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Logan AC-210 Production Collet Closer


Sep 4, 2023
My 1945 Logan 200 lathe came with a Logan AC-210 Production Collet Closer (see attached). It's a push type that supposedly allows 5/8 through stock but some of the collets that came with the machine go up to 3/4. After fiddling quite a bit, the seller was able to demonstrate that it worked but it's still a mystery to me how it works, despite studying the somewhat blurry cross section drawing. The lever bolts to the bed and has a yoke with two ball bearings that engage a slot in the outer rotor housing. This allows the closer to loosen the collet and advance the stock without stopping the lathe. A rearward force on the housing moves the collet into place. Three internal pawls move the collet sleeve against two small coil springs in the outer housing but they have nowhere near enough force to clamp it tightly. I can see that a steady force on the lever could maintain the clamping force but the geometry doesn't seem to be an overcenter arrangement. Any idea how this works?


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Forgot to attach the cross section and overview


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There are three little pivoted cam levers inside the chuck that lock into position to clamp the collet on the work. You have to adjust something to get the hand lever to operate properly. I am not familiar with that chuck, so I do not know how to adjust it, but it may just be where on the bed you clamp the hand lever support. Look on the chuck for two parts with mating threads and a way to adjust their position once the chuck is on the lathe with a collet inserted.

Maybe one of the Logan lathe instruction books includes instructions for that collet chuck.

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Yes, the levers do lock the collet against the springs and prevent it from moving outward but when you let go of the handle, the only clamping force on the collet appears to be the compression spring force which is quite small. The springs are only there to keep the levers from disengaging. The springs stick out of recessed wells and when they're compressed into the wells, the collet sleeve bottoms against the outer housing and the handle force goes directly through the sleeve to the collet, clamping the work securely. However when the force is removed from the handle, I don't see any mechanism to maintain it. Could it be the friction in the tapered collet itself? That might be the case but I was taught that since friction is tricky to count on, you can still use it in designs but if it helps you, assume a coefficient of zero and if it hurts you, assume a coefficient of 1.