{
 "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": "steep-taper-7-24-cat-bt-nmtb-30-40-50",
 "name": "7:24 tool-holder tapers 30, 40, 50: CAT, BT and NMTB gauge diameter, flange diameter, length and draw bar thread (CAT40, BT40, DIN 2080)",
 "kind": "standard",
 "category": "Hardware",
 "group": "Machine tool tapers & collets",
 "year": null,
 "question": "What are the dimensions of a CAT40 and BT40 tool holder taper (gauge diameter, flange, length, pull stud thread)?",
 "tags": [
  "cat40",
  "bt40",
  "bt30",
  "cat50",
  "7:24 taper",
  "tool holder",
  "nmtb",
  "iso 7388",
  "spindle taper",
  "pull stud",
  "container"
 ],
 "aliases": [
  "cat40 dimensions",
  "bt40 dimensions",
  "cat40 vs bt40",
  "7:24 taper dimensions",
  "cat40 taper gauge diameter",
  "bt30 dimensions",
  "cat50 flange diameter",
  "bt40 pull stud thread",
  "nmtb 40 taper",
  "cat40 flange thickness",
  "bt40 flange thickness",
  "iso 7388 7:24",
  "r8 collet dimensions"
 ],
 "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/steep-taper-7-24-cat-bt-nmtb-30-40-50/",
 "sheet_txt": "https://xemstudio.com/objects/steep-taper-7-24-cat-bt-nmtb-30-40-50/sheet.txt",
 "sheet": {
  "basis": "Tools-n-Gizmos' taper specification page (inch and metric tables) with CAT 40 / BT 40 values cross-checked against Industrial Monitor Direct; numbers only",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "Steep (7:24) tool-holder tapers taper 7 mm in diameter per 24 mm of length (about 16.6° included). Sizes 30, 40 and 50 share the gauge diameter 31.75, 44.45 and 69.85 mm (1.250, 1.750, 2.750 in) across the CAT (V-flange, ANSI B5.50), BT (Japanese JIS B6339) and NMTB (ANSI B5.18, DIN 2080) families; they differ in flange, length, flange thickness and the draw-bar (pull stud) thread, so CAT and BT holders are not interchangeable. Length columns are as printed (L for CAT and BT, L1 for NMTB).",
   "Cross-check: Industrial Monitor Direct gives CAT 40 flange thickness 19.1 mm (0.750 in = 19.05 mm here), BT 40 27.0 mm (1.063 in = 27.0 mm), pull stud thread M16 × 2 (and 5/8-11 for CAT), drive-key width 16.1 mm for both, and gauge line to pull stud face 68.4 mm for CAT 40 and 65.4 mm for BT 40 (68.25 mm in the table here: a 0.15 mm difference kept, not averaged). Drive-dog face to face 48.8 / 45.2 mm is from the same article.",
   "Disagreements inside the source page: the CAT 30 flange is 46.02 mm in the inch table and 50 mm in the metric table; NMTB 50 flange is 3.500 in = 88.9 mm in the inch table and 97.5 mm in the metric table; NMTB 30 / 40 lengths differ by 0.06 and 0.33 mm between the two tables; the CAT 30 draw-bar thread is 1/2-13 in one place and 1/2-16 in another. Both are shown. NMTB flange thickness is not clearly labelled in the source and is left blank. The ISO 7388-1 / ANSI / JIS numbers themselves were not read from the standards (paywalled), so check a gauge or the standard before cutting a spindle.",
   "No files: a holder taper is defined by a gauge diameter and 7:24 but the flange, keyway, retention-knob recess and pull-stud thread depth are not published as complete numbers in the sources read. R8 (Bridgeport) is not on this page: no dimension table was found, only forum posts and a hobby page with partial numbers (included angle 16° 51', drawbar thread 7/16-20), which are not enough to draw or tabulate."
