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MIKI PULLEY Coupling Standard Hole Drilling Standards

Last updated:18 June 2019

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These standard hole drilling standards apply to the 6 mm to 65 mm hole drilling for SERVOFLEX (excluding SFC), SPRFLEX, BAUMANNFLEX (excluding ZG and LM), and CENTAFLEX. However, if other standard hole drilling standards are available for each model, those standards are given priority and may not match these standards.

Hole Drilling Tolerances for the Mating Shaft Tolerances

Unless otherwise specified, a hole is drilled with a tolerance of H7. However, H8 is used for holes with a diameter of 10 mm or less. The following shows the recommended hole tolerances for the shaft tolerances. With the exception of H7, the tolerance must be determined through discussion. Surface finishing is not performed for the additional drilled hole based on the prepared hole. If surface finishing is required for the additional drilled hole, please contact Miki Pulley.

Shaft tolerance Recommended hole tolerance
h6~h9 H7
j6 G7
k6 F7
m6 F7
* j6, k6, and m6 are used for new standard motor shafts.

Keyway Sizes for Hole Diameters (Table Below)

Unless otherwise specified, a hole is drilled according to the old JIS (class 2) standards. Keyway is not made for holes of less than 12 mm.

Old JIS (Class 2) Standards Unit [mm]

Hole diameter b2 t2 Key size b×h
Standard size Tolerance(E9) Standard size Tolerance
12 or more and 13 or below 4 +0.050 +0.020 1.5 +0.3 0 4×4
Over 13 and 20 or below 5 2.0 5×5
Over 20 and 30 or below 7 +0.061 +0.025 3.0 +0.3 0 7×7
Over 30 and 40 or below 10 3.5 10×8
Over 40 and 50 or below 12 +0.075 +0.032 12×8
Over 50 and 60 or below 15 5.0 15×10
Over 60 and 65 or below 18 6.0 18×12

New JIS Standards Unit [mm]

Hole diameter b2 t2 Key size b×h
Standard size Tolerance(H9) Standard size Tolerance
12 4 +0.030
0		 1.8 +0.3
0		 4×4
Over 12 and 17 or belo 5 2.3 5×5
Over 17 and 22 or below 6 2.8 6×6
Over 22 and 30 or below 8 +0.036
0		 3.3 +0.3
0		 8×7
Over 30 and 38 or below 10 10×8
Over 38 and 44 or below 12 +0.043
0		 12×8
Over 44 and 50 or below 14 3.8 14×9
Over 50 and 58 or below 16 4.3 16×10
Over 58 and 65 or below 18 4.4 18×11

Nominal Set Screw Diameters for Keyways

Keyway standard size b2 Nominal set screw diameter
4 M4
5 M4
6 M5
7 M6
8 M6
10 M8
12 M8
14 M10
15 M10
16 M10
18 M10
* Unless otherwise specified, the set screw position is 90° at two points.
* The set screw position varies depending on the applied product. For details, refer to the standard hole drilling standards of each product.

Nominal Set Screw Diameter for Hole Diameter (without Keyway)

Hole diameter Nominal set screw diameter
6 or more and under 12 M4
* Unless otherwise specified, the set screw position is 90° at two points.
* The set screw position varies depending on the applied product. For details, refer to the standard hole drilling standards of each product.

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