ER collets - a Haas Automation video worth watching

[Alan H.]

5C collets are held by the taper. They aren't going to unscrew no matter how you apply torque to the collet itself. There's also an anti-rotation pin in the collet, but that's just there to make it easier to install the collet.

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Agree with you but if you reread the string we weren't talking about 5C's backing out. We were talking about an ER chuck that's held in the head's MT with a drawbar and the concern that the chuck could back off the drawbar in reverse.

Here's the ER chuck King linked to above.

 

[pstemari]

...We were talking about an ER chuck that's held in the head's MT with a drawbar and the concern that the chuck could back off the drawbar in reverse...

That's even less likely. Morse tapers are self-holding, much more so than a 5C collet taper.

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[Alan H.]

Again just to be clear, the point of the discussion was that a morse taper lathe chuck needs to be secured with a drawbar.

You cannot ignore the side load on a lathe chuck.

 

[pstemari]

The speculation above was that a drawbar holding an ER collet chuck in a Morse taper could unscrew if you run the lathe backwards.

Assuming the drawbar is tight to begin with, that's not going to happen. The drawbar prevents the Morse taper from being dislodged, and the Morse taper is absorbing the torque load.

FWIW, dislodging a Morse taper with side load is a lot harder than dislodging a Jacobs taper. Every time I've seen a drill chuck get knocked loose, it was the Jacobs taper at issue, not the Morse taper.

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