2 Clarkson Autolock Holders

[Susquatch]

I have two Clarkson Autolock collet holders I need to dump, er sorry sell cheap, er sorry clearance priced. The drawbar is 5/8-11. They have been hanging around for way too long and l have no need for them. I don't have a machine they fit. One has a 1/2" collet in it and the other has a 3/8 collet in it.



PM me an offer before I put them on Kijiji or throw them into my scrap bin and turn them into something more useful to me someday.

 

[Crosche]

Are they a NMTB 30 taper?

 

[Susquatch]

Are they a NMTB 30 taper?

Frankly, I have no idea. How would I tell?

 

[Crosche]

NMTB (Quick Change) Shank​

ANSI B5.18, National Machine Tool Builders' Association, 1927. DIN 2080 / IS 2340, ISO R 290-2583 Also called Quick Change, NMTB, MM, National Standard, American Standard Machine Taper, etc. Units built to the ISO standards are commonly considered interchangeable with ANSI units. However, there are a few differences. (See Tables below). Most (but not all) NMTB shanks are compatible with the corresponding size Erickson Quick-Change Spindles. (See discussion below the tables).

ANSI B5.18 (from Kennametal catalog 7060)

Size​

D1​

D2​

D3​

D4 max​

D5*​

L1​

L2​

L3​

L4​

L5​

L6​

G​

30​

1.250 [31.75]​

0.655 [16.24]​

0.673 [17.09]​

1.380 [35.05]​

1.812 [46.02]​

2.690 [68.33]​

0.810 [20.57]​

0.125 [3.18]​

0.076 [1.93]​

0.344 [8.74]​

0.359 [9.12]​

1/2-13 thread​

40​

1.750 [44.45]​

0.935 [23.75]​

0.984 [25.00]​

1.890 [48.0]​

2.500 [63.5]​

3.690 [93.73]​

1.180 [29.97]​

0.188 [4.78]​

0.076 [1.93]​

0.313 [7.95]​

?​

5/8-11 thread​

50​

2.750 [69.85]​

1.495 [37.97]​

1.545 [39.24]​

2.760 [68.6]​

3.500 [88.9]​

5.000 [127.0]​

1.000 [25.4]​

0.188 [4.78]​

0.141 [3.58]​

0.453 [11.51]​

?​

1-8 thread​

* These are Kennametal dimensions. D5 varies with different mfgs. My Erickson Quick-Change 30 master
can accept up to 1.86" dia flange. Some import NMTB-30 tooling I've seen is as large as 1.96".

ISO R 297-2583 and DIN 2080

Size​

D1​

~​

D3​

D4 max​

D5​

L1​

L2​

~​

L4​

L5​

L6 min​

G​

30​

31.75​

~​

?​

?​

50​

68.39​

?​

~​

1.62​

8​

?​

M12​

DO40​

44.45​

~​

22.63​

50​

63​

93.40​

?​

~​

1.6​

10​

11.0​

M16​

45​

57.15​

~​

?​

?​

80​

106.8​

?​

~​

3.2​

12​

?​

M20​

DT50​

69.85​

~​

34.25​

78​

97.5​

126.8​

25​

~​

3.2​

12​

16.0​

M24​

Size​ D6​ D7​ L7​ L8​ L9​ DO40​ 24.0​ 21.05​ 7.0​ 4.4​ 7.0​ DT50​ 38.00​ ~​ 7.0​ 10​ 7.0​

NMTB Shank Tooling for sale:

