{
 "version": "2026-10-20",
 "license": "Dimension sheets: CC BY 4.0. Standard and published-size files: CC BY 4.0. Xem Studio's own designs (files_license = Xem Studio Design License): free to use and sell things from, not to redistribute as files — https://xemstudio.com/license/. Other publishers' files: their own license, linked beside them.",
 "slug": "socket-set-screws-inch-asme-b18-3",
 "name": "Socket set screws, inch (ASME B18.3), cup point: hex key size, cup and flat point diameter, shortest length #0 to 1",
 "kind": "standard",
 "category": "Hardware",
 "group": "Fasteners",
 "year": null,
 "question": "What hex key, point diameter and minimum length does a 1/4-20 or #10-32 cup point socket set screw have?",
 "tags": [
  "set screw",
  "grub screw",
  "cup point",
  "hex socket set screw",
  "allen set screw",
  "asme b18.3",
  "inch",
  "fastener",
  "headless",
  "container"
 ],
 "aliases": [
  "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"
 ],
 "overall_mm": {
  "length": null,
  "width": null,
  "height": null
 },
 "official_cad": false,
 "xem_status": "not-scanned",
 "les": false,
 "free_files": 0,
 "url": "https://xemstudio.com/objects/socket-set-screws-inch-asme-b18-3/",
 "sheet_txt": "https://xemstudio.com/objects/socket-set-screws-inch-asme-b18-3/sheet.txt",
 "sheet": {
  "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",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "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."
  ],
  "table": {
   "columns": [
    "size",
    "TPI UNC / UNF",
    "hex 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)"
   ],
   "rows": [
    [
     "#0",
     "— / 80",
     ".028 in",
     "0.033 / 0.027",
     "0.84 / 0.69",
     "0.13",
     "0.13",
     "0.13"
    ],
    [
     "#1",
     "64 / 72",
     ".035 in",
     "0.040 / 0.033",
     "1.02 / 0.84",
     "0.13",
     "0.19",
     "0.13"
    ],
    [
     "#2",
     "56 / 64",
     ".035 in",
     "0.047 / 0.039",
     "1.19 / 0.99",
     "0.13",
     "0.19",
     "0.19"
    ],
    [
     "#3",
     "48 / 56",
     ".050 in",
     "0.054 / 0.045",
     "1.37 / 1.14",
     "0.19",
     "0.19",
     "0.19"
    ],
    [
     "#4",
     "40 / 48",
     ".050 in",
     "0.061 / 0.051",
     "1.55 / 1.30",
     "0.19",
     "0.19",
     "0.19"
    ],
    [
     "#5",
     "40 / 44",
     "1/16 in",
     "0.067 / 0.057",
     "1.70 / 1.45",
     "0.19",
     "0.19",
     "0.19"
    ],
    [
     "#6",
     "32 / 40",
     "1/16 in",
     "0.074 / 0.064",
     "1.88 / 1.63",
     "0.19",
     "0.25",
     "0.19"
    ],
    [
     "#8",
     "32 / 36",
     "5/64 in",
     "0.087 / 0.076",
     "2.21 / 1.93",
     "0.19",
     "0.25",
     "0.25"
    ],
    [
     "#10",
     "24 / 32",
     "3/32 in",
     "0.102 / 0.088",
     "2.59 / 2.24",
     "0.19",
     "0.25",
     "0.25"
    ],
    [
     "1/4",
     "20 / 28",
     "1/8 in",
     "0.132 / 0.118",
     "3.35 / 3.00",
     "0.25",
     "0.31",
     "0.31"
    ],
    [
     "5/16",
     "18 / 24",
     "5/32 in",
     "0.172 / 0.156",
     "4.37 / 3.96",
     "0.31",
     "0.44",
     "0.38"
    ],
    [
     "3/8",
     "16 / 24",
     "3/16 in",
     "0.212 / 0.194",
     "5.38 / 4.93",
     "0.38",
     "0.44",
     "0.44"
    ],
    [
     "7/16",
     "14 / 20",
     "7/32 in",
     "0.252 / 0.232",
     "6.40 / 5.89",
     "0.44",
     "0.63",
     "0.50"
    ],
    [
     "1/2",
     "13 / 20",
     "1/4 in",
     "0.291 / 0.270",
     "7.39 / 6.86",
     "0.50",
     "0.63",
     "0.63"
    ],
    [
     "5/8",
     "11 / 18",
     "5/16 in",
     "0.371 / 0.347",
     "9.42 / 8.81",
     "0.63",
     "0.88",
     "0.88"
    ],
    [
     "3/4",
     "10 / 16",
     "3/8 in",
     "0.450 / 0.425",
     "11.43 / 10.79",
     "0.75",
     "1.00",
     "1.00"
    ],
    [
     "7/8",
     "9 / 14",
     "1/2 in",
     "0.530 / 0.502",
     "13.46 / 12.75",
     "0.88",
     "1.00",
     "1.00"
    ],
    [
     "1",
     "8 / 12",
     "9/16 in",
     "0.609 / 0.579",
     "15.47 / 14.71",
     "1.00",
     "1.25",
     "1.25"
    ]
   ]
  }
 },
