Making a draw bar thread adapter

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Making a draw bar thread adapter

This topic has 9 replies, 7 voices, and was last updated 18 December 2015 at 16:59 by Ketan Swali.

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18 December 2015 at 12:50 #216827
Paul Relf-Davies
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@paulrelf-davies37806
Hi All.

I've acquired a 2MT ER25 collet chuck and collet set (the one ArcEuroTrade sell – the one with the M10 draw bar thread: 050-110-25530) and have been making an adapter to use it with my DW Mk1 mill, which has an M8 draw bar.

I purchased an M10x1.5 die and made my adapter – M10 male to M8 female.

The problem is that the adapter screws very sloppily into the collet holder. If I screw a normal M10 nut onto the adapter, there is no slop, so I guess the thread has been formed ok.

I'm wondering if the draw bar thread in these collet holders is an 'odd' M10 thread pitch. Does anyone know?

cheers

Paul
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18 December 2015 at 12:50 #32614
Paul Relf-Davies
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@paulrelf-davies37806
18 December 2015 at 12:57 #216828
John Rudd
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@johnrudd16576
Try some M10 bolts or studding in the drawbar….is that a slack fit?
18 December 2015 at 13:07 #216829
CotswoldsPhil
Participant
@cotswoldsphil
Hi Paul,

If as John suggests a 10mm bolt or studding is sloppy in the chuck then your option is to screw-cut the external 10mm thread to achieve a close fit.

CP

Edited By CotswoldsPhil on 18/12/2015 13:16:54
18 December 2015 at 13:39 #216834
Paul Relf-Davies
Participant
@paulrelf-davies37806
Thanks both for you replies…

I didn't have a have any M10 studding to hand the other night when I made the adapter, but I think I should be able to lay my hands on an M10 bolt this weekend…(for some reason I have penlty of M8 & M12…but no M10)

Unfortunately, screw cutting a thread that isn't an option, at least not at the moment. My lathe has an imperial lead screw & I don't have the change gears to concoct a metric thread.

P.
18 December 2015 at 14:31 #216846
Tim Stevens
Participant
@timstevens64731
It is likely, I suggest, that the thread in the collet chuck is somewhat oversize. This may be a deliberate ploy in manufacture to avoid problems with distortion during hardening, or it may be (dare I suggest this?) that the manufacturers were careless? As the part affected is likely to be made out of something stronger than cast iron, and as a draw bolt is never tightened as you would a cylinder-head bolt, it is very likely to be strong enough, even if a loose fit.

Regards, Tim
18 December 2015 at 14:50 #216850
Lambton
Participant
@lambton
Paul.

I suggest you try opening up the die a bit to produce a slightly shallower thread. This may help.

Otherwise talk the Keetan at Arc- he is very helpful.
18 December 2015 at 15:43 #216856
John Haine
Participant
@johnhaine32865
"I sn't an option, at least not at the moment. My lathe has an imperial lead screw & I don't have the change gears to concoct a metric thread."

Are you sure? M10 is 17 tpi near enough for it probably not to matter over the length of thread you'll need. Could you cut that with the gears you have?
18 December 2015 at 16:51 #216863
Paul Relf-Davies
Participant
@paulrelf-davies37806
So, I also emailed ArcEuroTrade about this as well as posting here & I have just had a phone call from them to explain the situation.

Apparently the thread in the collet holder is deliberately cut a very little loose, to facilitate unscrewing. The theory is that the holder is being held in the quill by the taper. The draw bar and hence the thread is only there to provide a little security. Indeed, they confirmed that an M10 bolt would also be a little slack in the thread. This seems to make a certain amount of sense… after all would you want to end up with the collet holder and the draw-bar as a single piece, due to a jammed thread…?

To be completely honest, the adapter, as it stands, seems to function exactly as intended. Also I have to say that the customer service I have received from them on this is exemplary.

Cheers & Merry Christmas!

Paul.
18 December 2015 at 16:59 #216864
Ketan Swali
Participant
@ketanswali79440
Posted by Paul Davies on 18/12/2015 12:50:11:

Hi All.

I've acquired a 2MT ER25 collet chuck and collet set (the one ArcEuroTrade sell – the one with the M10 draw bar thread: 050-110-25530) and have been making an adapter to use it with my DW Mk1 mill, which has an M8 draw bar.

I purchased an M10x1.5 die and made my adapter – M10 male to M8 female.

The problem is that the adapter screws very sloppily into the collet holder. If I screw a normal M10 nut onto the adapter, there is no slop, so I guess the thread has been formed ok.

I'm wondering if the draw bar thread in these collet holders is an 'odd' M10 thread pitch. Does anyone know?

cheers

Paul

Paul,

I would suggest that the fit is fine as it is, provided you are using correct drawbar, i.e. metric M10 and not imperial. Do try out an M10 bolt as well as studding, as we have, and we confirm that there is no issue or cause for concern.

I would advise to leave the product alone without trying to modify it in any way. I would suggest that Tim Stevens comments are close to the truth and that if the fit is loose, it may be to avoid problems with distortion during hardening. But it isn't loose as to cause any issue. The drawbar – loose or tight simply holds the MT2 arbor in place to stop it from falling out. The MT2 in itself is a friction fit. If you still have doubts, return the set for a refund. Happy to take it back.

Ketan at ARC.
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