Which Collet Chuck Do I Have

Sorry newbie..!!!! got myself a lover Beaver Mill but need to buy a new Collet Chuck. The manual notes it could be a INT30 or INT40... dose anyone have any mesurements of the two chucks that they can give me so i can work out which one i have?

Looking to buy a ER40 collet set to go with the new chuck, but see that they are M16 size Drawbar so will also need to get a new Drawbar as the one i have i think is a 7/16.

Google int 30/40 specs and you will be spoilt for choice.

This page lists a whole range of machine tapers and is well worth bookmarking:

https://www.tools-n-gizmos.com/specs/Tapers.html

A 30 taper is 1.25 inches major dia.; a 40 taper is 1.75 inches.

Standard drawbar size for 30 taper is 1/2" or 12mm; for 40 taper it is 5/8" or 16mm.

Tooling with an imperial drawbar thread can have either BSW or UNC threads; the thread pitch for 1/2" BSW and 1/2" UNC differs.

AH!

Thank you for that last point!

My Myford mill uses R8 tooling but I wonder if some that I have is actually Whitworth 12tpi rather than Unified 13tpi threaded, hence being more awkward to screw in.

Alternatively, since I had to make a new drawbar (original one lost in a house-move) I may have given it the wrong thread!

Though I think there is a problem inside the spindle, to prevent reliable engaging.

1/2" UNC -s 13tpi, 1/2" BSW is 12tpi. If you are screwing one into another, then one or both threads will be buggered over the length of engagement you should expect for a 30 taper or R8 drawbar thread.

All of my holders for the Beaver are 12mm ISO30 with one 1/2"BSW, I recently aquired a Beaver made horizontal drive, which is original and standard 1/2" UNC NMBT30 thread. So I've got to make a third drawbar. Thinking of making double ended bars with M12 on one end and UNC/BSW on the others, with appropriately threaded nuts for the top ends. That way I'm back to two drawbarsand only need to change the nuts and ends over for the two least used fittings.

Edited By Mark Rand on 26/07/2023 19:25:04

Nigel, R8 stuff can also come with UNF threads

As below your original but above this post, I was under the impression that R8, being invented by Bridgeport was univerally 7/16" - 20 UNF.

I have seen it reported that it is often the fit between the key in the spindle and the keyway in the tool that causes issues. Less than perfect quality tools/collets can have undersize keyways.

Hi DC31k, thanks for your post. As the old Chuck i have has a dimamiter of 44mm (large end) that means its a INT40 ??

The large end of the tapered bit...

To identify the taper, study the charts noted by DC31k. Strangely, INT tapers do not seem to be listed.

If the taper is an INT one, the dimensions will be Imperial, fractions of an inch, not Metric.

The taper is 3.5" per foot.

For an INT 30 , the major diameter will be 1.250" reducing to 0.5625" over a length of 2.625"

Drawbar thread is likely to be BSF, possibly 7/16 or 3/8?

For an INT 40 , the major diameter will be 1.750" reducing to 0.6406" over a length of 3.8125"

Drawbar thread is likely to be BSF, possibly 7/16 or 3/8?

Metric units are unlikely to be exact "round numbers", and so cause you needless hassle.

HTH

Howard

Thanks Howard Lewis....

Also called bt30 or bt40

BT is the same taper, but not the same shape. It's not as long as NMBT.

Pictures and dimensions here:- **LINK**