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Expanding mandrel doe blind hole

Nitrous

Plastic
Joined
Jan 11, 2013
Location
Canada
Expanding mandrel for blind hole

Hi guys,

I'm looking for an off the shelf expanding mandrel that can be used to hold a bottle cap from the inside.
This is for use on a small lathe, without an enormous holding force.
What I envision is an arrangement where the expanding plug is pulled in from the spindle, like a draw bar.

Any thoughts on what I'm looking for ie what I should order? Alternatively, do I need to build something to do the job?

Thanks
Doug
 
Last edited:
Not knowing any particulars I'd say just chuck up yer beer bottle and use it to grip the cap...

Maybe a 5C collet closer and ID collet?
 
I think there are easier ways. For example...

...if you wanted to turn the outer face of the cap, you could create a recess in a 5C style emergency collet, and gently squeeze the flange.

...iif you wanted to turn the "return flange" on the cap, you could create a pilot on a piece of barstock (normal 3-4 jaw chuck) that precisely fits in the cap recess. Then slide the tailstock forward to put clamp the bottle cap on the pilot with the ram. Just like turning between centers, although missing then is another piece of flat or round bar with a 60 degree lathe center hole in it to protect the cap from being pierced by the sharp point of the live or dead center.

All of above are much more easily obtained than a blind expanding internal mandrel IMHO and I would suggest at lower cost too...
 
i would make mandrel same dimension of bottle end. push cap on like the bottler does with a tool mounted in tailstck.
 
Short thread the stub mandrel to match cap and have it bottom out in front, to leave all free to work on, including a rolled flange around the opening if so designed?

3 notched (as threads) fins splayed 120° equadistant through slots into a carrier tube ramped edges inward pressed outward with a matching taper drawbar?

4 slots in a chucked "spring steel" tube with a small bladder inside right end, and rotary air coupling on the tube projecting out the left end of the spindle, ball valve for short through actuation on the stationary side of the rotary coupling?

Edit: correction, 2 way air valve instead of ball valve. Allows a single air line to bladder, pressure and exhaust.
Bob
 

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Thanks guys,
I think this might be the direction.
Ultimately, I'd like to be able to "expand" the metal cap as a shell.
Doug
 








 
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