Fig. 899.
Fig. 900.
Suppose, then, we fasten the piece of work to the angle plate as shown in [Fig. 899], and face off the surface c, and bore the hole h, the work being set true with its surface, or to a line, by the aid of a surface gauge, as may be required. We then turn surface c down to meet the surface of the angle plate, fasten it to the same with bolts and plates and setting it as before, and on turning its surface a we shall have the two surfaces a and c at a right angle to one another. We then turn the surface a down upon the angle plate and bolt it again as before. But we have now to set it so that the surface c shall be quite parallel with the surface of the chuck plate. This we may do by placing one or more parallel strips behind it, as at s s, in the plan view, [Fig. 900], setting the work so that it binds the parallel strips tight against the chuck plate along their full lengths; or we may measure the distance of c from the chuck plate surface with a pair of inside calipers; or we may turn the bent end of a surface-gauge needle outwards and gauge the work as shown in the plan view, trying the work all along. On turning the surface d, [Fig. 897], we shall have three of the surfaces done at right angles and with c and d parallel.
Fig. 901.
It is obvious that the surface d may be turned down on the angle plate and bolted as before, the surface a being set parallel to the chuck plate surface as before, and all four of these surfaces will be finished true as required. Next come the two end surfaces and the pin i. For f and the pin i we chuck the work on the angle plate, as shown in the plan view, [Fig. 901], p, p representing the clamping-plates. The angle plate will here again serve to hold the work true one way, and all we have to do to set it true the other way is to fasten a pointer in the tool post and bring it up to just touch the corners of the work at the outer end, as at k. Now run the carriage up so as to bring the pointer to position l, and when the work is so set that all four corners just touch the pointer, tried in their two positions, without touching the cross-feed screw, the work is true, and the end surface e and hole g may be turned; e will then be at a true right angle to the four faces, a, b, c, d, while g will be axially true with them.