Modern Machine-Shop Practice Part 107

[Ill.u.s.tration: Fig. 1504.]

Suppose the slide to be on its return stroke in the direction of L, and F be rotated as denoted by the arrow, then the pawl C will be actuating wheel A as denoted by its arrow, but if C be moved over so as to engage D as denoted by the dotted outline, then with the slide moving in the same direction, C will pull D in the direction of arrow K', and wheel A will be actuated in the opposite direction, thus reversing the direction of the feed while still causing it to actuate on the return stroke.

Since the feed wheel A must be in a fixed position with relation to the work table feed screw, and since the height of this table varies to meet the work, it is obvious that as the work table is raised the distance between the centres of A and F in the figure is lessened, or conversely as that table is lowered the distance between those centres is increased; hence, where the work table has much capacity of adjustment for height, means must be provided to adjust the length of rod E to suit the conditions. This may be accomplished by so arranging the construction that the rod may pa.s.s through its connection with wheel F, in the figure, or to pa.s.s through its connection with B.

Fig. 1505 represents a shaper that may be driven either by hand or by belt power. The cone pulley shaft has a pinion that drives the gear-wheel shown, and at the other end of this gear-wheel shaft is a slotted crank carrying a pin that drives a connecting rod that actuates the sliding bar, or ram, as it is sometimes termed. The fly-wheel also affords ready means of moving the ram to any required position when setting the tool or the work.

Fig. 1506 represents a shaping machine by the Hewes and Phillips Iron Works, of Newark, N.J. The slide or ram is operated by the Whitworth quick return motion, whose construction will be shown hereafter. The vice sets upon a knee or angle plate fitting to vertical slideways on the cross slide, and may be raised or lowered thereon to suit the height of the work by means of the crank handle shown in front. The vice may be removed and replaced by the supplemental table shown at the foot of the machine. Both the vice and the supplemental table are capable of being swivelled when in position on the machine. The machine is provided with a device for planing circular work, such as sectors, cranks, &c., the cone mandrel shown at the foot of the machine bolting up in place of the angle plate.

[Ill.u.s.tration: Fig. 1505.]

[Ill.u.s.tration: Fig. 1506.]

HOLDING WORK IN THE SHAPER OR PLANER VICE.--The simplest method of holding work in a shaper is by means of a shaper vice, which may be employed to hold almost any shape of work whose size is within the capacity of the chuck. Before describing, however, the various forms of shaper vices, it may be well to discuss points to be considered in its use.

The bottom surface _a_ _a_, Fig. 1507, of a planer vice is parallel with the surfaces _d_, _d'_ and as surface _a_ is secured to the upper face of the slider table shown in figure, and this face is parallel to the line of motion of the slide A, and also parallel with the cross slide in that figure, it follows that the face _d_ is also parallel both with the line of motion of slide A and with the surface of the slider table.

Parallel work to be held in the vice may therefore be set down upon the surface _d_ (between the jaws), which surface will then form a guide to set the work by. The work-gripping surfaces _b_ and _e_, Fig. 1507, of the jaws are at a right angle to surface _a_, and therefore also to _d_, therefore the upper surface of work that beds fair upon _d_, or beds fair against _b_, will be held parallel to the line of motion X of the tool and the line Z of the feed traverse. Similarly the upper surfaces A, B of the gripping jaws are parallel to _a_ _a_, hence they may be used to set the work true with the line of feed traverse. The sliding jaw, however, must be a sufficiently easy fit to the slideways that guide it to enable it to be moved by the screw that operates it, and as a result it has a tendency to lift upon its guideways so that its face _e_ will not stand parallel to _b_ or at a right angle to _d_. In Fig.

1508, for example, is a side view of a vice holding a piece of work W, the face _f_ of the work being at an angle. As a consequence there is a tendency to lift in the direction of C. If the jaw does lift or spring in this direction it will move the work, so that instead of its lower face bedding down upon face _d_, Fig. 1507, it will lie in the direction of H, Fig. 1508, while its face parallel to _f_, instead of bedding fair against the face of jaw J, will lie as denoted by the line _g_, and as a result the work will not be held fair with either of those faces and the value of faces _b_, _d_ and _e_ in Fig. 1507 is impaired.

