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[edit] Milling Machine Tapers

Parent page is Machining

There are really only a few tapers in common use even with all the names for milling machine tapers. Quite a few manual milling machines use the "R-8" taper, but most CNC and large machines use something else. A tool-holder consists of 2 sections separated by the gage line (the gage line is an imaginary line marking the portion of the tool-holder that matches the bottom edge of the machine spindle). The taper fits into the spindle allowing the machine spindle to transfer rotary motion to the tool holder which holds the tool.

A toolholder has a 2 part specification, taper and tool. This page covers the machine-to-toolholder standard and not the holder-to-tool standard. and example might help. A NMTB #30 collet chuck and an NMTB 1/2" endmill holder fit the same machine, but hold different tools.

The NMTB refers to the taper standard family - the #30 the shank size (if they leave off the #30 part it is assumed to be the small one.) At the end of the tool-holder name is the name of the tool type - 1/2" end-mill holder or

Conversely, a NMTB 1/2" end-mill tool-holder and a Universal Kwik-Switch 200 1/2" end-mill tool-holder will hold the same tool, but fit different machines. The drawings below show only the taper portion of the tool-holder.

[edit] Spindle Size Number

The ANSI standard size is determined by the machine size; Larger machines use larger shanks.

All of the major tapers, except the Universal Kwik-Switch family, use the 3 1/2" in 12" model of the NMTB or 7:24. A 3/8" end-mill #50 NMTB tool-holder is about a serious 9 pounds of metal compared to dainty 3/4 of a pound for a #30 NMTB 1/4" end-mill tool-holder.

[edit] Tool-Holder Tapers

[edit] Universal Kwik-Switch

A Tool-Holders with Ears!

This taper style is also made by Collis who call it Rapid-Switch. The Kwik-Switch is supplied as alternative tooling in Bridgeport, Wells index, and other machines. The 200 series is pretty much equivalent to the NMTB #30, but has more mass and a more positive lock.

Kwik-Switch Size A B C E F H J K L M 100 .875 1.44 0.16 0.312 0.250 1.12 1.56 0.375 1.06 0.68 200 1.312 2.50 0.22 0.375 0.312 1.75 2.12 0.500 1.68 0.97 300 1.625 2.94 0.28 0.438 0.375 2.00 2.50 0.500 1.94 1.22 400 2.250 3.62 0.34 0.500 0.438 2.81 3.25 0.625 2.75 1.75

[edit] Tool-Holders with Collars or Flanges

[edit] Single Flange Tool-Holders

The single collar taper is the most popular, as evidenced by the numerous names it has. Most often NMTB or Erickson Quick Change. NMTB (from National Machine Tool Builders' Association, 1927. and also known as DIN 2080 / IS 2340 SHANK) You'll see it called Quick Change, NMTB, MM, National Standard, American Standard Machine Taper, ISOXX, & QCXX... The American Standard Steep Machine Taper (ASA B5.10-1963) defines 12 tapers: #5, #10, #15, #20, #25, #30, #35, #40, #45, #50, #55, #60. Those numbers in bold are the "Preferred Series" while the others are in the "Intermediate Series". ANSI mentions six taper shank sizes including #30, #35, #40, #45, #50, and #60. For all the sizes the taper is 3 1/2" per foot.

Shank Slot A B C 30 16.1 [.634] 31.75 [1.250] 68.4 [2.75] 1/2-13 40 16.1 [.634] 44.45 [1.750] 93.4 [3.75] 5/8-11 50 25.7 [1.012] 69.85 [2.750] 126.8 [5.12] 1-8

[edit] Dual Flange Tool-Holders

There are two common dual flange types: V-flange (often referred to as Caterpillar V-flanges) and BT-flange.

[edit] BT-Flange and ISO-Flange

[edit] Caterpillar V-flanges

Caterpillar V-flanges use inch threads for the retention knob and are used to hold inch-dimensioned cutting tools. You'll see the CAT flange referred to as DIN69871 I've seen them most often referred to as CAT-30, CAT-40, CAT-45, and CAT-50 and CAT-40 seems to be the most common.

SHANK SIZE A GAGE LINE B C D V30 1.250 1.812 1.875 1/2-13 V40 1.750 2.500 2.687 5/8-11 V45 2.250 3.250 3.250 3/4-10 V50 2.750 3.875 4.000 1-8 [Inches]

[edit] DIN 69871-A TAPER

Need information on this one...

MODEL D1 D2 t1 t2 L1 L2 L3 d1 d2 M max G 25 ? ? 15.9 3.2 ? ? ? ? ? ? ? 50 44.30 47.8 15.9 3.2 33.5 24 31.75 13 45 M12 40 63.55 56.25 15.9 3.2 68.4 42.5 32 44.45 17 50 M16 50 97.5 91.25 15.9 3.2 101.75 61.5 47 69.85 25 80 M24

[edit] R8, R-8 or M1TR taper -- Common Bridgeport Tapered Draw-Bar

This is not truly a taper as defined by Machinery's Handbook, since it is held in place by a drawbar. Picture a long 7/16"NF bolt leading down through the spindle, threading onto the R-8 tool-holder. The included angle is 8.25°1 OD of 1.25" 18.85/2 degrees or 8.25?? Taper = 16 Deg 51 Min.Included End Dia. .9495 +0 -.0003 Overall from front dia. of 1 1/4"is 4" Undercut dia. 15/16" The "arctan(3.5/12)" solution by definition implies a right triangle with a 3.5" short side and 12" long side. Thus, the hypotenuse is 1.25".

[edit] Machine Taper Dimensions table - Morse - Brown & Sharp - Jarno - Jacobs

Parent page is Machining