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Socket set screws, inch (ASME B18.3), cup point: hex key size, cup and flat point diameter, shortest length #0 to 1

What hex key, point diameter and minimum length does a 1/4-20 or #10-32 cup point socket set screw have? · Standard part · basis: ASME B18.3 hex socket set screw values as printed by AFT Fasteners, a maker sheet, fasten.it Table 5A and Torqbolt (the four agree); Travers Tool's sheet carries different point diameters and is shown as a second source; numbers only

Also called: cup point set screw dimensions, 1/4-20 set screw hex key size, 10-32 set screw allen key, 8-32 set screw hex key size, set screw cup point diameter, 3/8-16 set screw hex wrench, set screw minimum length, inch set screw hex key size chart, 5/16-18 set screw allen wrench, asme b18.3 set screw, 1/4-20 set screw cup point diameter, set screw shortest length

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
18 in table

Notes

  • Inch dimensions: hex key (socket) size J nominal, cup and flat point diameter C (max / min), and the shortest nominal screw length for cup and flat points, for cone and oval points, and for half dog points. AFT's, the maker sheet's, fasten.it's and Torqbolt's tables print the same numbers except that AFT's second table prints a 0.028 in hex key for #1 where the maker sheet, Torqbolt and fasten.it print 0.035 in (0.035 is shown); each has misaligned column headers (AFT's point diameters read min / max against Torqbolt's max / min, and fasten.it labels none of them), so the column assignment here was settled by order and cross-reading, and the C max / min pair is the one Torqbolt labels 'Cup and Flat Point Diameters, max, min'. Check the standard before you use C as a design value.
  • Disagreement shown, not resolved: Travers Tool's technical sheet prints a point diameter C of 0.125 / 0.114 in for 1/4, 0.156 / 0.144 for 5/16, 0.187 / 0.174 for 3/8 and 0.250 / 0.235 for 1/2 (and #4 0.056 / 0.051), smaller than the ASME B18.3 tables above (1/4: 0.132 / 0.118; 1/2: 0.291 / 0.270), and key engagement depths that also differ; it does not say which standard or revision it follows, so it is cited only as a second source here and its values are not on the table.
  • Key engagement (T) is not tabulated: the sources give it in several incompatible forms (one value per size in one sheet, short and long screw values in another). The standard also gives a cone-point angle of 90° (long screws) or 118° (short screws), +/- 2°, quoted by AFT.
  • Tightening torque and the shortest-length columns come from AFT's and the maker's second table (they agree); only the shortest lengths are shown. Metric set screws: set-screws-metric (M3 to M8, ISO 4026). Hex sockets, threads and cup profile: the cup is a point finish, not a published profile, so no model is drawn.
  • No file: the cup / flat point diameter C is the only published number of the point, the cup recess profile and the point chamfer are not published as numbers in any source read, so a drawing would be invented. McMaster-Carr sells socket set screws with per-part STEP; linked, not copied.

Socket set screws, inch (ASME B18.3), cup point: hex key size, cup… size chart

sizeTPI UNC / UNFhex key size J (nominal)cup / flat point dia C max / min (in)C max / min (mm, computed)shortest length: cup and flat (in)shortest length: cone and oval (in)shortest length: half dog (in)
#0— / 80.028 in0.033 / 0.0270.84 / 0.690.130.130.13
#164 / 72.035 in0.040 / 0.0331.02 / 0.840.130.190.13
#256 / 64.035 in0.047 / 0.0391.19 / 0.990.130.190.19
#348 / 56.050 in0.054 / 0.0451.37 / 1.140.190.190.19
#440 / 48.050 in0.061 / 0.0511.55 / 1.300.190.190.19
#540 / 441/16 in0.067 / 0.0571.70 / 1.450.190.190.19
#632 / 401/16 in0.074 / 0.0641.88 / 1.630.190.250.19
#832 / 365/64 in0.087 / 0.0762.21 / 1.930.190.250.25
#1024 / 323/32 in0.102 / 0.0882.59 / 2.240.190.250.25
1/420 / 281/8 in0.132 / 0.1183.35 / 3.000.250.310.31
5/1618 / 245/32 in0.172 / 0.1564.37 / 3.960.310.440.38
3/816 / 243/16 in0.212 / 0.1945.38 / 4.930.380.440.44
7/1614 / 207/32 in0.252 / 0.2326.40 / 5.890.440.630.50
1/213 / 201/4 in0.291 / 0.2707.39 / 6.860.500.630.63
5/811 / 185/16 in0.371 / 0.3479.42 / 8.810.630.880.88
3/410 / 163/8 in0.450 / 0.42511.43 / 10.790.751.001.00
7/89 / 141/2 in0.530 / 0.50213.46 / 12.750.881.001.00
18 / 129/16 in0.609 / 0.57915.47 / 14.711.001.251.25