This lifting of the movable or sliding jaw is prevented in some forms of chuck, to be hereafter described, by bolts pa.s.sing through which hold it down, but the tendency is nevertheless present, and it is necessary to recognise it in treating of chucking or holding work in such vices.

[Ill.u.s.tration: Fig. 1507.]

[Ill.u.s.tration: Fig. 1508.]

The work gripping face _b_, Fig. 1507, of the fixed jaw, however, is not subject to spring, hence it and the surface _d_ are those by which the work may be set. The work, however, is held by the force of the screw operating the sliding jaw, hence the strain is in the direction of the arrow P in Fig. 1508, which forces it against the face of the fixed jaw.

All the pressure that can be exerted to hold work down upon the surface _d_, Fig. 1507, is that due to the weight of the work added to whatever effort in that direction there may be induced by driving the work down by blows upon surface _d_ after the jaws are tightened upon the work.

This, however, is not to be relied upon whenever there is any tendency for the work not to bed down fair. It follows, then, that surface _b_ of the work-gripping jaw is that to be most depended upon in setting the work, and that the surface that is to act as a guide at each chucking should be placed against this surface unless there are other considerations that require to be taken into account.

[Ill.u.s.tration: Fig. 1509.]

For example, suppose we have a thin piece of work, as in Fig. 1509, and the amount of surface bearing against the fixed jaw is so small in comparison to its width between the jaws that _e_ would form no practical guide in setting the work. If then the edges of such a piece of work were shaped first the face or faces may or may not be made at a right angle to them, or _square_ as it is termed. But if the faces were shaped first, then when the work was held by them to have the edges shaped there would be so broad an area of work surface bedding against the jaw surface, that the edges would naturally be shaped square with the faces.

In cases, therefore, where the area of bedding surface of the work against the faces of the jaws is too small to form an accurate guide and the work is not thick enough to rest upon the surface _d_, Fig. 1507, it is set true to that surface by a parallel piece.

If the work is wide or long enough to require it, two parallel pieces must be used, both being of the same thickness, so that they will keep the work true with the surface _d_.

[Ill.u.s.tration: Fig. 1510.]

Pieces such as P, Fig. 1510, are also used to set work not requiring to be parallel. Thus in figure are a number of keys placed side by side and set to have their edges shaped, and piece P is inserted not only to lift the narrow ends of the keys up, but also to maintain their lower edges fair one with the other, and thus insure that the keys shall all be made of equal width.

They are also serviceable to interpose between the work and the vice jaws when the work has a projection that would receive damage from the jaw pressure.

[Ill.u.s.tration: Fig. 1511.]

Thus in Fig. 1511 the work W has such a projection and a parallel piece P is inserted to take the jaw pressure. By placing the broadest work surface _g_ against the fixed jaw the work will be held true whether the movable jaw springs or not, because there will be surface _g_ and surface H guiding it.

[Ill.u.s.tration: Fig. 1512.]

But if the work were reversed, as in Fig. 1512, with the broadest surface against K, then if K sprung in the direction of C, the work would not be shaped true.

[Ill.u.s.tration: Fig. 1513.]

When the work is very narrow, however, the use of a parallel piece to regulate its height is dispensed with, and the top surface B of the jaw, in Fig. 1513, is used to set the work by. A line is marked on the work surface to set it by and a surface gauge is set upon the face B, its needle point being set to the line in a manner similar to that already explained with reference to chucking work in the lathe.

All work should be so set that the tool will traverse across the longest length of the work, as denoted by the tool in Fig. 1502, and the arrow marking its direction of traverse.

The general principles governing the use of the shaper vice having been explained, we may now select some examples in its use.

Fig. 1514 represents a simple rectangular piece, and in order to have the tool marks run lengthwise of each surface (which is, as already stated the most expeditious) they must be in the direction of the respective arrows. In a piece of such relative proportions there would be little choice as to the order in which the surfaces should be shaped, but whatever surface be operated on first, that at a right angle to it should be shaped second; thus, if _a_ be first, either _b_ or _d_ should be second, for the following reasons.

[Ill.u.s.tration: Fig. 1514.]

All the surfaces have sufficient area to enable them to serve as guides in setting the work, hence the object is to utilize them as much as possible for that purpose. Now, suppose that surface _a_ has been trued first, and if _c_ be the next one, then the bedding of surface _a_ upon the vice surface or the parallel pieces must be depended upon to set _a_ true while truing _c_. Now the surfaces _b_ and _d_ may both, or at least one of them, may be untrue enough to cause the work to tilt or cant over, so that _a_ will not bed fair, and _c_ will then not be made parallel to _a_. It will be preferable then to shape _a_ first and at the second chucking to set _a_ against the stationary jaw of the vice, so that it may be held true.

