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Repairing a 4 jaw chuck.

Replacing worn out hexagons in screws.

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Brian H07/03/2016 20:12:07
2312 forum posts
112 photos

A 4 jaw chuck came with my Boxford AUD several years ago and, although I have used it a few times it was always unsatisfactory because the jaw screws were badly worn and cracked.

I had a look for new screws only to find them in very short supply and one site that had them wanted £48 each, which is a bit pricey when you need 4 of them.

I decided to drill and tap the screws 3/8" Whit and get some 3/8" whit capscrews.

When they came I was delighted to find that the hexagon was exactly the same as the old ones, though without the wear and cracks.

The capscrews were fastened in with permanent Loctite and I now have a usable chuck at a fraction of the price of new screws.

Not for nothing are we model engineers known as tight!



Martin Connelly08/03/2016 10:57:11
2183 forum posts
227 photos

I have a 4 jaw with cracks around what on my chuck are square recesses in the screws. The rest of the screw is in good condition so there is no problem using it at the moment. If it does start to be a problem it's nice to know there is a solution that is relatively easy and low cost. My suspicion is that the screw on chuck has been fitted or removed by a previous user using a mallet or hammer on the chuck key in the screw hole. Personally I try to avoid putting the chucks on so hard that they require impact forces to remove them.


Ajohnw08/03/2016 13:33:55
3631 forum posts
160 photos

Some people use hex socket cap screws so that they can adjust the work with their fingers initially. Only usually seen on clock sized lathes. Also has the advantage that it's easy to get high tensile ones. Not sure about grub screws.



Phil Whitley08/03/2016 21:49:01
1450 forum posts
147 photos

Excellent repair Brian, and a damned good idea!¬ Must file that away for future use!


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