# M20x1.5 to 1"x8tpi



## Leo (8 Mar 2011)

I was wandering if anyone knew where I could find an adapter for an m20x1.5 spindle on a lathe to a 1"x8tpi Chuck. I have bought a hardly used Elektra beckum ( metabo ) HDM 1000 for 100 euros, but will need an adaptor for it.

Thanks for any info.

Leo


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## dickm (9 Mar 2011)

Tricky one, that. The difference in diameter would only be just enough to accommodate the male and female threads. Would be very surprised if there was anything "off the shelf" to fit, so it's probably a case of finding a friendly engineer.


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## Leo (9 Mar 2011)

Thanks Dick,

I think that's going to be the only way I can go.

Waiting for a reply from Phill Irons first, then, if no joy, off to find an English speaking engineer, not easy over here..............


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## katellwood (9 Mar 2011)

Leo 

I used to have a hdm 1000 and had a backing plate made for a three jaw engineering chuck. If I can dig it out you are more than welcome 

In addition I think I have the original screw on drive


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## Leo (9 Mar 2011)

Katellwood,

That would be fantastic, obviously I would pay for the p&p.etc. if you would do that for me. I will have to think of something to send you, in return........hhhhhhhhhhhhhhhhhmmmmmmmmmmmm eerrrrrrrrrrreeeeeeeeerrrrrrrrrr ????? but what ??


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## NetBlindPaul (9 Mar 2011)

Leo,
One thread on top of another you would have about 0.027", 27 thou (about 0.67mm) between the root of the 1" & the crest of the 20mm!
You'll really need either the adaptor offered above, or an extension effectively!


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## Leo (9 Mar 2011)

Thanks Paul, I thought it was a little, little to have holding a chuck. Is it possible to rethread a chuck ?? Probably a stupid question, but if I don't ask, I'll never know.


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## NetBlindPaul (9 Mar 2011)

Yes you could probably change the thread in the chuck, i.e make bigger, IF you have enough "meat" there.
It is probably soft cast iron.
Don't know the chuck "in person" myself, so i can't comment in detail.


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## Leo (9 Mar 2011)

Thank you very much for the help and information !

Leo


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## CHJ (9 Mar 2011)

Leo, if you have to have an adaptor made, a threaded sleeve bored out and tapped/cut to 20mm dia. x 1,50 mm pitch(ISO metric fine) with a 33 X 3.5mm external thread is a possibility, this could be bonded to your lathe spindle and would give you a standard thread for the European Norm. for chucks and avoid the problems of increased overhang of the normal extender type adaptor.

Unfortunately this made to the required accuracy is likely to cost a fair percentage of your lathe outlay.

Here is an old copy of *Axminsters listing* of standard lathe spindle noses which may be of interest.


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## Leo (9 Mar 2011)

More great info. thank you Chas. !!

I have found that my adapter ( 3/4 x 16tpi ) fits very well into the screw on drive, but the 3/4 x 16tpi chuck will not fit the spindle. My question is this, if it's that close, would it just be easier to rethread the spindle to 3/4 x 16 tpi. Sorry but I know absolutely nothing of these things and live a long way away from decent info. If this is possible, could I buy the thingy and do it myself ?? never done this sort of thing before, but it is not easy to get anything done over here.

Sorry to drag this on so much. !!

Leo


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## NetBlindPaul (9 Mar 2011)

Leo,
Now I AM confused, how have we ended up with a 3/4"x16tpi please?


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## Leo (9 Mar 2011)

Paul,

I am so sorry, I looked through the posts above and realised that I had not mentioned this. I thought that I had !!

You try to help people and they mess you around like this ! My fault totally !!!!!!!!!!!!!!!!

My record power chuck is in fact a vicmark that RP. sold a while ago, ( they told me today ) this had an adapter ( home made, not by me ) to fit onto a 1" x 8tpi. spindle. This was so jammed on that it was impossible to get off, I have got it off after a year of trying...........few. The chuck itself is 3/4 x 16 tpi. I had an old 3/4 x 16 tpi adapter, that I tried on the spindle and in the screw on drive. Did I make any sense at all here ???

