Machine taper

Morse

Morse Taper #2 (MT2)

The Morse Taper was invented by Stephen A. Morse (also the inventor of the twist drill) in the mid-1860s.^[1] Since then it has evolved to encompass smaller and larger sizes and has been adopted as a standard by numerous organizations, including the International Organization for Standardization (ISO) as ISO 296 and the German Institute for Standardization (DIN) as DIN 228-1.

Sizes

Morse Tapers come in eight sizes identified by number between 0 and 7. Often this is abbreviated as MT followed by a digit, for example a Morse taper number 4 would be MT4. The MT2 taper is the size most often found in drill presses up to 1/2" capacity.

End types

Morse tapers can have three types of ends:

• tang (illustrated) to facilitate removal with a drift
• threaded to be held in place with a drawbar
• flat (no tang or threaded section)

The taper itself is roughly 5/8" per foot, but exact ratios and dimensions for the various sizes of tang type tapers are given below.

Dimensions

Morse Taper dimensions (mm)

Morse Taper number	Taper	A	B (max)	C (max)	D (max)	E (max)	F	G	H	J	K
0	19.212:1	9.045	56.5	59.5	10.5	6	4	1	3	3.9	1° 29' 27"
1	20.047:1	12.065	62	65.5	13.5	8.7	5	1.2	3.5	5.2	1° 25' 43"
2	20.020:1	17.780	75	80	16	13.5	6	1.6	5	6.3	1° 25' 50"
3	19.922:1	23.825	94	99	20	18.5	7	2	5	7.9	1° 26' 16"
4	19.254:1	31.267	117.5	124	24	24.5	8	2.5	6.5	11.9	1° 29' 15"
5	19.002:1	44.399	149.5	156	29	35.7	10	3	6.5	15.9	1° 30' 26"
6	19.180:1	63.348	210	218	40	51	13	4	8	19	1° 29' 36"
7	19.231:1	83.058	285.75	294.1	34.9	-	-	19.05	-	19	1° 29' 22"

Brown & Sharpe

Brown & Sharpe tapers, standardized by the eponymous company, are an alternative to the more-commonly seen Morse taper. Like the Morse, these have a series of sizes, from 1 to 18, with 7, 9 and 11 being the most common. Actual taper on these is within a close range of .500" per foot.

Size	Lg. Dia.	Sm. Dia.	Length	Taper/Ft
1	0.2392	0.2000	0.94	0.5020
2	0.2997	0.2500	1.19	0.5020
3	0.3753	0.3125	1.50	0.5020
4	0.4207	0.3500	1.69	0.5024
5	0.5388	0.4500	2.13	0.5016
6	0.5996	0.5000	2.38	0.5033
7	0.7201	0.6000	2.88	0.5010
8	0.8987	0.7500	3.56	0.5010
9	1.0775	0.9001	4.25	0.5009
10	1.2597	1.0447	5.00	0.5161
11	1.4978	1.2500	5.94	0.5010
12	1.7968	1.5001	7.13	0.4997
13	2.0731	1.7501	7.75	0.5002
14	2.3438	2.0000	8.25	05000
15	2.6146	2.2500	8.75	0.5000
16	2.8854	2.5000	9.25	0.5000
17	3.1563	2.7500	9.75	0.5000
18	3.4271	3.0000	10.25	0.5000

R8

collets with R8 taper

This taper was designed by Bridgeport Machines, Inc. for use in their milling machines. It is used with a drawbar extending up through the spindle to the top of the machine to prevent the collet from falling from the spindle when lateral forces are encountered. The collet, which is inserted into the taper, has a precision hole in one end for holding a cutting tool and is threaded for a drawbar on other end. They are also keyed (see image) to prevent rotation during insertion and removal. However, cutting torques are transferred through friction at the taper, not through the key. The drawbar thread is typically 7/16"-20tpi (UNF).

The cutting tool is placed in the collet, the collet placed into the taper, and the drawbar is tightened into the top of the collet from above the spindle. The collet has a groove to engage a key in the spindle to keep the collet from spinning inside the taper and to aid in the installation and removal of the collet. The angle of the cone is typically 16 degrees and 51 minutes (i.e. 16.85 degrees) with an OD of 1.25" (source, Bridgeport Manufacturer).

Jacobs

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

Taper	Small End		Big End		Length
	mm	inch	mm	inch	mm	inch
0	5.80	0.2284	6.35	0.2500	11.11	0.4375
1	8.47	0.3334	9.75	0.3840	16.67	0.6563
2	12.39	0.4876	14.20	0.5590	22.23	0.8750
2 Short	12.39	0.4876	13.94	0.5488	19.05	0.7500
2 1/2	15.88	0.625	17.20	0.677	26.80	1.055
3	18.95	0.7461	20.60	0.8110	30.96	1.2188
4	26.34	1.0372	28.55	1.1240	42.07	1.6563
5	33.43	1.3161	35.89	1.4130	47.63	1.8750
6	15.85	0.6241	17.17	0.6760	25.40	1.0000
33	14.23	0.5604	15.85	0.6240	25.40	1.0000

Jarno

Jarno tapers range from a Number 2 to a Number 20. The diameter of the big end in inches is always the taper size divided by 8, the small end is always the taper size divided by 10 and the length is the taper size divided by 2. For example a Jarno #7 measures 0.875" (7/8) across the big end. The small end measures 0.700" (7/10) and the length is 3.5" (7/2).

The system was invented by Oscar J. Beale of Brown & Sharpe.

[NMTB Tapers

The National Machine Tool Builders Association (now called the Association for Manufacturing Technology) in the USA laid down standards for machine tool design, among other things: the taper used on CNC (Computer Numerically Controlled) milling machines.

The taper is variously referred to as NMTB, NMT or NT. Essentially this defines a taper of 3.500 inches per foot or 16.7112 degrees. All NMTB Tooling has this taper but the tooling comes in different sizes. NMTB-25, 30, 35, 40, 45, 50 and 60. With the 40 taper being the most common by far.

CAT and BT tooling use this same taper.

The goal of the taper is to allow a quick and easy change between different tools (either automatically or by hand) and still keep it tight and centered while using it. The spindle on the machine tool is built with a female taper and drawbar. Each individual tool must be fitted with a male taper and the proper adapter for the drawbar.

From http://wikipedia.com/