Fig. 1113.
Fig. 1114.
Under ordinary conditions that in the form of tool shown in [Fig. 1113][15] is best for brass work, the face a being horizontal or slightly depressed towards the point. Boring tools require very little bottom rake, and the cutting points should be as rounded as they can be made without chattering. On wrought iron the top rake may be as much as is consistent with strength, and water should be freely applied to the cut. For cast iron the best form of tool is that shown in [Fig. 1114], the edge a being parallel with the bore of the hole, and the feed being a coarse one, taking a very light cut when finishing.
[15] From “The Complete Practical Machinist.”
Fig. 1115.