Jacobs Tapers

Jacobs Taper Dimensions

The Jacobs Taper (abbreviated JT) is commonly used to secure drill press chucks to an arbor.

The taper angles are not consistent varying from 1.41° per side for #0 (and the obscure #2 ¹⁄₂) to 2.33° per side for #2 (and #2 short).

There are also several sizes between #2 and #3: #2 short, #6 and #33.

Taper	Small End	Big End	Length
#0	0.22844 in (5.8024 mm)	0.2500 in (6.3500 mm)	0.43750 in (11.113 mm)
#1	0.33341 in (8.4686 mm)	0.3840 in (9.7536 mm)	0.65625 in (16.669 mm)
#2	0.48764 in (12.386 mm)	0.5590 in (14.199 mm)	0.87500 in (22.225 mm)
#2 Short	0.48764 in (12.386 mm)	0.5488 in (13.940 mm)	0.75000 in (19.050 mm)
#2 ¹⁄₂	0.625 in (15.875 mm)	0.677 in (17.196 mm)	1.055 in (26.797 mm)
#3	0.74610 in (18.951 mm)	0.8110 in (20.599 mm)	1.21875 in (30.956 mm)
#4	1.0372 in (26.345 mm)	1.1240 in (28.550 mm)	1.6563 in (42.070 mm)
#5	1.3161 in (33.429 mm)	1.4130 in (35.890 mm)	1.8750 in (47.625 mm)
#6	0.6241 in (15.852 mm)	0.6760 in (17.170 mm)	1.0000 in (25.400 mm)
#33	0.5605 in (14.237 mm)	0.6240 in (15.850 mm)	1.0000 in (25.400 mm)