Draw bar thread size for a 2 MT Clarkson autolock milling chuck?

[Antony PriceParticipant @antonyprice56876]

Hi

Is anybody able to confirm the draw bar thread size for a 2MT Clarkson autolock milling chuck? I think it might be 5/16 BSF, but when I try a bolt of that thread it only goes in a few turns. It is possible the previous owner has damaged the thread, but before I re-cut it, I would appreciate confirmation that it is 5/16 BSF

Many thanks

Tony

[Antony PriceParticipant @antonyprice56876]

[Keith LongParticipant @keithlong89920]

Looking at morse taper tooling on sale the standard drawbar thread on 2MT seems to be 3/8 BSW or M10. Possible that Clarkson used a fine thread but I'd have thought they'd have gone with the normal standard. If the previous owner has modded the thread either intentionally or by accident then all bets are off.

Edited By Keith Long on 25/08/2015 15:26:05

[duncan webster 1Participant @duncanwebster1]

Mine is 3/8" BSW

[peak4Participant @peak4]

Posted by duncan webster on 25/08/2015 15:14:56:

Mine is 3/8" BSW

As is mine

[John HaineParticipant @johnhaine32865]

Imperial mt2 tooling all seems to use 3/8 bsw. Standard studding is perfect to make a drawbar.

[RobboParticipant @robbo]

3/8"BSW if Imperial, M10 if Metric

[S.D.L.Participant @s-d-l]

Posted by Robbo on 26/08/2015 09:50:26:

3/8"BSW if Imperial, M10 if Metric

And some will be UNC

Steve

[Ian S CParticipant @iansc]

3/8" BSW, some will be 3/8" UNC, these are both the same pitch, only the thread angle differs, the UNC being 60*.

Ian S C

[BazyleParticipant @bazyle]

Screw a piece of paper/wood/plasticine down it to pick up and measure the thread pitch and the core diameter. At least you have the tool to try things on.

[Mike PooleParticipant @mikepoole82104]

The drawbar thread is often etched on the body of genuine Clarkson holders, can be hard to find and read though! If it is metric it usually has a groove machined at the drawbar end

Mike

Edited By Michael Poole on 26/08/2015 15:19:58

Edited By Michael Poole on 26/08/2015 15:22:16

Edited By Michael Poole on 26/08/2015 15:22:40

[RobboParticipant @robbo]

"The drawbar thread is often etched on the body of genuine Clarkson holders"

Like this one:-

Edited By Robbo on 26/08/2015 19:04:23

[Antony PriceParticipant @antonyprice56876]

Many thanks for the responses to my original enquiry. I’ve managed to get back into the workshop today. I’ve attached a photo of both my 2 MT Clarkson auto lock milling chucks. The one on the left is an “S” type. The “S” type is 3/8 BSW. The “unknown ” has CS 7174 etched on the body. Using a drill bit I’ve measured the “core” of the unknown thread, and arrived at 17/64” (0.2656&rdquo ie a 5/16” thread It is not BSF as I first thought (I couldn’t get a BSW bolt to go more than a thread) . Having looked closely, through a magnifier , I found and picked out the damaged thread. I can now get a BSW tap to go the full length of the thread. I’ve just ordered some 5/16 BSW threaded bar!

Tony

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