  ],
  "table": {
   "columns": [
    "family",
    "size",
    "gauge diameter D1 (mm)",
    "flange diameter (mm)",
    "length (mm)",
    "flange thickness (mm)",
    "draw bar thread"
   ],
   "rows": [
    [
     "CAT (V-flange, ANSI B5.50 / ISO 7388-1)",
     "30",
     "31.75",
     "46.02 (metric table 50)",
     "47.63",
     "19.05",
     "1/2-13 (metric table M12)"
    ],
    [
     "CAT (V-flange, ANSI B5.50 / ISO 7388-1)",
     "40",
     "44.45",
     "63.05",
     "68.25",
     "19.05",
     "5/8-11 (metric table M16)"
    ],
    [
     "CAT (V-flange, ANSI B5.50 / ISO 7388-1)",
     "50",
     "69.85",
     "98.41",
     "101.60",
     "19.05",
     "1-8 (metric table M24)"
    ],
    [
     "BT (JIS B6339 / ISO 7388-1)",
     "30",
     "31.75",
     "46.00",
     "48.40",
     "22.00",
     "M12"
    ],
    [
     "BT (JIS B6339 / ISO 7388-1)",
     "40",
     "44.45",
     "63.00",
     "65.40",
     "27.00",
     "M16"
    ],
    [
     "BT (JIS B6339 / ISO 7388-1)",
     "50",
     "69.85",
     "100.00",
     "101.80",
     "38.00",
     "M24"
    ],
    [
     "NMTB (ANSI B5.18 / DIN 2080)",
     "30",
     "31.75",
     "46.02 (metric table 50)",
     "68.33 (metric table 68.39)",
     "—",
     "1/2-13 (metric table M12)"
    ],
    [
     "NMTB (ANSI B5.18 / DIN 2080)",
     "40",
     "44.45",
     "63.5 (metric table 63)",
     "93.73 (metric table 93.40)",
     "—",
     "5/8-11 (metric table M16)"
    ],
    [
     "NMTB (ANSI B5.18 / DIN 2080)",
     "50",
     "69.85",
     "88.9 (metric table 97.5)",
     "127.0",
     "—",
     "1-8 (metric table M24)"
    ]
   ]
  }
 },
 "sheet_text": "7:24 tool-holder tapers 30, 40, 50: CAT, BT and NMTB gauge diameter, flange diameter, length and draw bar thread (CAT40, BT40, DIN 2080) — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/steep-taper-7-24-cat-bt-nmtb-30-40-50/  (sheet CC BY 4.0)\nBasis: Tools-n-Gizmos' taper specification page (inch and metric tables) with CAT 40 / BT 40 values cross-checked against Industrial Monitor Direct; numbers only\nCatalog version: 2026-10-20\n\nSizes: see table below\n- Steep (7:24) tool-holder tapers taper 7 mm in diameter per 24 mm of length (about 16.6° included). Sizes 30, 40 and 50 share the gauge diameter 31.75, 44.45 and 69.85 mm (1.250, 1.750, 2.750 in) across the CAT (V-flange, ANSI B5.50), BT (Japanese JIS B6339) and NMTB (ANSI B5.18, DIN 2080) families; they differ in flange, length, flange thickness and the draw-bar (pull stud) thread, so CAT and BT holders are not interchangeable. Length columns are as printed (L for CAT and BT, L1 for NMTB).\n- Cross-check: Industrial Monitor Direct gives CAT 40 flange thickness 19.1 mm (0.750 in = 19.05 mm here), BT 40 27.0 mm (1.063 in = 27.0 mm), pull stud thread M16 × 2 (and 5/8-11 for CAT), drive-key width 16.1 mm for both, and gauge line to pull stud face 68.4 mm for CAT 40 and 65.4 mm for BT 40 (68.25 mm in the table here: a 0.15 mm difference kept, not averaged). Drive-dog face to face 48.8 / 45.2 mm is from the same article.\n- Disagreements inside the source page: the CAT 30 flange is 46.02 mm in the inch table and 50 mm in the metric table; NMTB 50 flange is 3.500 in = 88.9 mm in the inch table and 97.5 mm in the metric table; NMTB 30 / 40 lengths differ by 0.06 and 0.33 mm between the two tables; the CAT 30 draw-bar thread is 1/2-13 in one place and 1/2-16 in another. Both are shown. NMTB flange thickness is not clearly labelled in the source and is left blank. The ISO 7388-1 / ANSI / JIS numbers themselves were not read from the standards (paywalled), so check a gauge or the standard before cutting a spindle.\n- No files: a holder taper is defined by a gauge diameter and 7:24 but the flange, keyway, retention-knob recess and pull-stud thread depth are not published as complete numbers in the sources read. R8 (Bridgeport) is not on this page: no dimension table was found, only forum posts and a hobby page with partial numbers (included angle 16° 51', drawbar thread 7/16-20), which are not enough to draw or tabulate.