Fig. 1653.
For broad feed finishing cuts the shape of tool shown in [Fig. 1653] is employed, the cutting edge near the two corners being eased off very slightly with the oilstone. The amount of clearance should be very slight indeed, only just enough to enable the tool to cut as is shown in the figure, by the line a a. The amount of front rake may be varied to suit the nature and hardness of the metal, and the tool should be held as close in as possible to the tool clamp.
Fig. 1654.
Smoother work may be obtained in shaping and in planing machine tools when the tool is carried in a holder, such as in [Fig. 1654], which is taken from The American Machinist because in this case any spring or deflection either in the tool or in the shaper head acts to cause the tool to relieve itself of the cut instead of digging in, as would be the case were the tool put in front of the tool post as in [Fig. 1654]. In finishing large curves this is of great importance, because to obtain true and smooth curves it is necessary to shape the tool to cut upon the whole of the curve at once, and this gives so great a length of cutting edge, that the tool is sure to chatter if held in front of the tool post.
