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Self-tapping (sheet metal) screws: ISO 7049 pan head ST2.2–ST6.3 and ASME B18.6.4 Type AB thread #2 to 3/8
What are the pan head size and thread of a #8 or ST4.2 self-tapping sheet metal screw? · Standard part · basis: fasteners.eu's ISO 7049 table (pan head, form C and F) and two copies of the Type AB thread table (HB Bolt, citing ASME B18.6.4-1998, and a maker sheet citing B18.6.3-2013); numbers only
Also called: iso 7049 dimensions, din 7981 pan head tapping screw, st4.2 screw head diameter, st2.9 screw dimensions, #8 sheet metal screw head size, sheet metal screw thread size chart, type ab screw threads per inch, #10 sheet metal screw major diameter, st3.5 pan head height, self tapping screw size chart, b18.6.4 type ab, st4.8 screw head
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. Mating features
- sizes
- 20 in table
Notes
- ISO 7049 rows are mm, pan head tapping screws with cross recess (types H and Z), forms C (conical point) and F (flat point): thread pitch P, head diameter dk (nominal = max, with min), head height k (nominal = max, with min), r max (under-head radius), rf (head crown radius, 'approx.') and the cross-recess number. ST3.9 is in brackets in the standard (non-preferred), as on the page. The page also tabulates recess depths, the dimension m (approx.) and the minimum / maximum screw length by form, which are not repeated here. Pitch 'a max' equals the pitch in every column. The ST thread itself (ISO 1478) major and minor diameters were not in the source read.
- Type AB rows are inches: nominal size #2 to 3/8, basic screw diameter D, threads per inch, major diameter max / min, minor diameter max / min. HB Bolt cites ASME B18.6.4-1998 and the second sheet cites B18.6.3-2013; the numbers are identical on both. The second sheet labels the two columns after the diameters as 'min practical screw length' for 90° (flat-under-head) and countersunk heads and the last as minimum torsional strength in lb-in for steel screws; HB Bolt's headers were jumbled, so the labels come from that second sheet. Length tolerance (both): ±0.03 in up to 1 in, ±0.05 in over 1 in.
- Pan head dimensions for the inch Type AB / A screws (B18.6.4 pan head tables) were not in the sources read; none is given. The ST-size to Type AB size correspondence (for example ST4.2 versus #8) is not printed by the sources read and is not claimed. Pilot holes for these screws: sheet-metal-screw-pilot-holes; plastics: plastic-thread-forming-screw-holes.
- No file: the pan head crown shape is given by rf 'approx.' and the recess profile is not drawn here, and the thread is a plain cylinder; the brief rule against plain shapes applies. McMaster-Carr sells sheet metal screws with per-part STEP; the category is linked, not copied.
Self-tapping (sheet metal) screws: ISO 7049 pan head ST2.2–ST6.3 and… size chart
| standard | size | pitch / TPI | head dia dk max / min (mm) | head height k max / min (mm) | r max, rf (mm) | major, minor (in) | recess | min practical length (in) | min torsional strength |
|---|---|---|---|---|---|---|---|---|
| ISO 7049 pan head (mm) | ST2.2 | 0.8 mm | 4.2 / 3.9 | 1.8 / 1.55 | r max 0.3; rf ≈ 3.4 | cross recess No. 1 | — | — |
| ISO 7049 pan head (mm) | ST2.9 | 1.1 mm | 5.6 / 5.3 | 2.2 / 1.95 | r max 0.4; rf ≈ 4.4 | cross recess No. 1 | — | — |
| ISO 7049 pan head (mm) | ST3.5 | 1.3 mm | 6.9 / 6.54 | 2.6 / 2.35 | r max 0.5; rf ≈ 5.4 | cross recess No. 2 | — | — |
| ISO 7049 pan head (mm) | (ST3.9) | 1.3 mm | 7.5 / 7.14 | 2.8 / 2.55 | r max 0.5; rf ≈ 5.8 | cross recess No. 2 | — | — |
| ISO 7049 pan head (mm) | ST4.2 | 1.4 mm | 8.2 / 7.84 | 3.05 / 2.75 | r max 0.6; rf ≈ 6.2 | cross recess No. 2 | — | — |
| ISO 7049 pan head (mm) | ST4.8 | 1.6 mm | 9.5 / 9.14 | 3.55 / 3.25 | r max 0.7; rf ≈ 7.2 | cross recess No. 2 | — | — |
| ISO 7049 pan head (mm) | ST5.5 | 1.8 mm | 10.8 / 10.37 | 3.95 / 3.65 | r max 0.8; rf ≈ 8.2 | cross recess No. 3 | — | — |
| ISO 7049 pan head (mm) | ST6.3 | 1.8 mm | 12.5 / 12.07 | 4.55 / 4.25 | r max 0.9; rf ≈ 9.5 | cross recess No. 3 | — | — |
| ASME B18.6.4 Type AB thread (in) | #2 | 32 TPI; basic .0860 | — | — | major .088 / .082; minor .064 / .060 | — | 3/16 (90° heads); 7/32 (csk heads) | 4 lb-in (steel) |
