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14x40 tailstock arbor stuck & tuneup

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petertha

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For some reason my lathe tail stock arbor got stuck in the MT quill socket. I’m not certain why because it always ejects when I retract it back below ~ 0.5”. I guessed maybe I wiped it too clean or embedded a chip? It was stuck in there good. I removed the handle & unscrewed the leadscrew so I could see the end of the arbor from the end of the TS casting block. I put a rod in there & tapped it pretty good but still no go. I was worried I might damage something else so I disassembled the TS (for the first time actually). The procedure is: unscrew the lead screw so it un-threads from the quill & detaches internally, remove the double jam nuts, remove the spin handle, remove the ball off the quill lock handle & resting pin so it can unwind from the brass lateral quill lock thingy, drift out the brass thingy. Now the quill will slide out towards the headstock.

Once I had the quill out with the arbor still stuck I wasn’t too worried about drifting it a bit harder. Still no go. So I sprayed some WD-40 in the barrel & heated the quill with my heat gun, some more knocks, then it came. Whew! So no pics of that operation but I thought I’d share some internals in case you run across something similar.
 

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petertha

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The brass clamp, color coordinated cap screws & slightly cleaned up shoe in position before quill insertion. I stoned the slot sides so I did not want to remove material off the sides of the shoe. I cleaned up the nose & chamfered the burrs. Its running smooth now.
 

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petertha

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Am I understanding the tailstock internals correctly?
- big fat chunky strong looking tang on the end of the arbor engages something inside the quill to prevent rotation
- but quill transfers that torque to the tailstock casting via the keyway slot into that little shoe slider part, essentially the cross section of the round pin segment that fits in the casting hole
- so anti-rotation torque basically boils down to shearing that pin plus any 'stiction' force from the MT arbor/socket fit

Maybe its this way by design?
 

petertha

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Answering my own question here. In fact, I probably had this figured out a long time ago & since forgot. There is no anti-rotation mechanism that engages the tang on the end of the MT3 arbor inside the quill barrel. Its just the tapered fit.
 
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