Elementary machine shop practice; a text book presenting the elements of the machinists' trade

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1921 Excerpt: ...ft. per minute. For soft machinery steel use grade M, grit #36 vitrified. For same kind of stock, but long slender work, use grade L, grit #36 vitrified. For cast iron, when a high finish is wanted use grade #4, grit #36 elastic. For chilled cast iron use grade #4, grit #36 elastic. For brass and copper use grade #4, grit #36 elastic. For tool steel and case hardened machine steel use grade K, grit #36 vitrified. The above list is not given as a suggestion that no other wheels shall be used for the materials mentioned, but rather as a guide to the learner in selecting wheels; in each case mentioned, the particular wheel has been used on the class of work mentioned, and has given good results. Work Speed.--The wheel speed mentioned above, that is 5000 feet per minute, is a good average rate of travel for the wheel; in modern grinding practice this item varies from 5000 to 7000 feet per minute with good results; the work speed varies to a more marked extent and the following list is presented as a guide for the learner in selecting the speed at which the surface of the work should run: Soft machinery steel 35 feet per minute. Hard machinery steel 35 feet per minute on the roughing cut, and 60 feet per minute on the finishing cut. Case hardened machinery steel, and tool steel 35 feet per minute. Cast iron 55 feet per minute. Bronze and brass 75 feet per minute. In small plants the worker often finds himself so placed that he may not keep several wheels on hand, as the most rapid production is not demanded, but rather a reasonable production, with a small outlay for wheels; if an operator may have but one wheel a grade M grit #36 will be found generally serviceable; with the smaller wheels one is not limited so closely in the matter of the number of wheels to b...