 "sheet_text": "Socket set screws, inch (ASME B18.3), cup point: hex key size, cup and flat point diameter, shortest length #0 to 1 — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/socket-set-screws-inch-asme-b18-3/  (sheet CC BY 4.0)\nBasis: 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\nCatalog version: 2026-10-20\n\nSizes: see table below\n- 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.\n- 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.\n- 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.\n- 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.\n- 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.\n\nsize  TPI UNC / UNF  hex 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)\n#0  — / 80  .028 in  0.033 / 0.027  0.84 / 0.69  0.13  0.13  0.13\n#1  64 / 72  .035 in  0.040 / 0.033  1.02 / 0.84  0.13  0.19  0.13\n#2  56 / 64  .035 in  0.047 / 0.039  1.19 / 0.99  0.13  0.19  0.19\n#3  48 / 56  .050 in  0.054 / 0.045  1.37 / 1.14  0.19  0.19  0.19\n#4  40 / 48  .050 in  0.061 / 0.051  1.55 / 1.30  0.19  0.19  0.19\n#5  40 / 44  1/16 in  0.067 / 0.057  1.70 / 1.45  0.19  0.19  0.19\n#6  32 / 40  1/16 in  0.074 / 0.064  1.88 / 1.63  0.19  0.25  0.19\n#8  32 / 36  5/64 in  0.087 / 0.076  2.21 / 1.93  0.19  0.25  0.25\n#10  24 / 32  3/32 in  0.102 / 0.088  2.59 / 2.24  0.19  0.25  0.25\n1/4  20 / 28  1/8 in  0.132 / 0.118  3.35 / 3.00  0.25  0.31  0.31\n5/16  18 / 24  5/32 in  0.172 / 0.156  4.37 / 3.96  0.31  0.44  0.38\n3/8  16 / 24  3/16 in  0.212 / 0.194  5.38 / 4.93  0.38  0.44  0.44\n7/16  14 / 20  7/32 in  0.252 / 0.232  6.40 / 5.89  0.44  0.63  0.50\n1/2  13 / 20  1/4 in  0.291 / 0.270  7.39 / 6.86  0.50  0.63  0.63\n5/8  11 / 18  5/16 in  0.371 / 0.347  9.42 / 8.81  0.63  0.88  0.88\n3/4  10 / 16  3/8 in  0.450 / 0.425  11.43 / 10.79  0.75  1.00  1.00\n7/8  9 / 14  1/2 in  0.530 / 0.502  13.46 / 12.75  0.88  1.00  1.00\n1  8 / 12  9/16 in  0.609 / 0.579  15.47 / 14.71  1.00  1.25  1.25\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- AFT Fasteners: Socket set screws dimensions and mechanical properties (ASME B18.3-2003): hex key size S, shortest length, cup / flat point diameter — web — Publisher's page; dimensions are facts — https://www.aftfasteners.com/socket-set-screws-dimensions-mechanical-properties/\n- 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) — web — Publisher's page; dimensions are facts — https://cdn2.shopify.com/s/files/1/0056/7856/3437/files/SocketsSetscr.pdf\n- fasten.it: ASME B18.3 Table 5A hex socket set screws, inch series (same values; headers garbled on the page) — web — Publisher's page; dimensions are facts — https://fasten.it/en/norms/norm/asme_b18.3_table_5a\n- Torqbolt: ASME B18.3 hexagon and spline socket set screws: J, C (cup / flat point diameter max), P (min) and the other columns, #0 to 2 — web — Publisher's page; dimensions are facts — https://torqbolt.com/asme-b18-3-hexagon-and-spline-socket-set-screws-dimensions-standards-specifications\n- Travers Tool: Socket 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) — web — Publisher's page; dimensions are facts — https://docs.travers.com/assets/pdf/597971_tech.pdf\n- McMaster-Carr: Socket head screws (cap, flat, set) (free STEP/IGES per part, for your own design use; no redistribution) — STEP, IGES, PDF — McMaster-Carr site terms: personal design use, no redistribution [verify license at link] — https://www.mcmaster.com/products/socket-head-screws/\n\nNo true-size file yet: the published figures do not fix the whole shape; a measured scan is planned.\nAPI: https://xemstudio.com/api/geometry?object=socket-set-screws-inch-asme-b18-3\n",
 "sources": [
  {
   "publisher": "AFT Fasteners",
   "title": "Socket set screws dimensions and mechanical properties (ASME B18.3-2003): hex key size S, shortest length, cup / flat point diameter",
   "url": "https://www.aftfasteners.com/socket-set-screws-dimensions-mechanical-properties/",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Fastener maker sheet (hosted on a Shopify CDN, ASME B18.3-2003 alloy steel)",
   "title": "Socket set screws: shortest nominal length (cup / flat, cone / oval, half dog), hex key size and torque; dimension table (column headers shifted)",