| ASME B18.6.4 Type AB thread (in) | #3 | 28 TPI; basic .0990 | — | — | major .101 / .095; minor .075 / .071 | — | 3/16 (90° heads); 1/4 (csk heads) | 9 lb-in (steel) |
| ASME B18.6.4 Type AB thread (in) | #4 | 24 TPI; basic .1120 | — | — | major .114 / .108; minor .086 / .082 | — | 7/32 (90° heads); 9/32 (csk heads) | 13 lb-in (steel) |
| ASME B18.6.4 Type AB thread (in) | #5 | 20 TPI; basic .1250 | — | — | major .130 / .123; minor .094 / .090 | — | 1/4 (90° heads); 5/16 (csk heads) | 18 lb-in (steel) |
| ASME B18.6.4 Type AB thread (in) | #6 | 20 TPI; basic .1380 | — | — | major .139 / .132; minor .104 / .099 | — | 9/32 (90° heads); 11/32 (csk heads) | 24 lb-in (steel) |
| ASME B18.6.4 Type AB thread (in) | #7 | 19 TPI; basic .1510 | — | — | major .154 / .147; minor .115 / .109 | — | 5/16 (90° heads); 3/8 (csk heads) | 30 lb-in (steel) |
| ASME B18.6.4 Type AB thread (in) | #8 | 18 TPI; basic .1640 | — | — | major .166 / .159; minor .122 / .116 | — | 5/16 (90° heads); 3/8 (csk heads) | 39 lb-in (steel) |
| ASME B18.6.4 Type AB thread (in) | #10 | 16 TPI; basic .1900 | — | — | major .189 / .182; minor .141 / .135 | — | 3/8 (90° heads); 7/16 (csk heads) | 56 lb-in (steel) |
| ASME B18.6.4 Type AB thread (in) | #12 | 14 TPI; basic .2160 | — | — | major .215 / .208; minor .164 / .157 | — | 7/16 (90° heads); 21/32 (csk heads) | 88 lb-in (steel) |
| ASME B18.6.4 Type AB thread (in) | 1/4 | 14 TPI; basic .2500 | — | — | major .246 / .237; minor .192 / .185 | — | 1/2 (90° heads); 19/32 (csk heads) | 142 lb-in (steel) |
| ASME B18.6.4 Type AB thread (in) | 5/16 | 12 TPI; basic .3125 | — | — | major .315 / .306; minor .244 / .236 | — | 5/8 (90° heads); 3/4 (csk heads) | 290 lb-in (steel) |
| ASME B18.6.4 Type AB thread (in) | 3/8 | 12 TPI; basic .3750 | — | — | major .380 / .371; minor .309 / .299 | — | 3/4 (90° heads); 29/32 (csk heads) | 590 lb-in (steel) |
Mating features
Drawn at the exact size. Open press, slide, run and socket features by your process's clearance (tolerances by process); leave designed gaps and clamp fits as drawn.
| feature | exact | mates with | fit | files |
|---|---|---|---|---|
| Type AB thread | #8: 18 TPI, major .166 / .159 in, minor .122 / .116 in; #10: 16 TPI, major .189 / .182 in, minor .141 / .135 in (ASME B18.6.4) | pilot hole in sheet metal from sheet-metal-screw-pilot-holes (AFT: #8 drill 29, .1360 in; #10 drill 21, .1590 in) | designed | all |
Where the files are
Other publishers' files are linked, not hosted. "verify" = check the license at the link before commercial use.
| fasteners.eu | ISO 7049 pan head tapping screws with cross recess H and Z, form C and F: P, a, dk, k, r, rf, recess, ST2.2 to ST6.3 and lengths | web | Reference page; numbers only |
| HB Bolt | Type AB tapping screw thread (ASME B18.6.4-1998): basic diameter, threads per inch, major and minor diameter max / min, #2 to 3/8 | web | Maker cut sheet; numbers only. Headers jumbled in the text read |
| Cold-forged fastener maker sheet (hosted on a Shopify CDN, maker not named in the text read) | Threads for self-tapping screws, Type AB: same table with labelled columns including minimum practical screw length (90° and countersunk heads) and minimum torsional strength; cites ASME B18.6.3-2013 | web | Maker datasheet; numbers only |
Xem scan
File coming
No downloadable true-size file yet: the published figures do not fix the whole shape, and Xem never guesses a number. A measured scan is planned; request it and it moves up.
https://xemstudio.com/mcp to Claude, ChatGPT, Cursor or any MCP client (free, no account, one minute) and it can look up exact sizes, mating fits and free STEP/STL from every chat.Plain text: sheet.txt · JSON: /api/geometry?object=self-tapping-screws-iso-7049-pan-head
Fits with
Questions
What is the head diameter of an ST4.2 pan head screw?
ISO 7049: dk 8.2 mm max and 7.84 mm min, head height k 3.05 mm max and 2.75 mm min, pitch 1.4 mm, cross recess No. 2 (fasteners.eu).
How many threads per inch is a #8 Type AB screw?
18 TPI, major diameter .166 / .159 in and minor .122 / .116 in (HB Bolt, ASME B18.6.4; the same on a second sheet).
What does ST mean on a screw?
ST is the ISO 1478 tapping-screw thread series, for example ST4.2 with pitch 1.4 mm in ISO 7049; its major and minor diameters were not in the sources read here.