast in the arms J, but are pivoted in G, the end pins, as K, are pivoted in G, are flat where they pa.s.s through J, and threaded to receive the nuts, L, of which there are four, two to each piece G. By operating these nuts, G may be adjusted to bed fair on the angles on the lathe [V]s H. At M are two fixed pins which afford a fulcrum, at N and O respectively, to four index needle arms. Two of these index arms only are seen in the cut, marked respectively P and Q, which are pivoted at N. Two similar pointer or needle arms are on the other side of M, being behind P and Q, these two being pivoted respectively at O. At the lower end of P is a point resting in the centre of the nut, and similarly the end of Q rests in the centre of the nut on that side. Similarly the two needles not seen have pointed ends resting in the centre of the nuts marked respectively L. Between G and J are two springs placed back to back, which act to hold G away from J.

But it will be seen that if either end of G be forced towards J, as by pa.s.sing over a projection on the [V] H, then the pin K, will push nut L, and this will raise the end of the pointer or needle to a corresponding degree, and the pointer being pivoted (as at N), its upper end will move and denote on the graduated index R that there is an error in the lathe [V], the amount of the error being shown multiplied on account of the leverage of the needle arms from the pivots.

The pieces G being adjusted to bed fairly on the lathe [V]s, the heads of the lathe are moved along the lathe shears, and if the [V]s are true to angle the upper ends of the needles will remain stationary, a projecting part of a [V] will, however, cause the needle point to move toward E, while a depression on a [V] would cause the springs K to move G in, keeping it in contact with the [V], while the needle point would move away from E. To maintain the needle arms in contact with the nut heads L, springs S are employed. Variations in the widths apart of the [V]s on either side of the shears would obviously be shown in the same manner, the defect being located by the needle movement. The corrections are made from the contact marks of the heads, caused by moving the heads along the [V]s and by careful sc.r.a.ping.

Notwithstanding that every care and attention may be taken to make a lathe true in the process of manufacture, yet when the whole of the parts are a.s.sembled it is found essential to test the truth of the finished lathe, because, by the multiplication of minute errors the alignment of the lathe, as a whole, may be found to need correction. A special inspector is therefore employed to test finished machines before they leave the works, and in Fig. 2583 is represented the device employed for testing the alignment of the line of centres of lathes.

Upon the face of the face plate and near its perimeter there are turned up two steps, as denoted by B and C. The tail-spindle is provided with a stud S, which fits in the place of the dead centre, and carries what may be termed a double socket, one-half of which (as F) envelops the stud S, while the other half (A) envelops and carries a rod R. These two halves are in reality split sleeves, with set screws to close them and adjust the fit. By means of the screws E, the sleeve F may be made a tight working fit upon S, while, by means of screws G, sleeve A may be made to firmly grip the rod R, which may thus be securely held while still capable of being swung upon stud S. Upon the outer end of the rod R is another sleeve I, which is also split and secured to the rod R by means of screws corresponding to those shown at G. It also carries a pin, upon which a disk K is pivoted, and a lug through which the adjusting screw V is threaded. Upon K is a lug which has on one side of it the end of a spring T, and it is obvious that by operating V the disk K will be rotated upon its central pin. K carries two lugs, L and M, the latter being threaded and split. These two lugs receive a sleeve N, threaded into M, and a close plain fit in L. The small end of this sleeve is split and is threaded slightly taper, and is provided with the nut P.

Through this sleeve pa.s.ses a needle Q Q, one end of which is bent as shown, and it is obvious that by s.c.r.e.w.i.n.g nut P upon N the sleeve will be closed and will tightly grip the needle Q Q. Now, suppose that the head of N is operated, and it will move endwise through L and M, carrying with it the needle Q Q, which will remain firmly clasped in the sleeve; or suppose that screw V is operated, and K will revolve, carrying with it the needle Q Q, which will still remain firmly gripped, and it follows that there is thus obtained a simple means of adjusting the needle without releasing it.

[Ill.u.s.tration: Fig. 2583.]

The application of the instrument is as follows: To test if the head and tailstocks are of equal height from the bed, the instrument is set and adjusted exactly as shown in the engraving, the needle being adjusted to just touch the diameter of the step at B. The rod R is then swung around so that the needle comes opposite to the same step B at the bottom of the face plate, and if the needle just touches there also the adjustment for tailstock height is correct. Similarly for testing if the tailstock is set true sideways the needle may be tried in the same manner and upon the same step, but upon the two opposite sides of the face plate, instead of at the top and bottom. It now remains to test if the tailstock is in line in a horizontal direction with the live spindle, and this is done by reversing the needle end for end in the sleeve N, and setting it to just touch the face C of the turned step on the face plate, and if it just touches at the top and bottom as well as at the two sides the tail-spindle is obviously in line. It may be observed, however, that if an error in any one direction is found, it is necessary to go through the whole series of tests in order to precisely locate the error. Suppose, for example, that the needle, being adjusted as in the engraving to just touch the step at B, does not touch it when tried at the bottom of the plate, then the error may be caused in three ways--thus, in the first place, the whole tailstock may be lower than the headstock; in the second place, the front end of the tailstock may be too low; or, in the third place, the back end of the tailstock may be too high. If the first was the cause, the test with the needle point tried with face C would show correct. If the second or third was the cause of the error, the needle point when tried to face C would touch when applied at the top, but would not touch when tried at the bottom of the face plate. Another case may be cited. For example, suppose the needle applied as shown touched at the bottom but not at the top of the step B, then the test with the needle reversed would show whether the whole tailstock was too high, or whether the front end only was too high, or the back end too low. There is one excellent feature in this device to which attention may be called, which is that the tests are made on as large a diameter of face plate as possible, which shows the errors magnified as much as possible.

The same device is used to test if the cross slide of the carriage or saddle is at a right angle to the lathe shears, the method of its application being as shown in Fig. 2584. The split sleeve A receives in this case a rod R, which is laid in the slideway S of the carriage or saddle, and a long rod H carries the needle-holding devices. The rod R is held fair against the slideway, and the face of the sleeve A is held against the edge of the carriage or saddle. The needle Q is then adjusted to just touch the edge D of the lathe bed. When this adjustment is made the rod H is swung over to the right and the coincidence of the needle point again tried with the edge of the lathe bed, the cross slideway being at a right angle when the needle point touches the edge D of the lathe bed when tried on the left hand, and also on the right hand, of the carriage. The stiffening rod U is brought under tension by a nut operated against a lug on X. To counterbalance the overhanging weight of the rod H and its attachments, a rod carrying a weight W is employed. It is obvious that the truth of the operation depends wholly upon the straightness and parallelism of the enlarged sections P of the rod R, upon keeping the end face of A in contact with the carriage at Z, and upon the correct adjustment of the needle to the edge of the lathe bed.

[Ill.u.s.tration: Fig. 2584.]

SETTING LINE SHAFTING IN LINE.--The following method of adjusting line shafting or setting it in line, as it is termed, is that generally adopted in the best practice.

[Ill.u.s.tration: Fig. 2585.]

[Ill.u.s.tration: Fig. 2586.]