{
 "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": "hex-bit-shank-iso-1173-1-4-in",
 "name": "Hex bit shank 1/4 in (ISO 1173 C 6.3 and E 6.3): across flats 6.35 mm, across corners 7.18 mm, form C and E dimensions, 4–12.5 mm sizes + hex pocket gauge",
 "kind": "standard",
 "category": "Hardware",
 "group": "Hand tool interfaces",
 "year": null,
 "question": "What are the dimensions of a 1/4 inch hex bit shank (C 6.3 / E 6.3), and what size hex pocket does a bit holder need?",
 "tags": [
  "hex bit",
  "screwdriver bit",
  "1/4 hex",
  "bit holder",
  "iso 1173",
  "c6.3",
  "e6.3",
  "quick change shank"
 ],
 "aliases": [
  "1/4 hex bit dimensions",
  "c6.3 bit dimensions",
  "e6.3 shank dimensions",
  "iso 1173",
  "hex bit shank size",
  "1/4 inch hex shank across flats",
  "bit holder hex pocket size",
  "6.35 mm hex",
  "screwdriver bit stl",
  "hex bit holder cad",
  "7/16 hex shank",
  "5/16 hex bit"
 ],
 "overall_mm": {
  "length": 86.6,
  "width": 28.7,
  "height": 12
 },
 "official_cad": false,
 "xem_status": "free-files",
 "les": false,
 "free_files": 1,
 "url": "https://xemstudio.com/objects/hex-bit-shank-iso-1173-1-4-in/",
 "sheet_txt": "https://xemstudio.com/objects/hex-bit-shank-iso-1173-1-4-in/sheet.txt",
 "sheet": {
  "basis": "ISO 1173 as transcribed from the 2001 edition (forms C and E), with the 1975 edition's s1 / e table as a cross-check; one Xem-drawn hex pocket gauge plate for holder design",
  "overall_mm": {
   "length": 86.6,
   "width": 28.7,
   "height": 12
  },
  "notes": [
   "The 1/4 in hex shank on screwdriver bits, nut drivers and quick-change chucks is ISO 1173 form C 6.3 (bit with a small ball groove, 25 mm bits) or form E 6.3 (power-tool shank with a deep groove, longer). Across flats s is 6.35 mm max and 6.29 mm min (h12) and across corners e is 7.18 mm max, 7.11 mm min. The same s / e numbers appear in the 1975 edition (6.350 / 6.292, 7.18 / 7.11), so they are stable across editions. The 1975 sample also gives 5/32 in (3.962 / 3.914), 5/16 in (7.930 / 7.872), 7/16 in (11.112 / 11.042), 5/8 in and 3/4 in (the 5/8 and 3/4 in sizes are ASME B107.4 sizes that ISO 1173:2001 does not carry).",
   "Letters D, A, B, C and R are as lettered in the transcribed 2001 table. The standard's figure was not available here, so what each measures (groove diameter, full-hex length, groove position, edge radius) is not stated and these columns are listed for lookup only, not drawn. One row of the transcription is flagged: the form E D value 4.7 for the 6.3 size reads smaller than the form C D 6.7, as printed. Hoffmann's data sheet for a C 6.3 bit adds only the overall length (25 mm).",
   "Holder design: the pocket across flats must be at least s max = 6.35 mm plus your process allowance; the pocket corners must clear e max 7.18 mm (a true hexagon of 6.35 mm has 7.33 mm across corners, which clears it). The gauge file is a plate with five through hexagon holes at the s max values for the C / E sizes, drawn at true size; it is an Xem example, not a published part.",
   "Not here: the ISO 1173 female hexagon forms (B, D, F, which is the holder's socket), Torx / Phillips / Pozidriv tip profiles, tolerances beyond s and e, magnetic holder geometry, and insert-bit lengths other than 25 mm."
