Machinery's Handbook, 31st Edition
Clearance Holes
1743
Table 3a. Standard Metric Drills For Inch Fasteners ANSI/ASME B18.2.8-1999 (R2017)
Nominal Drill Size, mm
Nominal Drill Size, mm
Nominal Screw Size, inch
Nominal Screw Size, inch
Fit Classes
Fit Classes
Normal
Close
Loose
Normal
Close
Loose
10.2 11.8 14.25 17.5 20.5
9.9 11.5 13.5
10.5 12.2 15.5
#0 #1 #2 #3 #4 #5 #6 #8
1.9 2.25 2.6 2.9 3.3
1.7 2.05 2.4 2.7
2.4 2.6 2.9 3.3 3.7 4.4 4.7 5.4 7.5 9.1 6
3 ∕ 8
7 ∕ 16
1 ∕ 2 5 ∕ 8 3 ∕ 4 7 ∕ 8
16.75
19 23 26
20 23 26
3
24
4
3.6 3.9 4.6 5.2 6.7 8.3
4.3
1
27.5
29.5 33.5 36.5
31 34 38 41
29.5 32.5 36.5 39.5
5
1 1 ∕ 8 1 1 ∕ 4 1 3 ∕ 8 1 1 ∕ 2
#10
5.6 7.1 8.7
41 44
1 ∕ 4
5 ∕ 16
Table 3b. Standard Inch Drills For Metric Fasteners ANSI/ASME B18.2.8-1999 (R2017)
Nominal Drill Size, inch
Nominal Drill Size, inch
Nominal Screw Size, mm
Nominal Screw Size, mm
Fit Classes
Fit Classes
Normal
Close
Loose
Normal
Close 43 ∕ 64 53 ∕ 64 63 ∕ 64 1 7 ∕ 32 1 15 ∕ 32 1 11 ∕ 16 1 31 ∕ 32 2 5 ∕ 16
Loose 47 ∕ 64 15 ∕ 16 1 7 ∕ 64 1 3 ∕ 8 1 21 ∕ 32 1 29 ∕ 32 2 3 ∕ 16
M1.6
#50 3 ∕ 32 #33 #29 #16 7 ∕ 32
#51 #44 #36
#47 #38 #31 9 ∕ 64 #12 25 ∕ 64 31 ∕ 64 37 ∕ 64 21 ∕ 32 #1 J
M16 M20 M24 M30 M36 M42 M48 M56 M64 M72
11 ∕ 16 55 ∕ 64 1 1 ∕ 32 1 9 ∕ 32 1 17 ∕ 32 1 25 ∕ 32 2 1 ∕ 32 2 7 ∕ 16
M2
M2.5
M3 M4 M5 M6
1 ∕ 8
#19
#4 1 ∕ 4 Q
G T
M8 M10 M12 M14
2 5 ∕ 8
Z
2 5 ∕ 8
2 15 ∕ 16
2 3 ∕ 4 3 1 ∕ 8
7 ∕ 16
2 15 ∕ 16
3 1 ∕ 4
17 ∕ 32 39 ∕ 64
33 ∕ 64 19 ∕ 32
… … … …
Table 4. Recommended Clearance Holes for Metric Round Head Square Neck Bolts R h H Close Clearance: Close clearance should be specified only for square holes in very thin and/or soft material, or for slots, or where conditions such as critical alignment of assembled parts, wall thickness, or other limitations necessitate use of a minimal hole. Allowable swell or fins on the bolt body and/or fins on the corners of the square neck may interfere with close clearance round or square holes.
Normal Clearance: Normal clearance hole sizes are preferred for general purpose applications and should be specified unless special design considerations dictate the need for either a close or loose clearance hole.
Clearance Normal
Clearance Normal
Nom. Bolt Dia., D and Thd. Pitch
Nom. Bolt Dia., D and Thd. Pitch
Close
Loose
Close
Loose
Corner Radius R h
Corner Radius R h
Min. Hole Diameter or Square Width, H
Min. Hole Diameter or Square Width, H
5.5 6.6
… 5.8 … 7.0
0.2 0.3 0.4 0.4 0.6
15.0 17.0 21.0 25.0
15.5 17.5 22.0 26.0
16.5 18.5 24.0 28.0
0.6 0.6 0.8 1.0
M5 × 0.8 M6 × 1 M8 × 1.25 M10 × 1.5
M14 × 2 M16 × 2 M20 × 2.5 M24 × 3
… 9.0 … 11.0
10.0 12.0 14.5
M12 × 1.75 … … … … … Loose Clearance: Loose clearance hole sizes should be specified only for applications where maximum adjustment capability between components being assembled is necessary. Loose clearance square hole or slots may not prevent bolt turning during wrenching. All dimensions are in millimeters. Source: ANSI/ASME B18.5.2.2M-1982, Appendix II 13.0 13.5
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