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
Source: Xem Studio, https://xemstudio.com/objects/steep-taper-7-24-cat-bt-nmtb-30-40-50/  (sheet CC BY 4.0)
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
Catalog version: 2026-10-20

Sizes: see table below
- 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.

family  size  gauge diameter D1 (mm)  flange diameter (mm)  length (mm)  flange thickness (mm)  draw bar thread
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)

Files elsewhere (not hosted by Xem Studio; license as stated by the publisher):
- 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
- 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
- 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
- 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

No true-size file yet: the published figures do not fix the whole shape; a measured scan is planned.
API: https://xemstudio.com/api/geometry?object=steep-taper-7-24-cat-bt-nmtb-30-40-50