Morse tapers
Morse tapers are self-holding (friction grips them) and are used on drill shanks, lathe tailstocks and drill-press spindles. Measure the largest diameter at the mouth of the socket or the thickest part of the shank, then match it to the gauge diameter.
Morse tapers (ISO 296 / DIN 228)
| Taper | Gauge dia. mm | Gauge dia. in | Taper ratio | Taper per foot (in) | Included angle | Drawbar thread |
|---|
| MT0 | 9.045 | 0.3561 | 1 : 19.212 | 0.6246 | 2° 58' 54" | - |
| MT1 | 12.065 | 0.4750 | 1 : 20.047 | 0.5986 | 2° 51' 27" | M6 |
| MT2 | 17.780 | 0.7000 | 1 : 20.020 | 0.5994 | 2° 51' 41" | M10 |
| MT3 | 23.825 | 0.9380 | 1 : 19.922 | 0.6023 | 2° 52' 31" | M12 |
| MT4 | 31.267 | 1.2310 | 1 : 19.254 | 0.6232 | 2° 58' 30" | M16 |
| MT5 | 44.399 | 1.7480 | 1 : 19.002 | 0.6315 | 3° 00' 52" | M20 |
| MT6 | 63.348 | 2.4940 | 1 : 19.180 | 0.6257 | 2° 59' 12" | M24 |
Form A shanks have a tapped end for a drawbar (thread shown). Form B shanks have a flat tang that is knocked out with a drift. MT0 is normally tang type only.
Drill-chuck tapers
Jacobs drill-chuck tapers
| Jacobs taper | Large end in | Large end mm | Taper per foot (in) | Included angle |
|---|
| JT0 | 0.2500 | 6.35 | 0.59145 | 2° 49' 24" |
| JT1 | 0.3840 | 9.75 | 0.92508 | 4° 24' 53" |
| JT2 | 0.5590 | 14.20 | 0.97861 | 4° 40' 12" |
| JT2 Short | 0.5488 | 13.94 | 0.97861 | 4° 40' 12" |
| JT33 | 0.6240 | 15.85 | 0.76194 | 3° 38' 12" |
| JT6 | 0.6760 | 17.17 | 0.62292 | 2° 58' 25" |
| JT3 | 0.8110 | 20.60 | 0.63898 | 3° 03' 01" |
| JT4 | 1.1240 | 28.55 | 0.62886 | 3° 00' 07" |
| JT5 | 1.4130 | 35.89 | 0.62010 | 2° 57' 36" |
B tapers (DIN 238)
| B taper | Large end mm | Same taper as |
|---|
| B10 | 10.094 | MT1 |
| B12 | 12.065 | MT1 |
| B16 | 15.733 | MT2 |
| B18 | 17.780 | MT2 |
| B22 | 21.793 | MT3 |
| B24 | 23.825 | MT3 |
B tapers are short Morse-derived tapers used on chuck arbors. An arbor is named shank-first, e.g. MT2 – B16 fits an MT2 spindle and a B16 chuck. B12 has the same angle and gauge diameter as MT1 but is shorter.
Milling machine tapers
7:24 steep tapers (ISO 7388 / DIN 69871 / MAS 403 / ANSI B5.50)
| Size | Gauge dia. mm | SK / DIN 69871 pull stud | BT (MAS 403) pull stud | CAT (ANSI) pull stud |
|---|
| 30 | 31.75 | M12 | M12 | 1/2"-13 UNC |
| 40 | 44.45 | M16 | M16 | 5/8"-11 UNC |
| 45 | 57.15 | M20 | M20 | 3/4"-10 UNC |
| 50 | 69.85 | M24 | M24 | 1"-8 UNC |
All 7:24 tapers have an included angle of 16° 35' 39" and are not self-holding: they are located by the taper and driven by keys in the flange. SK, BT and CAT holders of the same number share the gauge diameter but differ in flange shape and pull stud, so they are not interchangeable on an automatic tool changer.
R8 (Bridgeport-type mills)
| Feature | Value |
|---|
| Body diameter | 0.9495" (24.12 mm) |
| Drawbar thread | 7/16"-20 UNF |
| Taper included angle | 16° 51' |
| Location | Keyway in body engages a pin in the spindle |
| Typical capacity | Round collets 1/16" to 3/4" (some sets to 7/8") |