This mistake, on my behalf, has confused matters and I am very sorry for that. I am now sat in the corner chastising myself with a wet Kipper.......sorry.


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## 9fingers (9 Mar 2011)

Be careful if you get an adaptor made or try to make one yourself.
It is a turning job that demands accuracy.
The thread is purely a means of holding the chuck onto the mandrel. there should be a plain collar behind the thread which has a precise flat face and an accurate diameter.
It is these two surfaces that are used to ensure that the chuck is mounted concentrically and will run true without wobble or vibration
The adaptor has to pick up on the mandrel register and have its own larger register to fit your chuck/faceplates etc

Bob


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## Leo (9 Mar 2011)

9fingers,

I must admit that my chuck with the adapter on, did not run exactly true, now I understand why, it was home made by someone, not me.

Thank you for the info and advice.

Leo


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## CHJ (9 Mar 2011)

9fingers":38bm85o4 said:


> Be careful if you get an adaptor made or try to make one yourself.
> It is a turning job that demands accuracy.
> The thread is purely a means of holding the chuck onto the mandrel. there should be a plain collar behind the thread which has a precise flat face and an accurate diameter.
> It is these two surfaces that are used to ensure that the chuck is mounted concentrically and will run true without wobble or vibration
> ...



That's why I posted the link to the "standard" nose dimensions Bob,



Leo":38bm85o4 said:


> ...., if it's that close, would it just be easier to rethread the spindle to 3/4 x 16 tpi. ...




It may be possible, 3/4" (19.05mm) is is slightly under 20mm so there is enough diameter, however the thread pitch (16 tpi =1.587mm) is slightly different and there is a mis-match over 1" (25.4 mm) of 1.4mm, almost I metric thread pitch. Over a short distance you might get away with it.

But as Bob has said this needs cutting with accuracy and would need to be done on a metal lathe and not with a hand held Die.

Problems associated with the register collar can often be overcome with a simple slim stepped collar as long as it's a good fit on the existing spindle


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## Leo (9 Mar 2011)

Thank you Chas,

Looks like a bigger job than I expected !!!!!


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## dickm (10 Mar 2011)

Sorry, I'm getting a bit confused here too (doesn't take much at my age  ). What is the "native" thread of the chuck, that is, the thread into which you screwed your adapter? It sounds as if it is larger than 1", and many of the chucks that take inserts have a common thread (it's usually something metric and odd). If it's one of the standard ones (which I'd expect it to be) then it's quite possible there is a commercial adaptor out there to fit it and your 20mm nose.
As others have said, it's a precision job if you need to make an adapter, but I've done one or two for my Mystro, so it's not impossibly difficult if you have access to a metal lathe, or know someone who has and can drive it well.


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## Leo (10 Mar 2011)

Hi Dick,

The native thread is 3/4 x 16 tpi. and the adapter is 1" x 8 tpi. so I could use two adapters I suppose, if it came to it.

Leo


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## NetBlindPaul (10 Mar 2011)

Leo,
So the chuck has a 3/4" x 16 tpi male thread?
The lathe has an M20 x 1.5mm female thread?


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## 9fingers (10 Mar 2011)

This thread has got to be a contender for having the most wrong ended sticks for folk to grab hold of - ever! :lol: :roll: 

Bob


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## NetBlindPaul (10 Mar 2011)

Quite!


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## Leo (10 Mar 2011)

Hi Paul,

No the chuck has a female thread and the lathe has a male, sticky out spindle thread...............oh I do confuse things, must be my age.

But the sizes are correct chuck 3/4.............lathe 20mm..........

Leo


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## 9fingers (10 Mar 2011)

OK the two sizes are so close that either an adaptor will have to extend the position of the chuck away from the bearing - highly undesirable
or the back of the chuck (or its backplate) will have the be bored out to larger thread say about 1.25" to allow room for an adapter to screw inside the chuck to keep the over hang to the minimum.

