ASME B18.6.3 Close Tolerance 100 Degree Flat Countersunk Head
Machine Screws Standard is intended to cover the complete general and dimensional data for the
various types of slotted and recessed head machine screws, tapping screws, and metallic drive screws
recognized as American National Standard. Also included are appendices that provide specifications and
instructions for the protrusion gaging of flat countersunk head screws; across-corners gaging of hex head
screws; penetration gaging and wobble gaging of recessed head screws; approximate hole size for tapping
screws; wrench openings for hex and square products; thread dimensions for the No. 0000, No. 000, and No.
00 sizes; means for determining effective grip lengths on screws; documentation for screw types and head
types relegated to not-recommended or limited-usage status; and formulas on which dimensional data are
based. It shall be understood, however, that where questions arise concerning acceptance of product, the
dimensions in the tables shall govern over recalculation by formula.
The inclusion of dimensional data in ASME B18.6.3 Standard is not intended to imply that
all of the products
described are stock production sizes. Consumers should consult with suppliers concerning the availability
of products.
| Nominal Size | Head Diameter, A | Head Height, H | Slot Width, J | Slot Depth, T | Protrusion Above Gaging Diameter, F | Gaging Diameter, G | |||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Max. | Min. | Ref. | Max. | Min. | Max. | Min. | Max. | Min. | |||
| 4 | 2.845 | 5.385 | 4.775 | 1.245 | 0.991 | 0.787 | 0.610 | 0.432 | 0.635 | 0.483 | 4.242 |
| 6 | 3.505 | 6.655 | 5.969 | 1.524 | 1.219 | 0.991 | 0.762 | 0.559 | 0.711 | 0.533 | 5.436 |
| 8 | 4.166 | 7.925 | 7.163 | 1.829 | 1.372 | 1.143 | 0.914 | 0.686 | 0.787 | 0.584 | 6.629 |
| 10 | 4.826 | 9.195 | 8.357 | 2.108 | 1.524 | 1.270 | 1.067 | 0.787 | 0.864 | 0.660 | 7.798 |
| 1/4 | 6.350 | 12.116 | 11.100 | 2.794 | 1.905 | 1.626 | 1.397 | 1.067 | 1.016 | 0.787 | 10.541 |
| 5/16 | 7.938 | 15.164 | 13.970 | 3.505 | 2.134 | 1.829 | 1.753 | 1.346 | 1.194 | 0.940 | 13.360 |
| 3/8 | 9.525 | 18.212 | 16.815 | 4.191 | 2.388 | 2.057 | 2.108 | 1.651 | 1.346 | 1.067 | 16.205 |
| 7/16 | 11.113 | 21.260 | 19.660 | 4.902 | 2.388 | 2.057 | 2.464 | 1.930 | 1.524 | 1.194 | 19.050 |
| 1/2 | 12.700 | 24.308 | 22.530 | 5.613 | 2.692 | 2.311 | 2.819 | 2.235 | 1.676 | 1.346 | 21.895 |
| 9/16 | 14.288 | 27.356 | 25.400 | 6.325 | 2.997 | 2.591 | 3.175 | 2.515 | 1.854 | 1.473 | 24.740 |
| 5/8 | 15.875 | 30.404 | 28.245 | 7.010 | 3.378 | 2.946 | 3.531 | 2.819 | 2.032 | 1.600 | 27.584 |
| Nominal Size | Head Diameter, A | Head Height, H | Slot Width, J | Slot Depth, T | Protrusion Above Gaging Diameter, F | Gaging Diameter, G | |||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Max. | Min. | Ref. | Max. | Min. | Max. | Min. | Max. | Min. | |||
| 4 | 0.1120 | 0.212 | 0.188 | 0.049 | 0.039 | 0.031 | 0.024 | 0.017 | 0.025 | 0.019 | 0.167 |
| 6 | 0.1380 | 0.262 | 0.235 | 0.060 | 0.048 | 0.039 | 0.030 | 0.022 | 0.028 | 0.021 | 0.214 |
| 8 | 0.1640 | 0.312 | 0.282 | 0.072 | 0.054 | 0.045 | 0.036 | 0.027 | 0.031 | 0.023 | 0.261 |
| 10 | 0.1900 | 0.362 | 0.329 | 0.083 | 0.060 | 0.050 | 0.042 | 0.031 | 0.034 | 0.026 | 0.307 |
| 1/4 | 0.2500 | 0.477 | 0.437 | 0.110 | 0.075 | 0.064 | 0.055 | 0.042 | 0.040 | 0.031 | 0.415 |
| 5/16 | 0.3125 | 0.597 | 0.550 | 0.138 | 0.084 | 0.072 | 0.069 | 0.053 | 0.047 | 0.037 | 0.526 |
| 3/8 | 0.3750 | 0.717 | 0.662 | 0.165 | 0.094 | 0.081 | 0.083 | 0.065 | 0.053 | 0.042 | 0.638 |
| 7/16 | 0.4375 | 0.837 | 0.774 | 0.193 | 0.094 | 0.081 | 0.097 | 0.076 | 0.060 | 0.047 | 0.750 |
| 1/2 | 0.5000 | 0.957 | 0.887 | 0.221 | 0.106 | 0.091 | 0.111 | 0.088 | 0.066 | 0.053 | 0.862 |
| 9/16 | 0.5625 | 1.077 | 1.000 | 0.249 | 0.118 | 0.102 | 0.125 | 0.099 | 0.073 | 0.058 | 0.974 |
| 5/8 | 0.6250 | 1.197 | 1.112 | 0.276 | 0.133 | 0.116 | 0.139 | 0.111 | 0.080 | 0.063 | 1.086 |
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