Machinery's Handbook, 31st Edition
916
Reamers Straight-Shank Center Reamers and Machine Countersinks ANSI/ASME B94.2-1995 (R2015) D S A S A D Center Reamers (Short Countersinks) Machine Countersinks Dia. of Cut Approx. Length Overall, A Length of Shank, S Dia. of Shank, D Dia. of Cut Approx. Length Overall, A Length of Shank, S
Dia. of Shank, D
1 1 ⁄ 2 1 3 ⁄ 4 2 1 ⁄ 4 2 5 ⁄ 8 2
3 7 ⁄ 8
2 1 ⁄ 4 2 1 ⁄ 4 2 1 ⁄ 4 2 1 ⁄ 4 2 1 ⁄ 4
3 ⁄ 4 7 ⁄ 8
3 ⁄ 16
1 ⁄ 2 5 ⁄ 8 3 ⁄ 4 7 ⁄ 8
1 ⁄ 2 1 ⁄ 2 1 ⁄ 2 1 ⁄ 2
1 ⁄ 4 3 ⁄ 8 1 ⁄ 2 5 ⁄ 8
4
1 ⁄ 4 3 ⁄ 8 3 ⁄ 8 1 ⁄ 2
1 1
4 1 ⁄ 8 4 1 ⁄ 4 4 3 ⁄ 8
1
1 1 ⁄ 4
3 ⁄ 4 1 ⁄ 2 All dimensions are given in inches. Material is high-speed steel. Reamers and countersinks have 3 or 4 flutes. Center reamers are standard with 60, 82, 90, or 100 degrees included angle. Machine countersinks are standard with either 60 or 82 degrees included angle. Tolerances: On overall length A , the tolerance is ± 1 ⁄ 8 inch for center reamers in a size range of from 1 ⁄ 4 to 3 ⁄ 8 inch, incl., and machine countersinks in a size range of from 1 ⁄ 2 to 5 ⁄ 8 inch. incl.; ± 3 ⁄ 16 inch for center reamers, 1 ⁄ 2 to 3 ⁄ 4 inch, incl.; and machine countersinks, 3 ⁄ 4 to 1 inch, incl. On shank diameter D , the tolerance is - 0.0005 to - 0.002 inch. On shank length S , the tolerance is ± 1 ⁄ 16 inch. Calculating Countersink and Spot Drill Depths.— The following formulas are for coun- tersinks and spot drills that have been sharpened to a point, allowances on tool depth will have to be made if the countersink or spot drill is not sharpened to a point.
D
Z
Fig. 1. For Countersinks and Spot Drills that have been Sharpened to a Point α = countersink angle D = countersink diameter Z = depth of tool travel required from surface of part To find the tool travel “Z” required for any sharp-point countersink or spot drill angle, use either of the following formulas: Z = ∙ or Z = ∙ cot D 1 2 tan α 2 D α 2 2 To find the tool travel “ Z - a ” required for any truncated countersink or spot drill angle, use either of the following formulas: Z – a = ∙ D – T 1 2 tan α 2 or Z – a = ∙ D – T 2 cot α 2
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