# Cutting large thread on small lathe?



## SVB (23 Nov 2021)

I have an Axminster/ SEIG SC4 lathe.

I would like to be able to cut a M 33X3.5 mm thread in aluminium. I would like to make a vacuum chuck for my wood turning lathe, so the thread will be to allow it to screw onto the spindle in a piece of aluminium approximately 100 mm diameter.

The maximum pitch thread the lathe can screw-cut with change wheels / lead screw i believe is 3 mm so I don’t think through cutting it direct is an option on this lathe. I do have a tap that is the correct size but given the significant thread depth, I fear probably too ambitious for the lathe? Is there any way I can complete this project on this lathe?

thanks

simon.


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## sploo (23 Nov 2021)

Use the lathe to start the thread manually (i.e get the alignment correct with the tap in the tailstock, get just enough bite into the hole with the tap, then remove tap and stock together, clamp the stock in a vice and finish the thread by hand (presumably with a very large tap holder!).

Alternatively, can you get extra change wheels that might allow the 3.5mm pitch thread?


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## Myfordman (23 Nov 2021)

Could you pick up a small faceplate with the thread ready cut and design your vacuum chuck around that?


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## Bob Chapman (24 Nov 2021)

I designed and built my own vacuum chuck system around some M33 x 3.5 nuts I found online. Details on my old website www.bobchapman.co.uk I can't remember where I bought the nuts but I think its on the website. Look under the 'technical' section. I should add that the website is no longer active (I stopped paying for it a few years ago when I retired, but it still exists). Any problems just pm me.
Bob
Edit: Best not search for nuts I found them under fasteners!


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## Robbo3 (26 Nov 2021)

Simon, I have an M33 nut going spare if you want it. No charge.


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## Sarges Workshop (20 Dec 2021)

screw cut your thread to the nearest pitch nearest the correct pitch to a depth of 1 mm, this will allow the tap to bite. cut as much as you can in the lathe, this will keep it square, but i suspect you will have to finish it on the bench. use parrafin as a lubricant, white spirits works, cold tea if you are desperate. 
good luck Sarge


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