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.

featureexactmates withfitfiles
hex socketnominal hex key size: #10 3/32, 1/4 1/8, 5/16 5/32, 3/8 3/16, 1/2 1/4 inhex key of the same sizeslideall
thread (major diameter)per size: #10 Ø4.826, 1/4 Ø6.350, 3/8 Ø9.525 mmtapped hole at the tap drill, see thread-reference-tap-drills-clearancedesignedall

Where the files are

Other publishers' files are linked, not hosted. "verify" = check the license at the link before commercial use.

AFT FastenersSocket set screws dimensions and mechanical properties (ASME B18.3-2003): hex key size S, shortest length, cup / flat point diameterwebPublisher's page; dimensions are facts
Fastener maker sheet (hosted on a Shopify CDN, ASME B18.3-2003 alloy steel)Socket set screws: shortest nominal length (cup / flat, cone / oval, half dog), hex key size and torque; dimension table (column headers shifted)webPublisher's page; dimensions are facts
fasten.itASME B18.3 Table 5A hex socket set screws, inch series (same values; headers garbled on the page)webPublisher's page; dimensions are facts
TorqboltASME B18.3 hexagon and spline socket set screws: J, C (cup / flat point diameter max), P (min) and the other columns, #0 to 2webPublisher's page; dimensions are facts
Travers ToolSocket set screw technical sheet: hex socket J, shortest length B, point diameter C, key engagement T (different values from the ASME B18.3 tables for the point and the key engagement)webPublisher's page; dimensions are facts
McMaster-CarrSocket head screws (cap, flat, set) (free STEP/IGES per part, for your own design use; no redistribution)STEP, IGES, PDFMcMaster-Carr site terms: personal design use, no redistribution verify

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Plain text: sheet.txt · JSON: /api/geometry?object=socket-set-screws-inch-asme-b18-3

Schematic, not to scale.

Fits with

Set screws (grub screws), M3–M8 (ISO 4026), isometric render of a generated part
Set screws (grub screws), M3–M8 (ISO 4026)5 sizes★ 27 files
Socket head cap screws, inch #0 to 1-1/2 (ASME B18.3): head, hex socket, key engagement — full size table + models #0 to 1, isometric render of a generated part
Socket head cap screws, inch #0 to 1-1/2 (ASME B18.3): head, hex socket, key engagement — full size table + models #0 to 150.8×38.1×76.2 mm★ 18 files
Flat head socket cap screws, inch (ASME B18.3, 82° countersunk) #0 to 1-1/2: head, hex socket, key engagement + models #0 to 1, isometric render of a generated part
Flat head socket cap screws, inch (ASME B18.3, 82° countersunk) #0 to 1-1/2: head, hex socket, key engagement + models #0 to 150.8×49.2×50.8 mm★ 18 files
Thread size reference: UNC / UNF and ISO metric coarse / fine — major, minor and pitch diameter, tap drill, clearance hole (close, normal, loose)201 sizes★ sheet
Flexible shaft couplers, 5–10 mm bores, isometric render of a generated part
Flexible shaft couplers, 5–10 mm bores6 sizes★ 6 files
Imperial machine screws: #4-40, #6-32, #8-32, 1/4-20, isometric render of a generated part
Imperial machine screws: #4-40, #6-32, #8-32, 1/4-204 sizes★ 18 files

Questions

What size allen key for a 1/4-20 set screw?

1/8 in hex key (ASME B18.3 nominal socket size).

What allen key for a #10-32 set screw?

3/32 in; cup point diameter 0.102 in max / 0.088 in min; shortest cup-point length 0.19 in.

What hex key for a 3/8-16 set screw?

3/16 in; cup and flat point diameter 0.212 / 0.194 in; shortest cup-point length 0.38 in.