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Letter Sizes Series J100
General purpose drills for steels, cast steel, grey cast iron, malleable cast iron, nickel brass, aluminium alloy and graphite. Point angle: 118, helix angle: normal, web thickness: standard, relief angle: 8 - 20, tolerance of diameter: h8, tolerance of shank: f11. Manufactured to ANSI B328, BS 328 and DIN 338.
Number & Letter Gauge Drills
Gauge drills are still in common use in the U.S. In the past, they were popular elsewhere, but now have been largely discarded in favour of metric sizes. When using a gauge rather than a standard measurement of size the user has to refer to a table of gauge sizes. For example, to drill a hole which is 10 thou (thousandth of an inch = .0010) bigger than a 1/8 inch bolt, the user must first work out that 1/8 inch is
125 thou, so the hole size needed is 135 thou, and then must look up in a reference book which gauge drill bit is closest to this diameter - a number 29.
Number gauge sizes are similar or equivalent in some respects to, but different from, American wire gauge.
Number gauge is usually used from size 80 (the smallest) to size 1 (the largest) followed by letter gauge size A (the smallest) to size Z (the largest). Number gauge is actually defined down to size 97, but these smaller sizes are rarely encountered. It happens that as the technology for making small drill bits and drilling small holes has become more available,
metric drills have become the norm.
The gauge-to-diameter conversion does not follow a set formula, but rather was defined as a useful and practical measure. The graph shows how gauge diameters change with gauge. Each step along the horizontal axis is one gauge size.
The step size between adjacent gauges is smaller for smaller gauges. This is appropriate, because the tolerance of the diameter of drilled holes is closer for smaller drill bits.
Gaugeinch mm
800.0140.343
790.0150.368
780.0160.406
770.0180.457
760.0200.508
750.0210.533
740.0230.572
730.0240.610
720.0250.635
710.0260.660
700.0280.711
690.0290.742
680.0310.787
670.0320.813
660.0330.838
650.0350.889
640.0360.914
630.0370.940
620.0380.965
610.0390.991
600.0401.016
590.0411.041
580.0421.067
570.0431.092
560.0461.181
550.0521.321
540.0551.397
530.0591.511
520.0641.613
510.0671.702
500.0701.778
490.0731.854
480.0761.930
470.0791.994
460.0812.057
450.0822.083
440.0862.184
430.0892.261
420.0942.375
410.0962.438
400.0982.489
390.0992.527
380.1012.578
370.1042.642
360.1062.705
350.1102.794
340.1112.819
330.1132.870
320.1162.946
310.1203.048
300.1293.264
290.1363.454
280.1413.569
270.1443.658
260.1473.734
250.1493.797
240.1523.861
230.1543.912
220.1573.988
210.1594.039
200.1614.089
190.1664.216
180.1694.305
170.1734.394
160.1774.496
150.1804.572
140.1824.623
130.1854.699
120.1894.801
110.1914.851
100.1944.915
90.1964.978
80.1995.055
70.2015.105
60.2045.182
50.2065.220
40.2095.309
30.2135.410
20.2215.613
10.2285.791
A0.2345.944
B0.2386.045
C0.2426.147
D0.2466.248
E0.2506.350
F0.2576.528
G0.2616.629
H0.2666.756
I0.2726.909
J0.2777.036
K0.2817.137
L0.2907.366
M0.2957.493
N0.3027.671
O0.3168.026
P0.3238.204
Q0.3328.433
R0.3398.611
S0.3488.839
T0.3589.093
U0.3689.347
V0.3779.576
W0.3869.804
X0.39710.08
Y0.40410.26
Z0.41310.49
Finish/Coating | Black Oxide |
Standards Met | ANSI B328 | BS 328 | DIN 338 |
Helix Type | Normal Helix |
Trade Letter | X |
Shank Diameter Tolerance | F11 |
Web Thickness | Standard |
Material | HSS |
Coolant Delivery | External |
Flute Type | Spiral |
Drill Diameter Letter | X |
Point Angle | 118\u00b0 |
Gauge Size | X |
Drill Diameter Tolerance | H8 |
Flute Length | 87mm |
Overall Length | 133mm |
Flute Construction | Ground flutes |
Series | J100 |
Number of Flutes | 2 |
Point Type | Split Point |
Cutting Direction | Right Hand |
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