   "url": "https://cdn2.shopify.com/s/files/1/0056/7856/3437/files/SocketsSetscr.pdf",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "fasten.it",
   "title": "ASME B18.3 Table 5A hex socket set screws, inch series (same values; headers garbled on the page)",
   "url": "https://fasten.it/en/norms/norm/asme_b18.3_table_5a",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Torqbolt",
   "title": "ASME B18.3 hexagon and spline socket set screws: J, C (cup / flat point diameter max), P (min) and the other columns, #0 to 2",
   "url": "https://torqbolt.com/asme-b18-3-hexagon-and-spline-socket-set-screws-dimensions-standards-specifications",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Travers Tool",
   "title": "Socket 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)",
   "url": "https://docs.travers.com/assets/pdf/597971_tech.pdf",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "McMaster-Carr",
   "title": "Socket head screws (cap, flat, set) (free STEP/IGES per part, for your own design use; no redistribution)",
   "url": "https://www.mcmaster.com/products/socket-head-screws/",
   "formats": [
    "STEP",
    "IGES",
    "PDF"
   ],
   "license": "McMaster-Carr site terms: personal design use, no redistribution",
   "license_verified": false,
   "hosted": false
  }
 ],
 "xem": {
  "status": "not-scanned",
  "sheet_free": true,
  "mesh_price_usd": null,
  "step_price_usd": null,
  "tolerance_mm": null
 },
 "related": [
  "set-screws-metric",
  "socket-head-cap-screws-inch-full",
  "flat-head-socket-cap-screws-inch",
  "thread-reference-tap-drills-clearance",
  "shaft-couplers",
  "imperial-machine-screws",
  "set-screws-metric-m10-m12-and-point-types",
  "hex-keys-iso-2936-asme-b18-3"
 ],
 "fits": [],
 "dimensions": "exact (nominal, no tolerance added)",
 "dimension_rule": "All geometry on Xem Studio is exact (nominal, true size) with no tolerance added. Where a part meets another part, the object lists its mating features (feature, exact size, what it mates with, fit class: press, slide, run, socket, clamp or designed). Apply your process's allowance to those features only; 'designed' gaps are part of the design and stay as drawn. Typical accuracy by process and ISO 286 fits: https://xemstudio.com/tolerances/",
 "mating": [
  {
   "feature": "hex socket",
   "exact": "nominal hex key size: #10 3/32, 1/4 1/8, 5/16 5/32, 3/8 3/16, 1/2 1/4 in",
   "mates": "hex key of the same size",
   "fit": "slide",
   "files": "all"
  },
  {
   "feature": "thread (major diameter)",
   "exact": "per size: #10 Ø4.826, 1/4 Ø6.350, 3/8 Ø9.525 mm",
   "mates": "tapped hole at the tap drill, see thread-reference-tap-drills-clearance",
   "fit": "designed",
   "files": "all"
  }
 ],
 "fit_classes": {
  "press": "stays put: pin, tube, bearing or magnet held by interference. ISO 286 equivalent: H7/p6 (locational interference) or tighter.",
  "slide": "assembles by hand and is held by a grub, pinch or clamp: shaft in a hub, rod in a socket, spigot in a bore. ISO 286 equivalent: H7/g6 or H7/h6.",
  "run": "turns or slides in use: pin in a link, rod through a guide. ISO 286 equivalent: H8/f7 (close running).",
  "socket": "large sliding fit: syringe barrel, sleeve, bobbin in a bore. ISO 286 equivalent: H9/d9 (free running) or looser.",
  "clamp": "split part that closes on the mating part with screws: make it at size.",
  "designed": "a gap that is part of the design (piston fit option, displacer gap, air gap): do not change."
 },
 "faq": [
  {
   "q": "What size allen key for a 1/4-20 set screw?",
   "a": "1/8 in hex key (ASME B18.3 nominal socket size)."
  },
  {
   "q": "What allen key for a #10-32 set screw?",
   "a": "3/32 in; cup point diameter 0.102 in max / 0.088 in min; shortest cup-point length 0.19 in."
  },
  {
   "q": "What hex key for a 3/8-16 set screw?",
   "a": "3/16 in; cup and flat point diameter 0.212 / 0.194 in; shortest cup-point length 0.38 in."
  }
 ],
 "files_license": null,
 "offers": [],
 "markdown": "https://xemstudio.com/objects/socket-set-screws-inch-asme-b18-3/index.md"
}