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Wednesday, April 14, 2010

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/

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