# 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?

- Category: Hardware › Fasteners
- Kind: 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
- Page: https://xemstudio.com/objects/self-tapping-screws-iso-7049-pan-head/ · JSON: https://xemstudio.com/api/geometry?object=self-tapping-screws-iso-7049-pan-head · Plain text: https://xemstudio.com/objects/self-tapping-screws-iso-7049-pan-head/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); files CC BY 4.0 or their publisher's license
- Use in every chat: add https://xemstudio.com/mcp as a connector (https://xemstudio.com/use-with-ai/)

**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

- 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.

## 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 |
|---|---|---|---|---|
| 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 |

## Sizes

| 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) |

## Where the files are

- 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](https://www.fasteners.eu/standards/ISO/7049/) — 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](https://www.hbbolt.com/_Product_Cut_Sheets/TypeABPointInfo.pdf) — 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](https://cdn2.shopify.com/s/files/1/0056/7856/3437/files/SttypeAB.pdf) — web — Maker datasheet; numbers only

## 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.

## Fits with

- [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)](https://xemstudio.com/objects/sheet-metal-screw-pilot-holes/)
- [Thread-forming screws for plastic (EJOT PT type): screw hole diameter by plastic, M2.2–M4, boss hole rule, K sizes](https://xemstudio.com/objects/plastic-thread-forming-screw-holes/)
- [Imperial machine screws: #4-40, #6-32, #8-32, 1/4-20](https://xemstudio.com/objects/imperial-machine-screws/)
- [Flat-head wood screws, inch #4–#14 (ASME B18.6.1): body and head diameter, pilot and clearance holes from three sources + envelope models](https://xemstudio.com/objects/wood-screws-flat-head-inch/)
- [Rivet nuts (blind threaded inserts), flat head: hole size, grip range, body and flange dimensions, M3–M12 and #6-32 to 3/8-16](https://xemstudio.com/objects/rivet-nuts-flat-head/)
- [Blind (pop) rivets, dome head: 3.2, 4.0, 4.8 mm and 1/8, 5/32, 3/16 in: hole size, head diameter, grip range, length](https://xemstudio.com/objects/blind-pop-rivets-dome-head/)
- [Self-drilling screws DIN 7504: hexagon washer head (type K) and pan / countersunk heads (N, P), ST2.2–ST6.3: head diameter, height, drill-point diameter, drilling depth](https://xemstudio.com/objects/self-drilling-screws-din-7504-heads/)
- [Tek / self-drilling screw drill points #1 to #5: how thick a steel each point drills (four sources, shown side by side)](https://xemstudio.com/objects/tek-self-drilling-screw-drill-points/)