\n\nfamily  size  gauge diameter D1 (mm)  flange diameter (mm)  length (mm)  flange thickness (mm)  draw bar thread\nCAT (V-flange, ANSI B5.50 / ISO 7388-1)  30  31.75  46.02 (metric table 50)  47.63  19.05  1/2-13 (metric table M12)\nCAT (V-flange, ANSI B5.50 / ISO 7388-1)  40  44.45  63.05  68.25  19.05  5/8-11 (metric table M16)\nCAT (V-flange, ANSI B5.50 / ISO 7388-1)  50  69.85  98.41  101.60  19.05  1-8 (metric table M24)\nBT (JIS B6339 / ISO 7388-1)  30  31.75  46.00  48.40  22.00  M12\nBT (JIS B6339 / ISO 7388-1)  40  44.45  63.00  65.40  27.00  M16\nBT (JIS B6339 / ISO 7388-1)  50  69.85  100.00  101.80  38.00  M24\nNMTB (ANSI B5.18 / DIN 2080)  30  31.75  46.02 (metric table 50)  68.33 (metric table 68.39)  —  1/2-13 (metric table M12)\nNMTB (ANSI B5.18 / DIN 2080)  40  44.45  63.5 (metric table 63)  93.73 (metric table 93.40)  —  5/8-11 (metric table M16)\nNMTB (ANSI B5.18 / DIN 2080)  50  69.85  88.9 (metric table 97.5)  127.0  —  1-8 (metric table M24)\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- Tools-n-Gizmos: Taper specifications: Morse overall length L1, socket depth L2, tang L3; CAT, BT and NMTB 7:24 gauge diameter, flange, length, draw bar thread — web — Publisher's page; dimensions are facts — https://tools-n-gizmos.com/specs/Tapers.html\n- Industrial Monitor Direct: CAT 40 vs BT 40: flange thickness, pull stud thread, drive key width, gauge line to pull stud face — web — Publisher's page; dimensions are facts — https://industrialmonitordirect.com/blogs/knowledgebase/cat-40-vs-bt-40-taper-key-differences-specifications\n- McMaster-Carr: CAT 40 taper end mill holders (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/cat-40\n- McMaster-Carr: Pull studs / retention knobs (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/pull-studs\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=steep-taper-7-24-cat-bt-nmtb-30-40-50\n",
 "sources": [
  {
   "publisher": "Tools-n-Gizmos",
   "title": "Taper specifications: Morse overall length L1, socket depth L2, tang L3; CAT, BT and NMTB 7:24 gauge diameter, flange, length, draw bar thread",
   "url": "https://tools-n-gizmos.com/specs/Tapers.html",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Industrial Monitor Direct",
   "title": "CAT 40 vs BT 40: flange thickness, pull stud thread, drive key width, gauge line to pull stud face",
   "url": "https://industrialmonitordirect.com/blogs/knowledgebase/cat-40-vs-bt-40-taper-key-differences-specifications",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "McMaster-Carr",
   "title": "CAT 40 taper end mill holders (free STEP/IGES per part, for your own design use; no redistribution)",
   "url": "https://www.mcmaster.com/products/cat-40",
   "formats": [
    "STEP",
    "IGES",
    "PDF"
   ],
   "license": "McMaster-Carr site terms: personal design use, no redistribution",
   "license_verified": false,
   "hosted": false
  },
  {
   "publisher": "McMaster-Carr",
   "title": "Pull studs / retention knobs (free STEP/IGES per part, for your own design use; no redistribution)",
   "url": "https://www.mcmaster.com/pull-studs",
   "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": [
  "morse-tapers-mt0-mt7",
  "er-collets-er8-er50"
 ],
 "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": [],
 "faq": [
  {
   "q": "What is the gauge diameter of a CAT40 taper?",
   "a": "44.45 mm (1.750 in), the same as BT40; the CAT flange is 63.05 mm, the BT flange 63.00 mm."
  },
  {
   "q": "What is the pull stud thread of a BT40 holder?",
   "a": "M16 (M16 × 2.0 in Industrial Monitor Direct); CAT 40 uses 5/8-11 in the inch table."
  },
  {
   "q": "Are CAT40 and BT40 interchangeable?",
   "a": "No: the taper is the same but the flange thickness (19.05 against 27.0 mm), drive-key location and pull stud differ."
  }
 ],
 "files_license": null,
 "offers": [],
 "markdown": "https://xemstudio.com/objects/steep-taper-7-24-cat-bt-nmtb-30-40-50/index.md"
}