# Sheet metal screw pilot holes: drill size and hole diameter for Types AB, A and 1/23/F, by sheet thickness (#2 to 1/2)

> What drill size and hole diameter does a #8 sheet metal screw need in 18 gauge or 0.036 in steel?

- Category: Hardware › Fasteners
- Kind: Standard part
- Basis: AFT Fasteners' self-tapping screw hole-size tables (test-plate gage and thickness, drill, hole diameter) and Engineers Edge's Type A table by metal thickness (pierced / extruded versus drilled / clean punched); numbers only
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**Exact dimensions.** Every file is drawn at true size with no tolerance added. The holes and pins that meet another part are listed below under Mating features, with the fit each joint needs; open those by your process's clearance before making the part.

## Notes

- Inch tables. AFT gives, per screw size and thread (size-TPI), the test-plate gage and its thickness max / min, the drill size (number, letter, fraction or mm as printed) and the resulting hole diameter, for Types AB / B / 25 (thread forming), Type A (spaced thread, no plate thickness given) and Types 1 / 23 / F (thread cutting). Engineers Edge gives Type A holes by metal thickness: the hole diameter for pierced or extruded holes and for drilled or clean-punched holes, with the drill size, for #4 to #14 in steel, stainless steel, Monel, brass and aluminum. AFT states holes can be drilled, core drilled, punched, pierced or extruded and that burrs should be removed if they interfere; hole size is the nominal hole diameter, not a tolerance. Engineers Edge prints no units; the values read as inches.
- Oddities kept as printed, not corrected: AFT's Types AB row '4.24' (printed with a dot; the thread is 4-24); the 8-18 row gives gage 14 with thickness .1270 / .1230 in (1/8 in), unlike the gage 14 rows above it (.0770 / .0730 in); the 3-48 row of the thread-cutting table prints .0920 for both max and min. AFT's Type A table lists sizes 5 to 24 (24-9 for the 11/32 in drill) with threads different from the AB table (for example 6-18 versus 6-20), because the type has a different thread.
- Not on this page: pilot holes for plastics and wood (see plastic-thread-forming-screw-holes and wood-screws-flat-head-inch), the AFT Type U drive-screw and High-Low tables (read but not tabulated), and metric ST sizes (the sources read give no hole table for them). The two sources do not overlap in the same screw type and thickness for every size: for example #8 Type A is 0.136 in (drill #29) in AFT's Type A table, Engineers Edge prints 0.125 in (1/8 in drill) for drilled holes in 0.018 to 0.036 in steel and 0.136 in for pierced holes, so check the table for your thickness.
- No file: these are hole sizes (numbers). McMaster-Carr sells sheet metal screws with per-part STEP; its category is linked on self-tapping-screws-iso-7049-pan-head.

## Mating features (exact size; open press / slide / run / socket by your process clearance, leave designed and clamp as drawn)

| feature | exact | mates with | fit | files |
|---|---|---|---|---|
| pilot hole | Type AB: 8-18 drill 29 (.1360 in), 10-16 drill 21 (.1590 in), 1/4-14 drill 5.5 mm (.2165 in); Type A by thickness in the table | Type AB, A or 1 / 23 / F screw of the listed size | designed | all |

