Bernerd Chuck

[sparky mikeParticipant @sparkymike]

[sparky mikeParticipant @sparkymike]

Hi,

I have a Bernerd 60mm chuck which is used on a watchmakers lathe. If the three screws that hold the jaws in place, are fully tightened the chuck adjustment, which is done by a knurled ring locks up. Should these screws be left a fraction loose, or should the jaws be stoned to prevent the above happening.?

Original Bernerd instructions would be handy if anyone had them.

Edited By sparky mike on 25/04/2013 20:32:56

[Chris TriceParticipant @christrice43267]

I’ve got one of these and like you, I loosen the screws just a tad, grip the subject and then tighten the screws again (if I can get to them). It pulls in everything nice and tight.

Mine doesn’t appear to have seen the use yours has though.

Edited By Chris Trice on 25/04/2013 22:24:45

[sparky mikeParticipant @sparkymike]

Hi Chris,

It seems to me that the milled slot in the jaws needs to be a fraction deeper, or perhaps it has minute burrs on it. I will have to examine it closer.

Re. the picture, I realised after I posted that it needed to be smaller in size, but when I tried to delete it and replace with smaller one I could not seem to fix it.

Any tips here welcome.

Mike.

[RJWParticipant @rjw]

Mike, my Burnerd chuck has exactly the same issue, it is an irritation at times, but I do what Chris does and live with it, but must admit I keep thinking I should sort it out!

If your chuck jaws are the same as mine, the bosses on the back are stepped in to locate on the 'scroll blocks' (for want of a better term), the face at either side of the bosses are polished and locate in shallow channels on the chuck face (just visible in your photo), those channels and the backs of the jaws do get fouled with fine brass and other debris which can cause the jaws to jam, so they need to be kept spotlessly clean!
I mainly use the chuck for rough metal chewing, if I need total accuracy I use collets.

John.

[Chris TriceParticipant @christrice43267]

On one occasion, I very carefully cut shims from cigarette paper to put under the jaws. This was a bit fiddly but worked a treat as I only use the chuck for machining thin pieces with a modest grip.

[speelwerkParticipant @speelwerk]

On the Swiss one I have of the same sizes and design you can tighten the screws fully and still have chuck adjustment without any problem. Niko.

[sparky mikeParticipant @sparkymike]

I have now found that one of the jaws can be fully tightened without the scroll locking up ,so seems like the other two jaws will have to be hand scraped on the flat side of the milled rebate.

Cigarette paper is a good idea also Chris.

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