  ],
  "table": {
   "columns": [
    "shank form",
    "nominal (mm)",
    "s max (mm)",
    "s min (mm)",
    "e max (mm)",
    "e min (mm)",
    "A (min)",
    "B",
    "D",
    "C",
    "R"
   ],
   "rows": [
    [
     "C (ball-groove, 25 mm bits)",
     "4",
     "3.96",
     "3.91",
     "4.48",
     "4.42",
     "9",
     "4",
     "—",
     "—",
     "—"
    ],
    [
     "C (ball-groove, 25 mm bits)",
     "6.3",
     "6.35",
     "6.29",
     "7.18",
     "7.11",
     "11",
     "8.2",
     "6.7",
     "—",
     "0.3"
    ],
    [
     "C (ball-groove, 25 mm bits)",
     "8",
     "7.93",
     "7.87",
     "8.96",
     "8.90",
     "13.5",
     "10.2",
     "8.2",
     "—",
     "—"
    ],
    [
     "C (ball-groove, 25 mm bits)",
     "12.5",
     "12.70",
     "12.63",
     "14.35",
     "14.27",
     "15.9",
     "12.7",
     "13.5",
     "—",
     "—"
    ],
    [
     "E (deep groove, power-tool shanks)",
     "6.3",
     "6.35",
     "6.29",
     "7.18",
     "7.11",
     "25",
     "~9.5",
     "4.7",
     "1 (C min)",
     "2.4"
    ],
    [
     "E (deep groove, power-tool shanks)",
     "8",
     "7.93",
     "7.87",
     "8.96",
     "8.90",
     "27",
     "~5.4",
     "6.3",
     "1.2 (C min)",
     "2.4"
    ],
    [
     "E (deep groove, power-tool shanks)",
     "11.2",
     "11.11",
     "11.04",
     "12.56",
     "12.48",
     "31.5",
     "~6.7",
     "8.7",
     "1.2 (C min)",
     "2.8"
    ],
    [
     "1975 edition: 5/32 in",
     "≈4",
     "3.962",
     "3.914",
     "4.48",
     "4.42",
     "—",
     "—",
     "—",
     "—",
     "—"
    ],
    [
     "1975 edition: 1/4 in",
     "≈6.3",
     "6.350",
     "6.292",
     "7.18",
     "7.11",
     "—",
     "—",
     "—",
     "—",
     "—"
    ],
    [
     "1975 edition: 5/16 in",
     "≈8",
     "7.930",
     "7.872",
     "8.96",
     "8.90",
     "—",
     "—",
     "—",
     "—",
     "—"
    ],
    [
     "1975 edition: 7/16 in",
     "—",
     "11.112",
     "11.042",
     "12.56",
     "12.48",
     "—",
     "—",
     "—",
     "—",
     "—"
    ],
    [
     "1975 edition: 5/8 in",
     "—",
     "15.875",
     "15.805",
     "17.94",
     "17.86",
     "—",
     "—",
     "—",
     "—",
     "—"
    ],
    [
     "1975 edition: 3/4 in",
     "—",
     "19.050",
     "18.966",
     "21.53",
     "21.43",
     "—",
     "—",
     "—",
     "—",
     "—"
    ]
   ]
  }
 },
 "sheet_text": "Hex bit shank 1/4 in (ISO 1173 C 6.3 and E 6.3): across flats 6.35 mm, across corners 7.18 mm, form C and E dimensions, 4–12.5 mm sizes + hex pocket gauge — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/hex-bit-shank-iso-1173-1-4-in/  (sheet CC BY 4.0)\nBasis: ISO 1173 as transcribed from the 2001 edition (forms C and E), with the 1975 edition's s1 / e table as a cross-check; one Xem-drawn hex pocket gauge plate for holder design\nCatalog version: 2026-10-20\n\nOverall (mm): length 86.6, width 28.7, height 12.0\n- The 1/4 in hex shank on screwdriver bits, nut drivers and quick-change chucks is ISO 1173 form C 6.3 (bit with a small ball groove, 25 mm bits) or form E 6.3 (power-tool shank with a deep groove, longer). Across flats s is 6.35 mm max and 6.29 mm min (h12) and across corners e is 7.18 mm max, 7.11 mm min. The same s / e numbers appear in the 1975 edition (6.350 / 6.292, 7.18 / 7.11), so they are stable across editions. The 1975 sample also gives 5/32 in (3.962 / 3.914), 5/16 in (7.930 / 7.872), 7/16 in (11.112 / 11.042), 5/8 in and 3/4 in (the 5/8 and 3/4 in sizes are ASME B107.4 sizes that ISO 1173:2001 does not carry).