In the case of a piloted counterbore or stepped reamer, the ratio of the hole diameters (d1:d2) should conform to the established ratio furnished by the tool manufacturer.

(h) Efficient Milling

To minimize machining costs avoid blind keyways (a), or keyways extending up to a square shoulder (which would Involve needlessly expensive machining). While design (C) represents an improvement, it is better still to add a curved exit, which permits use of a more sturdy milling cutter (d). The best design is a Woodruff key (e).

To reduce setup time, a keyway on a tapered surface (a) should be parallel to the shaft axis, if possible, as in (b).

The flat-bottomed slot in the fork-like work-piece (a), requires a large travel on the part of the milling cutter. By curving the bottom so as to match the radius of the cutter, as in (b), the tool travel (and hence machining time) are significantly reduced.

The milling of a flat surface with a projection (a) requires cuts in two directions and careful machining to avoid a slight mismatch between the milled surfaces. It possible, raise one surface intentionally, as in (b), in order to reduce the precision needed for the milling operation.