[Ill.u.s.tration: Fig. 1515.]

The sliding jaw will in this case be against face _c_, and if that face is out of true enough to cant the work so that _a_ will not bed fair, then a narrow parallel piece may be inserted between the sliding jaw and the work, which will cause _a_ to bed fair. The third face should be face _c_, in which case face _a_ will rest on one surface and face _b_ will be against the fixed jaw, and there will be two surfaces to guide the work true while _c_ is being trued. In this case also, however, it is better to use a parallel piece P, Fig. 1515, between the work and the sliding jaw, so as to insure that the work shall bed fair against the fixed jaw; and if necessary to bring up the top surface above the jaws, a second parallel piece P' should be used.

[Ill.u.s.tration: Fig. 1516.]

Suppose now that we have a connecting rod key to shape, and it is to be considered whether the faces or the edges shall be shaped first. Now if the side faces are out of parallel it will take more filing to correct them than it will to correct the same degree of error in the edges; hence it is obviously desirable to proceed with a view to make all surfaces true, but more especially the side faces. As the set of the key while shaping these faces is most influenced by the manner in which the fixed jaw surface meets the work, and as an edge will be the surface to meet the fixed jaw faces when the side faces are shaped, it will be best to dress one edge first, setting the key or keys, as the case may be, as was shown in Fig. 1510, so as to cut them with the tool operating lengthways of the key; one edge being finished, then one face of each key must be shaped, the key being set for this purpose with the surfaced edge against the fixed jaw. As the width of the key is taper, either a chuck with a taper attachment that will permit the sliding jaw to conform itself to the taper of the key must be used (vices having this construction being specially made for taper work as will be shown hereafter), or else the key must be held as in Fig. 1516, in which K represents the key with its trued edge against the fixed jaw, at P is a piece put in to compensate for the taper of the key, and to cause the other edge to bed firmly and fairly against the fixed jaw.

The first side face being trued, it should be placed against the fixed jaw while the other edge is shaped. For the remaining side face we shall then be able to set the key with a trued edge against the fixed jaw, and a true face resting upon a parallel piece, while the other edge will be true for the piece P, Fig. 1516, to press against, and all the elements will be in favor of setting the key so that the sides will be parallel one to the other, and the edges square with the faces.

In putting in the piece P, Fig. 1516, the key should be gripped so lightly that it will about bear its own weight; piece P may then be pushed firmly in with the fingers, and the vice tightened up.

[Ill.u.s.tration: Fig. 1517.]

If there are two keys the edges and one face may be trued up as just described, and both keys K, Fig. 1517, chucked at once by inverting their tapers as shown in figure. But in this case unless the edges are quite true they may cause the keys not to bed fair on the underneath face, and the faces therefore to be out of parallel on either or both of the keys. If there are a number of keys to be cut to the same thickness it may be done as follows:--

[Ill.u.s.tration: Fig. 1518.]

Plane or shape first one edge of all the keys; then plane up one face, chucking them with one planed edge against each vice jaw, and put little blocks (A, B, C, D, Fig. 1518) between the rough edges; then turn them over, chuck them the same way and plane the other face, resting them on parallel pieces; then plane the other edges last.

In place of the small blocks A, B, C, D, a strip of lead, pasteboard, or wood, or for very thin work a piece of lead wire, may be used.

[Ill.u.s.tration: Fig. 1519.]

[Ill.u.s.tration: Fig. 1520.]

Cylindrical work may be held in a vice chuck, providing that the top of the vice jaws is equal in height to the centre of the work, as in Fig.

1519, a parallel piece being used to set the work true. When, however, the work is to be shaped at one end only, it is preferable to hold it as in Fig. 1520, letting its end project out from the side of the chuck. In some vices the jaws are wider than the body of the chuck, so that cylindrical work may be held vertical, as in Fig. 1521, when the end is to be operated upon.

Fig. 1522 represents a simple form of shaper or planer chuck, such chucks being used upon small planing machines as well as upon shaping machines.

[Ill.u.s.tration: Fig. 1521.]