Thread: why do people put brakes on their lathes ?

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The main reason for me , as I am currently fitting a brake to my AL-320G is because it has a metric lead screw so when threading an imperial thread you need to keep the half nut engaged, stop and then reverse the lathe back to the start of the thread. If you are threading up to a shoulder, you need to wind your cross slide out and hope the tool bit does not crash into the part. So stopping quicker is an advantage - if you intend to do a lot of screw cutting.
For me, all the lathes where I worked had brakes so I am just used to it.

Blimey that was a quick reply. I tried to delete the post but didnt manage.

I found this thread Lathe Chuck Brake - HomemadeTools.net gives much the same reasons as froglegs.

I did wonder if the brake mechanism could also serve as a retainer to prevent the chuck from unscrewing.

A 10" chuck at 2000rpm takes quite awhile to slow down by bearing friction.

Originally Posted by steamingbill

I did wonder if the brake mechanism could also serve as a retainer to prevent the chuck from unscrewing.

If you were running a lathe with a threaded spindle nose and screw on chucks, face plates etc, and nothing else to lock the chuck to the spindle, a brake system would increase the spindle deceleration, and with a heavy chuck and work in place, with a lot of inertia, might actually cause the chuck and work to start unthreading from the spindle. Of course, having a tailstock center operating to support the far end of the work would prevent the combination from moving more than a degree or so, so it would not unwind in that situation.

One place that I worked bought a $2.5K Osmestore 8 or 10 inch lathe which had a threaded spindle nose and a groove behind the register. Both chucks supplied were drilled and threaded for 'keepers', small brackets that screwed to the chuck boss and engaged in the groove and limited the chuck from unscrewing more than about 10 degrees so the machine could not throw a chuck when running in reverse. An effective if inelegant solution.

Larger braked lathes generally use a different mounting method that locks the chuck etc to the spindle so it cannot rotate on it. Common methods I have come across include camlock systems and keyed and tapered spindles with threaded locking rings as used with Monarchs, some Chipmasters etc