Machinery's Handbook, 31st Edition
696 Tapers Measuring Tapers with V-Block and Sine-Bar.— The taper on a conical part may be checked or found by placing the part in a V-block that rests on the surface of a sine-plate or sine-bar as shown in the accompanying diagram. The advantage of this method is that the axis of the V-block may be aligned with the sides of the sine-bar. Thus, when the tapered part is placed in the V-block, it will be aligned perpendicular to the transverse axis of the sine-bar.
A
D
D 2
C
B
The sine-bar is set to angle B = ( C + A /2) where A /2 is one-half the included angle of the tapered part. If D is the included angle of the precision V-block, the angle C is calculated from the formula: sin sin ( D ⁄ 2) sin ( A ⁄ 2) C = If dial indicator readings show no change across all points along the top of the taper sur face, then this checks that the angle A of the taper is correct. If the indicator readings vary, proceed as follows to find the actual angle of taper: 1) Adjust the angle of the sine-bar until the indicator reading is constant. Then find the new angle B ′ as explained in the paragraph Measuring Angle of Templet or Gage with Sine-Bar on page 694; and Using the angle B ′ calculate the actual half-angle A ′ /2 of the taper from the formula: tan csc cos sin A D B B 2 2 = + l l l The taper per foot corresponding to certain half-angles of taper may be found in the table on page 698. Dimensioning Tapers.— At least three methods of dimensioning tapers are in use. Standard Tapers: Give one diameter or width, the length, and insert note on drawing designating the taper by number. Special Tapers: In dimensioning a taper when the slope is specified, the length and only one diameter should be given or the diameters at both ends of the taper should be given and length omitted. Precision Work: In certain cases where very precise measurements are necessary, the taper surface, either external or internal, is specified by giving a diameter at a certain dis tance from a surface and the slope of the taper.
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