\n- Letters D, A, B, C and R are as lettered in the transcribed 2001 table. The standard's figure was not available here, so what each measures (groove diameter, full-hex length, groove position, edge radius) is not stated and these columns are listed for lookup only, not drawn. One row of the transcription is flagged: the form E D value 4.7 for the 6.3 size reads smaller than the form C D 6.7, as printed. Hoffmann's data sheet for a C 6.3 bit adds only the overall length (25 mm).\n- Holder design: the pocket across flats must be at least s max = 6.35 mm plus your process allowance; the pocket corners must clear e max 7.18 mm (a true hexagon of 6.35 mm has 7.33 mm across corners, which clears it). The gauge file is a plate with five through hexagon holes at the s max values for the C / E sizes, drawn at true size; it is an Xem example, not a published part.\n- Not here: the ISO 1173 female hexagon forms (B, D, F, which is the holder's socket), Torx / Phillips / Pozidriv tip profiles, tolerances beyond s and e, magnetic holder geometry, and insert-bit lengths other than 25 mm.\n\nshank form  nominal (mm)  s max (mm)  s min (mm)  e max (mm)  e min (mm)  A (min)  B  D  C  R\nC (ball-groove, 25 mm bits)  4  3.96  3.91  4.48  4.42  9  4  —  —  —\nC (ball-groove, 25 mm bits)  6.3  6.35  6.29  7.18  7.11  11  8.2  6.7  —  0.3\nC (ball-groove, 25 mm bits)  8  7.93  7.87  8.96  8.90  13.5  10.2  8.2  —  —\nC (ball-groove, 25 mm bits)  12.5  12.70  12.63  14.35  14.27  15.9  12.7  13.5  —  —\nE (deep groove, power-tool shanks)  6.3  6.35  6.29  7.18  7.11  25  ~9.5  4.7  1 (C min)  2.4\nE (deep groove, power-tool shanks)  8  7.93  7.87  8.96  8.90  27  ~5.4  6.3  1.2 (C min)  2.4\nE (deep groove, power-tool shanks)  11.2  11.11  11.04  12.56  12.48  31.5  ~6.7  8.7  1.2 (C min)  2.8\n1975 edition: 5/32 in  ≈4  3.962  3.914  4.48  4.42  —  —  —  —  —\n1975 edition: 1/4 in  ≈6.3  6.350  6.292  7.18  7.11  —  —  —  —  —\n1975 edition: 5/16 in  ≈8  7.930  7.872  8.96  8.90  —  —  —  —  —\n1975 edition: 7/16 in  —  11.112  11.042  12.56  12.48  —  —  —  —  —\n1975 edition: 5/8 in  —  15.875  15.805  17.94  17.86  —  —  —  —  —\n1975 edition: 3/4 in  —  19.050  18.966  21.53  21.43  —  —  —  —  —\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- ISO (iTeh Standards free sample): ISO 1173:1975 screwdriver bits / hexagon drives: male hexagon s1, e for 5/32, 1/4, 5/16, 7/16, 5/8, 3/4 in — web — Standards body sample pages; dimensions are facts — https://cdn.standards.iteh.ai/samples/5753/e09ec66c04eb4e148c53c7b553bb83f3/ISO-1173-1975.pdf\n- Wikipedia (screwdriver bit): ISO 1173:2001 shank form C and form E tables: S, D, E, A, B, C, R (transcribed) — web — CC BY-SA 4.0 (text, mirror of Wikipedia) — https://wiki.krisyotam.com/content/wikipedia_en_all_nopic_2026-03/Screwdriver_bit\n- Hoffmann Group: Bit, standard, 25 mm, hexagon 1/4 in C 6.3 (maker product page and data sheet) — web — Maker product page — https://hoffmann-group.com/GB/en/houk/p/01707-\n\nFree files (CC BY 4.0, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/hex-bit-shank-iso-1173-1-4-in/index.json\nAPI: https://xemstudio.com/api/geometry?object=hex-bit-shank-iso-1173-1-4-in\n",
 "sources": [
  {
   "publisher": "ISO (iTeh Standards free sample)",