## Sizes

| source / screw type | size (size-TPI, or # for Engineers Edge) | test plate or metal thickness | drill size | hole diameter, drilled / clean punched (in) | hole diameter, pierced or extruded (in) |
|---|---|---|---|---|---|
| AFT, Types AB / B / 25 | 2-32 | gage 18, .0500 / .0460 in | 48 | .0760 | — |
| AFT, Types AB / B / 25 | 3-28 | gage 18, .0500 / .0460 in | 46 | .0810 | — |
| AFT, Types AB / B / 25 | 4-24 (printed 4.24) | gage 18, .0500 / .0460 in | 44 | .0860 | — |
| AFT, Types AB / B / 25 | 5-20 | gage 18, .0500 / .0460 in | 36 | .1065 | — |
| AFT, Types AB / B / 25 | 6-20 | gage 14, .0770 / .0730 in | 32 | .1160 | — |
| AFT, Types AB / B / 25 | 7-19 | gage 14, .0770 / .0730 in | 30 | .1285 | — |
| AFT, Types AB / B / 25 | 8-18 | gage 14, .1270 / .1230 in | 29 | .1360 | — |
| AFT, Types AB / B / 25 | 10-16 | gage 1/8, .1270 / .1230 in | 21 | .1590 | — |
| AFT, Types AB / B / 25 | 12-14 | gage 1/8, .1270 / .1230 in | 3/16 | .1875 | — |
| AFT, Types AB / B / 25 | 1/4-14 | gage 3/16, .1905 / .1845 in | 5.5 mm | .2165 | — |
| AFT, Types AB / B / 25 | 5/16-12 | gage 3/16, .1905 / .1845 in | I | .2720 | — |
| AFT, Types AB / B / 25 | 3/8-12 | gage 3/16, .1905 / .1845 in | 21/64 | .3281 | — |
| AFT, Type A | 5-20 | — | #36 | 0.1065 | — |
| AFT, Type A | 6-18 | — | #32 | 0.1160 | — |
| AFT, Type A | 7-16 | — | #30 | 0.1285 | — |
| AFT, Type A | 8-15 | — | #29 | 0.1360 | — |
| AFT, Type A | 9-14 | — | #26 | 0.1470 | — |
| AFT, Type A | 10-12 | — | #21 | 0.1590 | — |
| AFT, Type A | 12-11 | — | 3/16 | 0.1875 | — |
| AFT, Type A | 14-10 | — | 5.5 mm | 0.2165 | — |
| AFT, Type A | 20-9 | — | L | 0.2900 | — |
| AFT, Type A | 24-9 | — | 11/32 | 0.3438 | — |
| AFT, Types 1 / 23 / F (thread cutting) | 2-56 | gage 18, .0800 / .0760 in | 49 | 0.0730 | — |
| AFT, Types 1 / 23 / F (thread cutting) | 3-48 | gage 18, .0920 / .0920 in | 46 | 0.0810 | — |
| AFT, Types 1 / 23 / F (thread cutting) | 4-40 | gage 18, .1110 / .1070 in | 41 | 0.0960 | — |
| AFT, Types 1 / 23 / F (thread cutting) | 5-40 | gage 18, .1110 / .1070 in | 37 | 0.1010 | — |
| AFT, Types 1 / 23 / F (thread cutting) | 6-32 | gage 14, .1425 / .1385 in | 31 | 0.1200 | — |
| AFT, Types 1 / 23 / F (thread cutting) | 8-32 | gage 14, .1905 / .1845 in | 26 | 0.1470 | — |
| AFT, Types 1 / 23 / F (thread cutting) | 10-24 | gage 1/8, .1905 / .1845 in | 17 | 0.1730 | — |
| AFT, Types 1 / 23 / F (thread cutting) | 10-32 | gage 1/8, .1905 / .1845 in | 16 | 0.1770 | — |
| AFT, Types 1 / 23 / F (thread cutting) | 12-24 | gage 1/8, .1905 / .1845 in | 8 | 0.1990 | — |
| AFT, Types 1 / 23 / F (thread cutting) | 1/4-20 | gage 3/16, .2530 / .2470 in | 1 | 0.2280 | — |
| AFT, Types 1 / 23 / F (thread cutting) | 5/16-18 | gage 3/16, .3155 / .3095 in | L | 0.2900 | — |
| AFT, Types 1 / 23 / F (thread cutting) | 3/8-16 | gage 3/16, .3780 / .3720 in | T | 0.3580 | — |
| AFT, Types 1 / 23 / F (thread cutting) | 1/2-13 | gage 3/16, .471 / .443 in | 29/64 | 0.4531 | — |
| Engineers Edge, Type A by metal thickness | #4 | 0.015 in | 44 | 0.086 | — |
| Engineers Edge, Type A by metal thickness | #4 | 0.018 in | 44 | 0.086 | — |
| Engineers Edge, Type A by metal thickness | #4 | 0.024 in | 42 | 0.094 | 0.098 |
| Engineers Edge, Type A by metal thickness | #4 | 0.030 in | 42 | 0.094 | 0.098 |
| Engineers Edge, Type A by metal thickness | #4 | 0.036 in | 40 | 0.098 | 0.098 |
| Engineers Edge, Type A by metal thickness | #6 | 0.015 in | 37 | 0.104 | — |
| Engineers Edge, Type A by metal thickness | #6 | 0.018 in | 37 | 0.104 | — |
| Engineers Edge, Type A by metal thickness | #6 | 0.024 in | 37 | 0.104 | 0.111 |
| Engineers Edge, Type A by metal thickness | #6 | 0.030 in | 37 | 0.104 | 0.111 |
| Engineers Edge, Type A by metal thickness | #6 | 0.036 in | 36 | 0.106 | 0.111 |
| Engineers Edge, Type A by metal thickness | #7 | 0.015 in | 32 | 0.116 | — |
| Engineers Edge, Type A by metal thickness | #7 | 0.018 in | 32 | 0.116 | — |
| Engineers Edge, Type A by metal thickness | #7 | 0.024 in | 32 | 0.116 | 0.120 |
| Engineers Edge, Type A by metal thickness | #7 | 0.030 in | 32 | 0.116 | 0.120 |
| Engineers Edge, Type A by metal thickness | #7 | 0.036 in | 32 | 0.116 | 0.120 |
| Engineers Edge, Type A by metal thickness | #7 | 0.048 in | 31 | 0.120 | 0.120 |
| Engineers Edge, Type A by metal thickness | #8 | 0.018 in | 1/8 | 0.125 | — |
| Engineers Edge, Type A by metal thickness | #8 | 0.024 in | 1/8 | 0.125 | 0.136 |
| Engineers Edge, Type A by metal thickness | #8 | 0.030 in | 1/8 | 0.125 | 0.136 |
| Engineers Edge, Type A by metal thickness | #8 | 0.036 in | 1/8 | 0.125 | 0.136 |
| Engineers Edge, Type A by metal thickness | #8 | 0.048 in | 30 | 0.128 | 0.136 |
| Engineers Edge, Type A by metal thickness | #10 | 0.018 in | 29 | 0.136 | — |
| Engineers Edge, Type A by metal thickness | #10 | 0.024 in | 29 | 0.136 | 0.157 |
| Engineers Edge, Type A by metal thickness | #10 | 0.030 in | 29 | 0.136 | 0.157 |
| Engineers Edge, Type A by metal thickness | #10 | 0.036 in | 29 | 0.136 | 0.157 |
| Engineers Edge, Type A by metal thickness | #10 | 0.048 in | 25 | 0.149 | 0.157 |
| Engineers Edge, Type A by metal thickness | #12 | 0.024 in | 20 | 0.161 | — |
| Engineers Edge, Type A by metal thickness | #12 | 0.030 in | 20 | 0.161 | 0.185 |
| Engineers Edge, Type A by metal thickness | #12 | 0.036 in | 20 | 0.161 | 0.185 |
| Engineers Edge, Type A by metal thickness | #12 | 0.048 in | 20 | 0.161 | 0.185 |
| Engineers Edge, Type A by metal thickness | #14 | 0.024 in | 13 | 0.185 | — |
| Engineers Edge, Type A by metal thickness | #14 | 0.030 in | 12 | 0.189 | 0.209 |
| Engineers Edge, Type A by metal thickness | #14 | 0.036 in | 11 | 0.191 | 0.209 |
| Engineers Edge, Type A by metal thickness | #14 | 0.048 in | 9 | 0.196 | 0.209 |

