Thread Size

A bit of a shot in the dark.

Can anyone, offhand, tell me the size of the internal drawbar thread in a Clarkson 30INT chuck please? I have to make the drawbar for the mill to secure the chuck.

Thanks
Jack

Probably 3/8" x 16 tpi BSW, but I have a 3MT one which is 1/2" x 12 tpi BSW..

I thought "I'll look in the Operators Handbook" - full of info, but just says "standard tapping" for the drawbar thread!

No it doesn't say what a standard tapping is!

Hi Jack, it's probably M12 or 3/8 BSW - such chucks available with either thread. Try an M12 screw in it and see if it fits.

Neil

It is either M12 or 1/2 inch x 13tpi (UNC as it is not a British invention)  depending on age and nationality. So best to make it double ended.

Int 40 is M16 or 5/8

Int 20 takes the same size as Int 30 though my sample might be INT 25.

Edited By Bazyle on 24/11/2014 11:11:27

Owing to the confilcting advice I should just clarify - I have double checked my drill chuck, Clarkson chuck copy, and MT2 adaptor are all M12. My original drawbar that I obviously don't use is 1/2x13 and is the machine's 40 yr old original. So I would go with the metric and if you turn up an American holder by mistake you might be able to offload it on me.

Be aware that you might encounter some home made arbors that are smaller made by skinflints.

Check out Arc Euro for INT30 & 40. His adaptors are cheaper than Ebay starting prices.

My older INT40 tooling is definitely 5/8" BSW, not UNC, just to confuse this issue.

Andrew

Jack,

With so many choices offered ... I would suggest just screwing a piece of wooden dowel into the female thread; then unscrew it and measure the tpi or the metric pitch from the imprint.

MichaelG.

Just try a few likely looking screws, take it down to a bolt shop if you don't have any.

Some of the 40 international where unc or unf I think!,

.

I have a Int 30 fitting on my Boxford mill. It's a standard M12 course.

Edit :- What mill have you got Jack

Nick

Edited By Nick_G on 24/11/2014 16:03:43

I have seen M10, 3/8 BSW, 3/8 UNC, M12 and 1/2 BSW, and I expect there was 1/2 UNC as well. I brought some threaded rod back from the U.S. for the UNC one.

Try some bolts or if very carful some Taps to try them.

A lot of auto locks have the size in very feint writing on the side, if tarnished try cleaning up wit a bit of WD40 and fine scotchbrite.

Steve

An AEW Viceroy Horizon, Nick

Horizontal at 25 - 2039 revs, with lots of cutters
But also a vertical head with the aforementioned Clarkson chuck (sans drawbar) with 4 collets from 1/4" -- 3/4" and a selection of cutters. And a hefty vice (with no handle) A genuine ex school machine. Absolutely filthy with muck/oil and grease. but no play on X, Y or Z. And it has cleaned up beautifully. Under 6'-00" tall and only a 25" square footprint. So ideal for my workshop. But it does have a 36" x 8" bed.

The drawbar and vice handles are the first jobs to be done.

Edited By Jack Foreman 1 on 24/11/2014 18:50:37

Edited By Jack Foreman 1 on 24/11/2014 18:50:54

Wow. Thank you all for your input. Varied and interesting too. Much appreciated.
I never envisaged that there would be so much variety.

By a process of elimination I have found it to be a 1/2" x 12tpi BSW thread. I found a 1/2" x 13tpi thread which bound up at 3.1/2 turns, so I tried a 12tpi thread gauge and it appeared to fit. Then I found a 1/2" x 12tpi BSW plug tap and it was perfect. And, miraculously, I also found the 1/2" x 12tpi BSW die, to go with it.

So tomorrow, I will make the drawbar and the vice handle.

Once again, many thanks.
(oh, I got my ticket for Sandown Park today too. I'll see some of you there, no doubt.)

I made my draw bar by getting two bolts from the junk box, cut the heads off, and weld them together.

Ian S C

Drawbar is made. Complete with a brass compression washer
Also the ball bearing race for truing pieces up in the chuck.
The vice handle is next ~ but it's a bit cold in the workshop today. So I may set up a heater tomorrow and do it then.

Edited By Jack Foreman 1 on 25/11/2014 14:59:57

I plumbed in a radiator into mine. But it joins the house so was quite a simple job to put one 'back to back' with one inside the house.

What I wish for though is a wood burning stove in mine. Just not got the space though. - It is however probably best as if I had one I would just sit in front of it watching the flickering flames, drinking tea and contemplating the world with a contented smile. .......................... i.e. little work would ever be done.!

Nick

I do have a couple of very old Baxi Brazillia gas heaters in my workshop. But it is three years since I last used them, And I'm reluctant to take the risk of blowing myself to kingdom come, before I've had a chance to really become familiar with the new mill.