Bob

Thinks! or a new backplate if your chuck has a removable backplate.


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## Leo (10 Mar 2011)

I see what you mean 9fingers,

It looks like a made up adapter or backplate then.

Leo


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## NetBlindPaul (10 Mar 2011)

As per 9 fingers above.
You could however, get this done cheaper perhaps by getting the chuck set up in a metal lathe and bored out and threaded with a large as 9f says say 1.25" then an adaptor screwed in and "glued" & screwed/pinned into place then threaded 20mm x 1.5mm?
However, IF the back plate can be changed then this could be the best option?
Careful though as running accuracy is important with a lathe chuck.


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## Leo (10 Mar 2011)

Thank you all very much for the information and advice.

I started this post without a single clue about what could be done, THEN I MESSED UP THE SIZES, SORRY.

Now I have a much better idea of what to do and thank you all for your patients with me, being a bit dim on the subject.


Leo


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## 9fingers (10 Mar 2011)

You can get a M20 x 1.5 tap here http://www.tracytools.com/index.php?rou ... uct_id=373

which might help a local engineer with a lathe, complete the job for you if he is not experienced in thread cutting on the lathe.

Bob


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## NetBlindPaul (10 Mar 2011)

Shame really I have one & a circular split die!
Also probably a 3/4" x 16 UNF tap & circular split die too!


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## CHJ (10 Mar 2011)

All the options of having spindle nose adaptor or chuck body modified to fit the lathe are going to cost the OP almost as much as he acquired the lathe for unless he can locate a very friendly metal turner.
And unless the spindle nose dimensions are measured reasonably accurately, micrometer preferred not casual calipers, the turner is going to want access to the spindle nose for fit comparison. I certainly could not guarantee a decent fit without either.

I personally would go for a 33 X 3.5 adaptor on the end of the spindle if it was in my shop, that would fit without any undue overhang if any at all.
Then any standard 33mm chucks and accessories would fit, but as I said between material cost and turners time producing a dummy male thread for testing fit and turning the adaptor itself (you could be looking at best part of a days labour for a one of item) it would not be cheap.


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## Leo (10 Mar 2011)

Lots of options, so now all I need to do is find an English speaking engineer, not an easy task here, but I should be better at Spanish.

Thanks all again.

Leo


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## dickm (13 Mar 2011)

Thinking about this some more, from my experience, it's much easier for an amateur to re-thread the actual chuck body than to make an adaptor. The chuck body can be accurately centred in a four-jaw (independent jaw) chuck to bore out and cut the new thread, whereas making an adaptor really needs a special arbour threaded to the "new" internal thread, and there are two threads and two mating surfaces to get spot on. If there is any doubt about the concentricity of the outside of the chuck and the jaws, it's possible to line up with the jaws using a dummy piece held in the morse taper of the metalworking lathe.

Just another two penn'orth!


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## Leo (16 Mar 2011)

After much reading of the advice above, gratefully received, but not too many engineers etc. over here, so..........

I ground down the spindle, after MUCH thinkin' and deliberation with meself, until the inside of my adapter fitted perfectly and ran true, I used the side of a grinding wheel on it, with the Lathe running, for trueness. Glued it on and drilled all the way through and added a bolt, ground the bolt head down.

Seems perfect to me now, but was a scary time........few never again !!!!!!!!!!! Hopefully it won't come loose !!!!!!!!!!! 

Not a recommended method by any means, but here you have to do most things by yourself !! 

Thank you all again for the tips, it may not look like it, but it helped point out the important connections etc. in my mind !!!!

Happy turnin'


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## dickm (17 Mar 2011)

Well done that man! 
As you say, a scary process, but if you are happy with the result, that's all that matters.

Now how long before you get really keen and bore out the nose for a morse taper??????


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## Leo (18 Mar 2011)

Only about another 20 years or so, Dick. 

this scared me to death, I thought that I was going to ruin a new lathe, but didn't ffffffffffeeeeeeeeeeeeeewwwwwwwwwwwwweeeeeeeeeeeeee !!!!


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