## Where the files are

- AFT Fasteners: [Self-tapping screws hole size data, Types AB / B / 25, A, 1 / 23 / F, U and High-Low: test-plate gauge and thickness, drill size, hole diameter](https://www.aftfasteners.com/self-tapping-screws-hole-size-data-for-types-a-ab-b-25-1-23-f-u-high-low-technical-information) — web — Publisher's page; dimensions are facts
- Engineers Edge: [Pilot hole sizes for Type A steel sheet metal screws by metal thickness: pierced or extruded versus drilled or clean punched, drill size, #4 to #14](https://engineersedge.com/hardware/pilot_hole_sizes_for_steel_sheet_metal_15670.htm) — web — Publisher's page; dimensions are facts

## Questions

**What drill for a #8 sheet metal screw in 0.030 in steel?**

Engineers Edge (Type A): 1/8 in drill, 0.125 in hole for a drilled or clean-punched hole, 0.136 in for a pierced or extruded hole. AFT's Type A table prints 0.136 in (drill #29) without a thickness.

**What hole for a #10 Type AB screw?**

AFT: size 10-16, drill 21, hole 0.1590 in, in a 1/8 in test plate (0.1270 / 0.1230 in).

**What drill for a 1/4-20 thread-cutting screw?**

AFT Types 1 / 23 / F: drill 1 (0.2280 in) in a 3/16 in test plate.

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