Machinery's Handbook, 31st Edition
958
Twist Drills Table 12. British Standard Morse Taper-Shank Twist Drills and Core Drills — Standard Metric Sizes BS 328: Part 1:1959 Table 12. (Continued) British Standard Morse Taper-Shank Twist Drills
Flute Length
Overall Length
Flute Length
Overall Length
Flute Length
Overall Length
Diameter
Diameter
Diameter
61.00 62.00 63.00 64.00 65.00 66.00 67.00 68.00 69.00 70.00 71.00 72.00 73.00 74.00 75.00
76.00 77.00 78.00 79.00 80.00 81.00 82.00 83.00 84.00 85.00 86.00 87.00 88.00 89.00
260
477
91.00 92.00 93.00 94.00 95.00 96.00 97.00 98.00 99.00 100.00
240
427
275
529
260
514
245
432
265
519
280
534
250
437
250
437
270
524
255
442
90.00 All dimensions are in millimeters. Tolerances on diameters are given in the table below. Table 13 shows twist drills that may be supplied with the shank and length oversize, but they should be regarded as nonpreferred. The Morse taper shanks of these twist and core drills are as follows: 3.00 to 14.00 mm diameter, M.T. No. 1; 14.25 to 23.00 mm diameter, M.T. No. 2; 23.25 to 31.50 mm diameter, M.T. No. 3; 31.75 to 50.50 mm diameter, M.T. No. 4; 51.00 to 76.00 mm diameter, M.T. No. 5; 77.00 to 100.00 mm diameter, M.T. No. 6.
Table 13. British Standard Morse Taper-Shank Twist Drills — Metric Oversize Shank and Length Series BS 328: Part 1:1959
Dia. Range
Overall Length
M. T. No.
Dia. Range
Overall Length
M. T. No.
Dia. Range
Overall Length
M. T. No.
12.00 to 13.20 13.50 to 14.00 18.25 to 19.00 19.25 to 20.00 20.25 to 21.00 21.25 to 22.25
199 206 256 251 266 271
2 2 3 3 3 3
22.50 to 23.00 26.75 to 28.00 29.00 to 30.00 30.25 to 31.50 40.50 to 42.50 43.00 to 45.00
276 319 324 329 392 397
3 4 4 4 5 5
45.50 to 47.50 48.00 to 50.00 64.00 to 67.00 68.00 to 71.00 72.00 to 75.00 50.50
402 407 412 499 504 509
5 5 5 6 6
6 Diameters and lengths are given in millimeters. For the individual sizes within the diameter ranges given, see Table 12. This series of drills should be regarded as non-preferred. Table 14. British Standard Limits of Tolerance on Diameter for Twist Drills and Core Drills — Metric Series BS 328: Part 1:1959 Drill Size (Diameter measured across lands at outer corners) Tolerance (h8) 0 to 1 inclusive Plus 0.000 to Minus 0.014 Over 1 to 3 inclusive Plus 0.000 to Minus 0.014 Over 3 to 6 inclusive Plus 0.000 to Minus 0.018 Over 6 to 10 inclusive Plus 0.000 to Minus 0.022 Over 10 to 18 inclusive Plus 0.000 to Minus 0.027 Over 18 to 30 inclusive Plus 0.000 to Minus 0.033 Over 30 to 50 inclusive Plus 0.000 to Minus 0.039 Over 50 to 80 inclusive Plus 0.000 to Minus 0.046 Over 80 to 120 inclusive Plus 0.000 to Minus 0.054 All dimensions are given in millimeters.
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