Clamp /Latch for screw on chucks.

[Andrew TinsleyParticipant @andrewtinsley63637]

I have come across several mentions of a clamp to prevent a screw on chuck becoming loose when run in reverse.

I was looking at my screw on chucks yesterday and wondered how this clamp/latch was implemented, as I could not see an obvious solution to the above. Can anyone enlighten me as to how such a clamp works?

Andrew.

[Howard LewisParticipant @howardlewis46836]

On my BL12-24 (and presumably their look alikes, Warco BH600, Chester Craftsman etc) behind the regicster is flange. On the back of the chuck is an extension with two diametrically opposed M8 tappings.

These are used to secure two dogs which hook behind the flange, so that IF the chuck tried to unscrew, the dogs would prevent any forward movement.

Retrofitting something like this for a Myford, or similar lathes, might be more difficult, but worth exploring.

I would not be keen on just using a grubscrew, because of the risk of danage to the thread or register, but a setscrew with a plain end, inro a shallow drilling, might be effective.

When I had a ML7, I did not have a problem with chucks coming loose when reverse running (But being aware of the risk was careful) Lathes with heavy braking facilities, can cause this sort of problem.

(Not long ago, I read of someone saying that he had a chuck land in his lap! Fortunately, from a small lathe)

Howard

[John HaineParticipant @johnhaine32865]

On the big bore Super 7 (and maybe the others) there is a vee-groove on the OD of the spindle register between the thread and the flange as in the photo.  A set screw in any backplates etc can engage in this to prevent unscrewing.  IIRC the instructions are NOT to fully tighten this as it may throw the chuck etc off concentric – it is only to prevent the accessory unscrewing, not to allow machining in reverse.

[John Haine]

On John Haine Said:

[…] IIRC the instructions are NOT to fully tighten this […]

That’s an interesting subtlety, of which I was previously unaware John … thanks for mentioning it.

It effectively means that there is no pressure on the safety mechanism unless and until it is needed … very clever!

MichaelG.

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