SAE J78 Hex Washer Head Self-drilling Screws
SAE J78 is the leading standard of self-drilling screws in inch system. This standard defines dimensions, tolerance, drill performance of hexagon washer head self-drilling screws.ASME B18.6.4 Hex Washer Head Tapping Screws Head Dimension Reference
| Size |
Width Across Flats |
Width Across Cornors |
Head Height |
Wash Dia. |
Washer Thickness |
| #6 | 0.244-0.250 | >0.272 | 0.080-0.093 | 0.302-0.328 | 0.015-0.025 |
| #8 | 0.244-0.250 | >0.272 | 0.096-0.110 | 0.322-0.348 | 0.019-0.031 |
| #10 | 0.305-0.312 | >0.340 | 0.105-0.120 | 0.384-0.414 | 0.019-0.031 |
| #12 | 0.305-0.312 | >0.340 | 0.139-0.155 | 0.398-0.432 | 0.022-0.039 |
| #14 | 0.367-0.375 | >0.409 | 0.172-0.190 | 0.480-0.520 | 0.030-0.050 |
SAE J78 Type BSD thread ( same to ASME B18.6.4 Self-tapping Thread Type AB)
| Size | Threads Per Inch | Major Dia. | Minor Dia. |
Protrusion Allowance (ref) point#2 |
Protrusion Allowance (ref) point#3 |
| #6 | 20 | 0.132-0.139 | 0.099-0.104 | 0.190 | 0.220 |
| #8 | 18 | 0.159-0.166 | 0.116-0.122 | 0.211 | 0.251 |
| #10 | 16 | 0.182-0.189 | 0.135-0.141 | 0.235 | 0.300 |
| #12 | 14 | 0.208-0.215 | 0.157-0.164 | 0.283 | 0.353 |
| #14 | 14 | 0.237-0.246 | 0.185-0.192 | 0.318 | 0.393 |
SAE J78 Drill-Drive Test Performance Requirement
| Size | Test Plate Thickness,in | Loading C*, lb | Time to drill, second |
| #6 | 0.062-0.068 | 45 | <2.5 |
| #8 | 0.062-0.068 | 45 | <3.0 |
| #10 | 0.062-0.068 | 50 | <3.5 |
| #12 | 0.062-0.068 | 60 | <4.0 |
| #14 | 0.062-0.068 | 60 | <5.0 |
C*: Axial loads tabulated shall apply to chromium finish.
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Self drilling Screws Selection Guide
| Size | Point Style | Recommended Panel Thickness, in. |
| #6 | 2 | 0.080 Max |
| 3 | 0.090-0.110 | |
| #8 | 2 | 0.090 Max |
| 3 | 0.100-0.140 | |
| #10 | 2 | 0.100 Max |
| 3 | 0.110-0.175 | |
| #12 | 2 | 0.140 Max |
| 3 | 0.110-0.210 | |
| 1/4 | 2 | 0.175 Max |
| 3 | 0.110-0.210 |
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Heat treatment
Surface Hardness 50 - 56 HRC (HV520-610), if gas carbonitriding 48-58 HRC (HV490-670)
Core Hardness 32-40HRC (HV320-400).
Case Depth:
#4~#6: 0.002"-0.007"
#8~#12:0.004"-0.009"
>1/4: 0.005"-0.011"