tral with the hole B in the work, Fig. 132. When in operation the cut is against the fixture, thereby holding the work rigidly against its face.

Fig. 134 shows two views of a fixture which, although very simple and inexpensive to construct, has much to commend it. It is used for milling the dovetail in the end of the casting shown in Fig. 132, and will accommodate six castings at a time. It consists of the two end angle-brackets B B, the central locating- and clamping-arbor C, and the locating-bar 0. The end

brackets BB are first bored out and the hubs faced, and then they are placed on an arbor and the base of each is milled with the tongues E E in line with each other. A square hole is now let into the face of each bracket at F as shown, and finished to size and in line by clamping both brackets together and forcing a broach through the unfinished holes. The locating-bar G is of square tool steel, finished all over for its entire length, to fit nicely within the holes in the face of the brackets. The width of the bar is made to fit the square channel E, Fig. 132, previously milled in the castings or work. When the fixture is in use

the bracket B at the right is clamped securely on the millertable, and the one at the left slipped off the arbor C. The six castings I are then slipped on to the arbor with the square milled channel of each down, so that the locating-bar G rests within them. The left bracket is then slipped on and the nut K tightened slightly. By tightening the screws in the ends J of the casting, the channels are clamped to the locating-bar G. Nut H

is then tightened securely and the bracket firmly clamped to the table: By the use of the vertical attachment and of an angular cutter, the six castings are milled and finished to the shape shown at F, Fig. 132, and at K, Fig. 134.

The points to be considered when designing fixtures for milling in one operation a number of small parts of the type here shown are as follows: First, the number which can be handled

i

to the best advantage; second, the manner of presenting the work to the cutters, and, lastly, the most expeditious and reliable means for locating and holding the work rigidly while being milled.

FIXTURE FOR USE IN GANG-MILLING.

A type of fixture used extensively for gang-milling, where wide surfaces or a number of depressions are to be milled in the face of castings that have not been previously machined, is shown

R

Р

M

S

FIG. 136.

in Figs. 135 and 136. Although of the simplest construction, it represents a useful type of milling fixture for the milling of a large variety of work that it would be difficult to machine rapidly by any other means. This fixture is used for the milling of

the type of casting shown at H, Fig. 137, which consists of four channels H H H H in the face, and of the square channel I in one end; requiring two separate operations; both being accom

plished on the one fixture. Fig. 135 shows a section of the plan and side view, and also an end view of this fixture which handled eight castings at once. It consists of one large casting M having two half-round depressions running down its entire length as clearance for the projections on the back of the work. The top is planed true with the base as a squaring surface for the work, and ends in a square shoulder at N for the work to locate against. The work is held in position by clamps at R R so placed as to clamp two castings, as shown at PP. The holes for the bolts are counterbored at the back to allow the heads to clear the miller-table, as at T T in the side view, Fig. 135. The work is fastened as shown, and the square channel in the end is milled. When all the castings have gone through this operation, the four channels are finished by relocating and fastening the work to the fixture and setting a gang of mills. The cross-slide of the miller-table is then clamped, the depth of the cut set, and the castings finished.

FIXTURE USED IN FACE-MILLING.

Another type of simple milling-fixture is shown in the two views of Fig. 138. Although somewhat similar to that shown in

Fig. 135 it is used for a distinctly different class of milling; that is, face-milling. The sketch shows it being used for ends V

V of castings like Fig. 139. This casting is first set up on the planer and the dovetailed slide-surfaces U U are planed to gauge. The fixture is constructed to handle two castings at once, they being located sidewise by forcing the side of one of the dovetailed surfaces Z against the angular-faced locating-lugs XXXX as shown, and endwise against the squared and faced projections Y Y at the back. The castings are held in position by two clamps each, as at C C C C, and the heads of the bolts are let into the base, as at A A in the side view. The ends of the castings are faced by a large cutter-holder, with self-hard

U

FIG. 139.

ening steel cutters set into the rim, so that a roughing and finishing cut can be taken at the same time. When one end of the casting has been faced, they are reversed, relocated, and the other ends are faced.

When the large variety of machine parts, both small and large, which can be machined in exact duplication of each other by the use of just such simple and inexpensive fixtures as are here shown is considered, it is surprising that these methods of manufacture had not been adopted more extensively. By this we mean in the small shop; for in the large shops, unless the machines or appliances are manufactured under patents, it is absolutely necessary to manufacture by the interchangeable system in order to meet competition.