Fig. 36. Boring Tool
The shape of tool t for boring is quite different from one used for outside turning, as shown by [Fig. 36]. The cutting end of a solid type of tool is forged approximately at right angles to the body or shank, and the top surface is ground to slope away from the working part w of the cutting edge, as with practically all turning tools. The front part or flank, f is also ground away to give the edge clearance. This type of tool is clamped in the toolpost with the body about parallel with the lathe spindle, and ordinarily the cutting edge would be about as high as the center of the hole, or a little below, if anything. When starting a cut, the tool is brought up to the work by moving the carriage and it is then adjusted radially to get the right depth of cut, by shifting the cross-slide. The power feed for the carriage is then used, the tool feeding back through the hole as indicated by the arrow, [Fig. 34]. In this case, as with all turning operations, the first cut should be deep enough to remove the hard outer scale at every part of the hole. Usually a rough-cored hole is so much smaller than the finished size that several cuts are necessary; in any case, the last or finishing cut should be very light to prevent the tool from springing away from the work, so that the hole will be as true as possible. Boring tools, particularly for small holes, are not as rigid as those used for outside turning, as the tool has to be small enough to enter the hole and for this reason comparatively light cuts have to be taken. When boring a small hole, the largest tool that will enter it without interference should be used to get the greatest rigidity possible.
Fig. 37 (A) Setting Outside Calipers.
(B) Transferring Measurements to Inside Calipers.
(C) Micrometer Gage
Fig. 38. Standard Plug Gage