. Railway mechanical engineer . Necessary Trior to the advent of tap grinding machinery nearly alltaps were ground by hand with a resultant lack of uni-formity in taper and clearance. The accompanying dia-gram. Fig. 1. shows a section of a four-flute tap with each ing off. The flute .4, at the left, is ground with a straightline clearance sufticient to have the of the fluteactually clear and not drag. This calls for an angle of 15deg., as indicated, and results in a weak cutting edge, butthe strongest possible with a straight line clearance at theheel. The flute B. at the toj). show
. Railway mechanical engineer . Necessary Trior to the advent of tap grinding machinery nearly alltaps were ground by hand with a resultant lack of uni-formity in taper and clearance. The accompanying dia-gram. Fig. 1. shows a section of a four-flute tap with each ing off. The flute .4, at the left, is ground with a straightline clearance sufticient to have the of the fluteactually clear and not drag. This calls for an angle of 15deg., as indicated, and results in a weak cutting edge, butthe strongest possible with a straight line clearance at theheel. The flute B. at the toj). shows a 15-deg. convex clear-. Fig. 3—No. a Grand Rapids Tap Grinding Machine ance. A glance shows this to be excessive. Flute C, at theright, shows a straight line clearance of five degrees, andnearly half of the flute at the back is not cleared at all, leav-ing the tap to ride on that portion and keep the front of theflute from cutting. Flute D, at the bottom, shows a perfectgrind for ordinar}- work. It is a five-degree convex clear-ance and shows that with this small Ijut sufficient clearanceangle at the ( utting edge, the back is perfectly cleared. 406 RAILWAY ENGINEER Vol. 94, No. 6 In addition to the correct clearance of taps a uniformangle of taper for all flutes is necessary-. The results of dif-ferent tapers obtained by hand grinding are indicated in r- k Felt tVashers Bronze Bushing g vpm
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectrailroadengineering
