208 THE MACHINE-SHOP \ . x X SIDE ELEVATION BACK £L£I//\T/OA/ \ are clamped in pairs, and lie parallel in recesses at the opposite end, where they are brought up against an abutment piece. The ends to be bevelled project beyond the vees, where they are milled with a cutter, divided, in order to permit of readjustment with packing as the edges wear. Example of a Box Jig- fixture.—Figs. 42 and 43 give the principal elements of a fixture by Messrs. Ruston & Hornsby, Ltd., of Lincoln, used in machining the body of a check valve. Its characteristic feature is the provision made for drill- ing a large number of holes at different angles. The valve, enclosed in the fix- ture, is located by a flange which enters the shallow recess in the bottom, and is secured by the jig cover. Fig. 43.—Drilling Bush set at Angles in a Locating Block The inside of the COVCr IS recessed to receive a flange on the opposite end of the valve body. The four bushed holes arranged in a circle in the bottom and in the cover guide the drills for the bolt holes in the flanges. Two other holes are drilled at angles through the bushes A and B, to permit of which the fixture has bevelled feet at a and b. During the vertical drill- ing, bevelled packing pieces are inserted under these edges. The round hole c receives bushes that interchange for drill- ing and tapping holes. The oblong recess D re- ceives the locating block, Fig. 44.—Hinged Cover for a Fixture containing Four Drilling , , , , ,£ >. Bushes at different Heights Shown detached (tig. 43 ), that carries a drilling bush at angles in two directions. The fixture is then stood at the required angles on a bevelled support. The holes E and F receive bushes to guide drills for holes in the body. Fig. 44 is the cover of a fixture through which holes are drilled at different heights in the body of a feed pump. It is hinged at the left, and clamped at the right with an eye-bolt in an open slot. Nuts are not run off their bolts, only slackened.