   "title": "ISO 1173:1975 screwdriver bits / hexagon drives: male hexagon s1, e for 5/32, 1/4, 5/16, 7/16, 5/8, 3/4 in",
   "url": "https://cdn.standards.iteh.ai/samples/5753/e09ec66c04eb4e148c53c7b553bb83f3/ISO-1173-1975.pdf",
   "formats": [
    "web"
   ],
   "license": "Standards body sample pages; dimensions are facts",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Wikipedia (screwdriver bit)",
   "title": "ISO 1173:2001 shank form C and form E tables: S, D, E, A, B, C, R (transcribed)",
   "url": "https://wiki.krisyotam.com/content/wikipedia_en_all_nopic_2026-03/Screwdriver_bit",
   "formats": [
    "web"
   ],
   "license": "CC BY-SA 4.0 (text, mirror of Wikipedia)",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Hoffmann Group",
   "title": "Bit, standard, 25 mm, hexagon 1/4 in C 6.3 (maker product page and data sheet)",
   "url": "https://hoffmann-group.com/GB/en/houk/p/01707-",
   "formats": [
    "web"
   ],
   "license": "Maker product page",
   "license_verified": true,
   "hosted": false
  }
 ],
 "xem": {
  "status": "free-files",
  "sheet_free": true,
  "mesh_price_usd": null,
  "step_price_usd": null,
  "tolerance_mm": null
 },
 "related": [
  "hex-keys-iso-2936-asme-b18-3",
  "square-drive-iso-1174-1-4-to-1-in",
  "socket-head-cap-screws-metric",
  "rc-wheel-hex-7mm"
 ],
 "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": "shank across flats s",
   "exact": "6.35 mm max / 6.29 mm min (1/4 in, C 6.3 and E 6.3); also 3.96, 7.93, 11.11, 12.70 mm",
   "mates": "hex pocket in a bit holder, chuck or driver handle: at least s max plus your process allowance",
   "fit": "slide",
   "files": "hex-bit-holder"
  },
  {
   "feature": "across corners e",
   "exact": "7.18 mm max / 7.11 mm min for 6.3",
   "mates": "pocket corners must clear e max (a true hexagon of 6.35 mm across flats has 7.33 mm across corners)",
   "fit": "slide",
   "files": "hex-bit-holder"
  }
 ],
 "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 is the across-flats size of a 1/4 inch hex bit?",
   "a": "6.35 mm maximum and 6.29 mm minimum (ISO 1173 C 6.3 and E 6.3), 7.18 mm maximum across corners."
  },
  {
   "q": "What is the difference between C 6.3 and E 6.3?",
   "a": "Both are 6.3 mm hexagons. C 6.3 is the bit shank with a small groove (25 mm bits), E 6.3 is the power-tool shank with a deep groove and a longer minimum length (25 against 11 mm in the A column)."
  },
  {
   "q": "What size hex pocket should a bit holder have?",
   "a": "At least 6.35 mm across flats (the shank's maximum) plus your process allowance for a slide fit; the gauge plate shows the true 6.35 mm size."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "file": "hex-bit-holder-gauge-4-6-3-8-11-2-12-5",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/hex-bit-shank-iso-1173-1-4-in/hex-bit-holder-gauge-4-6-3-8-11-2-12-5.step",
   "stl": "https://xemstudio.com/files/hardware/hex-bit-shank-iso-1173-1-4-in/hex-bit-holder-gauge-4-6-3-8-11-2-12-5.stl",
   "note": "hex pocket gauge plate, 86.6 × 28.7 × 12 mm: five through hexagon holes at the ISO 1173 s max across flats 3.96, 6.35 (1/4 in), 7.93, 11.11 and 12.70 mm, smallest first, 6 mm between the holes' across-corners extents; plate size, thickness and corner radius are Xem choices; hole sizes are the shank's own maximum, so add your process allowance to them"
  }
 ],
 "markdown": "https://xemstudio.com/objects/hex-bit-shank-iso-1173-1-4-in/index.md"
}