NMTB 30 NMTB 40 NMTB 50​

NMTB shank compatibility with Erickson Quick-Change Spindles: The NMTB shank was developed for use in the NMTB spindle which uses a draw bar to pull the shank up into the spindle. Tool flange thickness, distance from the gage line of the taper to the outward face of the flange and the flange diameter are not critical dimensions when used in the NMTB spindle. As a result, these dimensions were not consistent between all manufacturers of NMTB tooling. The Erickson Tool Company developed the Erickson Quick-Change spindle to use the NMTB 30, 40, 45 and 50 tool holders already in existence. The Erickson QC system does not use a draw bar, it uses a quarter turn "locknut" to push and hold the tool taper in the spindle. Two "lips" in the nut push against the outer face of the tool flange. The key dimension (gage distance) that causes some NMTB holders to not work in an Erickson Quick-Change spindle is the distance between the taper gage line and the outer face of the flange (gage distance = L4 + L5 in above tables). Gage distance on some NMTB holders is too large, which does not allow the "lips" in the QC nut to engage the outside face of the flange. The other issue is that the flange diameter (D5) on some NMTB holders (mostly cheaper imports) is too large to fit in the mouth of the Erickson Quick-Change spindle nut. All NMTB holders made by Erickson work fine (they are marked Quick-Change), all Universal Engineering holders work fine and I've read that Kennametal, Collis and Valenite holders work fine (at least the ones made in the last 20 years or so). The compatibility of other holders is in question. However, all is not lost, the flange of the tools that do not work can be ground down a small amount and then they work fine in an Erickson spindle without affecting operation in an NMTB spindle. (See Erickson grinding procedure) The "tail" of the NMTB shank is not required when mounting in an Erickson Quick-Change Spindle. So 30-Taper and 40-Taper tooling, without tail, work fine as long as the flange dimensions are correct. DO40 and DT50 tooling can also be used in Erickson Quick-Change spindles, but you may need to take a bit off the tail "ribs" on some tooling for clearance in the Erickson QC spindle.

 

[Crosche]

They might have some markings or serial numbers which may indicate what they are.

 

[Susquatch]

Nothing I can find. Gimme a bit to look at those charts. Looks like a 10 deg taper.

 

[Susquatch]

Shank tip is 0.993
Taper length (axially) is 3"
Max OD of taper is 1.730 min is 0.970

So I would say that they are NMTB - 40 as all the dimensions line up with that.

 

[Crosche]

Thanks for checking.....it would make sense as 40 tapers are more common than 30's.

 

[Susquatch]

Thanks for checking.....it would make sense as 40 tapers are more common than 30's.

And now I know what they are!

Still, they need to go or they become expensive scrap.

 

[Susquatch]

I should have looked at both instead of just one.

Finely etched on the Taper Stub it says "40 INT" for International Taper. Also says:
Type 5 (or maybe S)
BRPAT (British Patent?)
915713
England

Not sure if that's the same as NMTB, but it sure looks like it.

 

[Tom Kitta]

I have some NMTB 40 Clarkson holders. One is 3/4 and the other I think 1 1/4

They are old stuff from UK. Nice for historical reasons.

They are not too much of a use today. They work for threaded EMs - i.e. you have a thread at the end of an EM that threads into the holder in addition to a collet holding it in. This prevents any pull out.

 

[Tom Kitta]

Actually I may have some more sizes - I would have to check - the holders have collets in them that can be exchanged and collets are of different sizes depending on chuck size.

 

[Susquatch]

They are old stuff from UK. Nice for historical reasons.

Ya, they do look kind of nice in my tool drawer. I almost hate to part with them for that reason alone! But I have an R8 Mill now and I need room for R8 tooling so they should either find a good home or become stock for a project. One or the other.

They work for threaded EMs - i.e. you have a thread at the end of an EM that threads into the holder in addition to a collet holding it in. This prevents any pull out.

Ah, I see! I noticed the bottom thread in one of them and wondered what that was for.

But you remind me that someone else mentioned threaded end mills when I was having a problem with them spinning in a worn out collet - which has since been marked "NFG" and may hit the trash can in the near future because its too hard to turn into anything else !

 

[Tom Kitta]

I would have traded you R8 for it if you were not so far away.

 

[Susquatch]

I would have traded you R8 for it if you were not so far away.

Yes, I would have traded you for R8 too. Seems like an no-brainer. But as usual, shipping is kind of a downer.