Metric Self-Threading Screws Machinery's Handbook, 31st Edition
1853
Table 5. Clearance Holes for Metric Tapping Screws ANSI/ASME B18.6.5M-2000 (Withdrawn), Appendix
Basic Clearance Hole Diameter a
Basic Clearance Hole Diameter a
Nominal Screw Size and Thread Pitch
Nominal Screw Size and Thread Pitch
Normal Clearance (Preferred) b
Normal Clearance (Preferred) b
Close Clearance b
Loose Clearance b
Close Clearance b
Loose Clearance b
Types AB, B, BF, and BT
Types D, F, and T
2.40 3.10 3.70 4.50 5.10 5.90 6.70 8.40
2.60 3.30 3.90 4.70 5.30 6.10 6.90 9.00
2.80 3.50 4.20 5.00 5.60 6.50 7.30 10.00
2.20 2.70 3.20 3.70 4.30 5.30 6.40 8.40
2.40 2.90 3.40 3.90 4.50 5.50 6.60 9.00
2.60 3.10 3.60 4.20 4.80 5.80 7.00 10.00
2.2 × 0.8 2.9 × 1 3.5 × 1.3 4.2 × 1.4 4.8 × 1.6 5.5 × 1.8 6.3 × 1.8 8 × 2.1
2 × 0.4 2.5 × 0.45 3 × 0.5 3.5 × 0.6 4 × 0.7 5 × 0.8 6 × 1 8 × 1.25
9.5 × 2.1 12.00 a The values given in this table are minimum limits. The recommended plus tolerances are as follows: for clearance hole diameters over 1.70 to and including 5.80 mm, plus 0.12, 0.20, and 0.30 mm for close, normal, and loose clearances, respectively; over 5.80 to and including 14.50 mm, plus 0.18, 0.30, and 0.45 mm for close, normal, and loose clearances, respectively. 10.00 10.50 11.50 10 × 1.5 10.50 11.00 b Normal clearance hole sizes are preferred. Close clearance hole sizes are for situations such as critical alignment of assembled components, wall thickness, or other limitations that necessitate the use of a minimal hole. Countersinking or counterboring at the fastener entry side may be necessary for the proper seating of the head. Loose clearance hole sizes are for applications where maximum adjustment capability between the components being assembled is necessary. All dimensions are in millimeters. Approximate Installation Hole Sizes for Metric Tapping Screws.— The approximate hole sizes given in Table 7 through Table 9 provide general guidance in selecting holes for installing the respective types of metric thread forming and thread cutting tapping screws in various commonly used materials. Types AB, B, BF, and BT metric tapping screws are covered in these tables; hole sizes for Types D, F, and T metric thread cutting tapping screws are still under development.
Table 6. Approximate Pierced or Extruded Hole Sizes for Steel Types AB and B Metric Thread Forming Tapping Screws
Nominal Screw Size and Thread Pitch
Nominal Screw Size and Thread Pitch
Nominal Screw Size and Thread Pitch
Metal Thickness
Hole Size 2.18 2.18 2.49 2.49 2.49 2.82 2.82 2.82 2.82 2.82 2.18 2.18 2.18 2.18 2.82 2.82
Metal Thickness
Hole Size 3.45 3.45 3.45 3.45 3.45 3.99 3.99 3.99 3.99 3.99 2.82 2.82 3.45 3.45 3.45 3.45
Metal Thickness
Hole Size 4.70 4.70 4.70 4.70 5.31 5.31 5.31
In Steel, Stainless Steel, Monel, and Brass Sheet Metal
0.38 0.46 0.61 0.76 0.91 0.38 0.46 0.61 0.76 0.91 0.61 0.76 0.91 1.22 0.61 0.76
0.46 0.61 0.76 0.91 1.22 0.46 0.61 0.76 0.91 1.22 0.91 1.22 0.61 0.76 0.91 1.22
0.61 0.76 0.91 1.22 0.76 0.91 1.22
2.9 × 1
4.2 × 1.4
5.5 × 1.8
… …
3.5 × 1.3
4.8 × 1.6
6.3 × 1.8
… … … …
In Aluminum Alloy
0.61 0.76 0.91 1.22
3.99 3.99 3.99 3.99
3.5
× 1.3
2.9 × 1
4.8 × 1.6
4.2 × 1.4
… … … …
3.5 × 1.3
All dimensions are in millimeters.
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