Machinery's Handbook

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1914 edition. Excerpt: ...turns are indexed by taking two holes in the i8-ho!c circle ior each degree. In this case,---3%, which indicates that the index crank must be turned three 9 full revolutions, and then 8 degrees more are indexed by moving 16 holes in the i8-hole circle. To index for 11'-degrees, for example, first turn the index crank one revolution, this being a g-degree movement. Then to index lVi degrees, move the index crank 5 holes in the i8-hole circle (4 holes for the two whole degrees and one hole for the V2 degree equals the total movement of 5 holes). Below is shown how this calculation may be carried out to plainly indicate the movement required for this angle: nV4 dcg. = 9 deg. + 2 deg. + dcg. 1 turn + 4 holes + 1 hole in the 18-hole circle. Should it be required to index only degree, this may be done by using the 27hole circle. In this circle a three-hole movement equals one degree, and a one-hole movement in that circle thus equals degree, or 20 minutes. Assume that it is required to index the work through an angle of 48 degrees 40 minutes. Below is plainly shown how this calculation may be carried out: 48 deg. 40 min.-4s deg. + 3 dcg. + 40 min. 5 turns-(-9 holes+ 2 holes in the 27-hole circle. Angular Values of One-Hole Moves--B. S. Index Plates Approximate Indexing for Angles.--The following general rule for approximate indexing of small angles is applicable to any index head requiring 40 revolutions of the index crank for one revolution of the work. Rule: Divide 540 by the total number of minutes to be indexed. If the quotient is approximately equal to the number of holes in any index circle available, the angular movement is obtained by moving the crank one hole in this index circle; but if the quotient is not approximately equal,...