Arbor & Taper Chart

Morse, Jacobs and B tapers, 7:24 steep tapers (DIN 2080, SK, BT, CAT), R8, shell mill and horizontal milling arbors, with line drawings.

Download PDF (4 pages, A4)Shop arbors and chucks

Nominal dimensions for identifying tapers and arbors - not gauging figures. Drawings not to scale; tapers exaggerated for clarity.

Morse tapers (DIN 228)

Morse taper Form A and Form B with end views, reducing sleeve and drift

Taper	Ratio	D mm	d mm	L mm	D in	d in	L in	Form A thread	Form B tang b mm	Form B l1 mm
MT0	1:19.212	9.045	6.40	50.8	0.3561	0.252	2.0000	-	3.9	59.5
MT1	1:20.047	12.065	9.37	54.0	0.4750	0.369	2.1250	M6	5.2	65.5
MT2	1:20.020	17.780	14.53	65.1	0.7000	0.572	2.5625	M10	6.3	80.0
MT3	1:19.922	23.825	19.76	81.0	0.9380	0.778	3.1875	M12	7.9	99.0
MT4	1:19.254	31.267	25.91	103.2	1.2310	1.020	4.0625	M16	11.9	124.0
MT5	1:19.002	44.399	37.47	131.8	1.7480	1.475	5.1875	M20	15.9	156.0
MT6	1:19.180	63.348	53.75	184.1	2.4940	2.116	7.2500	M24	19.0	218.0

D - diameter at the gauge line. d - small end. L - plug depth. Form A: drawbar thread. Form B: tang for a drift. To identify a Morse taper, measure the large end (D).

Drill chuck tapers

Keyed drill chuck with chuck arbor, and a Form A chuck arbor for a mill

Jacobs tapers

Taper	D mm	d mm	L mm	D in	d in	L in
JT0	6.350	5.802	11.11	0.2500	0.22844	0.4375
JT1	9.754	8.469	16.67	0.3840	0.33341	0.6562
JT2	14.199	12.386	22.22	0.5590	0.48764	0.8750
JT2S	13.940	12.386	19.05	0.5488	0.48764	0.7500
JT3	20.599	18.951	30.96	0.8110	0.74610	1.2188
JT33	15.850	14.237	25.40	0.6240	0.56050	1.0000
JT4	28.550	26.345	42.07	1.1240	1.03720	1.6563
JT5	35.890	33.429	47.62	1.4130	1.31610	1.8750
JT6	17.170	15.852	25.40	0.6760	0.62410	1.0000

B tapers (DIN 238)

Taper	D mm	d mm	L mm	Ratio	From
B10	10.094	9.371	14.5	1:20.047	MT1
B12	12.065	11.142	18.5	1:20.047	MT1
B16	15.733	14.534	24.0	1:20.020	MT2
B18	17.780	16.182	32.0	1:20.020	MT2
B22	21.793	19.760	40.5	1:19.922	MT3
B24	23.825	21.290	50.5	1:19.922	MT3

An arbor is named shank first, chuck taper second: MT2 - JT33 = Morse 2 shank with a Jacobs 33 chuck taper. B10/B12 come from MT1, B16/B18 from MT2, B22/B24 from MT3.

7:24 steep tapers

SK 40 holder with pull stud and end view, BT 40 and DIN 2080 holders

Standard	Size	Gauge D mm	Flange mm	Drawbar / pull stud	Notes
DIN 2080	30	31.75	50	M12	Manual drawbar, no V-groove
DIN 2080	40	44.45	63	M16	Manual drawbar, no V-groove
DIN 2080	45	57.15	82.5	M20	Manual drawbar, no V-groove
DIN 2080	50	69.85	97.5	M24	Manual drawbar, no V-groove
SK / DIN 69871	30	31.75	50	M12	V-flange, pull stud (ATC)
SK / DIN 69871	40	44.45	63.55	M16	V-flange, pull stud (ATC)
SK / DIN 69871	45	57.15	82.55	M20	V-flange, pull stud (ATC)
SK / DIN 69871	50	69.85	97.5	M24	V-flange, pull stud (ATC)
BT / MAS 403	30	31.75	46	M12	Thicker flange, pull stud
BT / MAS 403	40	44.45	63	M16	Thicker flange, pull stud
BT / MAS 403	50	69.85	100	M24	Thicker flange, pull stud
CAT / ANSI	40	44.45	63.5	5/8"-11 UNC	Inch pull-stud thread
CAT / ANSI	50	69.85	98.4	1"-8 UNC	Inch pull-stud thread

Milling arbors

R8 arbor, shell mill arbor and horizontal milling arbor

R8 (Bridgeport-type mills)

Taper	Body dia	Taper angle	Drawbar	Key
R8 (Bridgeport)	0.9495" (24.12 mm)	16deg 51min included	7/16"-20 UNF	Keyway in body

Shell mill arbor pilots

Pilot dia mm	Typical cutter dia mm
16	40
22	50 - 63
27	63 - 80
32	80 - 100
40	100 - 125

All 7:24 tapers of one size share the gauge diameter D - the flange, groove and thread tell them apart. SK (DIN 69871) and BT are not interchangeable in an ATC spindle; DIN 2080 holders have no V-groove and use a manual drawbar; CAT uses inch pull-stud threads. Shell mill arbors are named by shank and pilot: SK40 - 27 = SK40 shank, 27 mm pilot. Horizontal milling arbors are sized by arbor diameter (22, 27, 32 mm or 1", 1.1/4") - the cutter bore must match, and the running bush sits in the overarm support.