Headstock thread adaptor.

[Trefor]

Hello.

I have a Coronet Elf lathe with a 3/4" 16tpi thread.

I have acquired a used 3.75" chuck with no indication of the manufacture's name. It has a standard M33 thread and an M33 3.5 to 1" 8 tpi adaptor. So I'm looking for adaptor so that it will fit my 3/4" headstock.

The start of the thread in the M33 chuck is resessed in by about 18mm. I have found an M33 to 3/4" adaptor on the internet, which only has a M33 thread length of 22.5mm then a has "nut", so only going to engage the thread in the chuck by a few mm, which isn't at all good.

Is it possible to buy an adaptor with a longer thread?

Is there a 1" 8tpi to 3/4" 16tpi adaptor or is running with 2 adaptors not recommended?

Any other ideas?

Give up and buy a chuck with the correct thread?

Thanks Trefor

 

[ChaiLatte]

The recessed part of the M33 thread is known as a 'register'.

Hacksaw it off just a little above the first thread. Then the hex adaptor will fit.

Shorten the register to the same dimension as above, but using a slightly more civilised method of someone else's metal lathe.

Removing it will reduce the overhang of the chuck from the spindle and increase rigidity.

What diameter is the register?

Chop the corners of the hexagon adaptor off and reduce the A/F dimension so it fits within the register. That will increase the thread engagement. This could be done with it mounted to your own lathe using a coarse file. You would need to check that the back of the chuck does not hit the headstock.

 

[Distinterior]

This one looks like it may fit.....It has a longer "register "......

https://www.beaufortink.co.uk/spind...indle-thread-adaptor-3-4-x-16tpi-to-m33-x-3-5

 

[Trefor]

The recessed part of the M33 thread is known as a 'register'.

Hacksaw it off just a little above the first thread. Then the hex adaptor will fit.

Shorten the register to the same dimension as above, but using a slightly more civilised method of someone else's metal lathe.

Removing it will reduce the overhang of the chuck from the spindle and increase rigidity.

What diameter is the register?

Chop the corners of the hexagon adaptor off and reduce the A/F dimension so it fits within the register. That will increase the thread engagement. This could be done with it mounted to your own lathe using a coarse file. You would need to check that the back of the chuck does not hit the headstock.

 

[dickm]

Find a guy with a metalworking lathe and ask them very nicely to make one. I've made several, but just no time now.

 

[Trefor]

The register is 34mm in diameter and 18mm deep.

 

[Trefor]

This one looks like it may fit.....It has a longer "register "......

https://www.beaufortink.co.uk/spind...indle-thread-adaptor-3-4-x-16tpi-to-m33-x-3-5

Ooo. Good find, good find. Thanks.

 

[Sachakins]

https://www.ockenden-timber.co.uk/w...-adapter-insert-34-x-16tpi-to-m33-x-35-p-2908
https://charnwood.net/product/thread-adaptor-insert-3-4-x-16tpi-to-m33-x-3-5mm/
https://www.machinery4wood.co.uk/Ch...gAb-RRnDgzGw2IbqMWapUn1cD3bGOY1hoC50AQAvD_BwE
https://www.wigleydiy.co.uk/cnw-insert-3-4-x-16tpi-4464941

 

[Trefor]

This one looks like it may fit.....It has a longer "register "......

https://www.beaufortink.co.uk/spind...indle-thread-adaptor-3-4-x-16tpi-to-m33-x-3-5

Ooo. Good find, good find. Thanks

https://www.ockenden-timber.co.uk/w...-adapter-insert-34-x-16tpi-to-m33-x-35-p-2908
https://charnwood.net/product/thread-adaptor-insert-3-4-x-16tpi-to-m33-x-3-5mm/
https://www.machinery4wood.co.uk/Ch...gAb-RRnDgzGw2IbqMWapUn1cD3bGOY1hoC50AQAvD_BwE
https://www.wigleydiy.co.uk/cnw-insert-3-4-x-16tpi-4464941

Excellent, thanks.

 

[Trefor]

I bought the Charnwood adaptor and it works a treat.
Thanks for the help.