Drawbar fittings for lathes

[MalcBParticipant @malcb52554]

If the OP Tim dosnt really want to start carving the lathe up, then maybe thinking about using a backplate mounted ER chuck in place of spindle collets would be wise, especially if they havnt hey been purchased.

This would increase the holding capacity down the spindle to practically its I.D. And even larger at the nose for the depth of the collets/chuck.

[Mark CParticipant @markc]

That was another reason for suggesting a threaded bush. You don't need to carve anything up, just think a bit about doing what you want in an elegant simple method. Ega and I are talking specific to milling machines but the principle can just as easily be applied to a lathe. The bush could easily be made with some form of taper locking arrangement perhaps fitting over the end of the spindle. I don't think either of us suggested this was the only way to do it but it was at least a constructive idea rather than assuming it is to complex for the OP to implement.

Mark

[Andy AshParticipant @andyash24902]

I'm not precisely sure what the O.P. is trying to do.

I have an S7 and I hate bashing the drawbar to release taper fittings like collet chucks.

I just got myself a 1" length of 3" dia steel bar and made a protector. I bored out the middle and screw-cut a spindle nose fitment into it. It's just a blank bit of 3" bar that goes onto the spindle nose. You can still stick MT2 fitments through it, but when you need to remove them you can put a pry bar between the protector and the back of the collet chuck, boring head, jacobs chuck or whatever.

Certainly it sometimes releases with quite a ping. Usually I undo the drawbar a couple of turns only, before using a lever to ping it. That way the drawbar catches the attachment rather than it launching into the bed. Once the taper is loose you can just unscrew the drawbar with your fingers.

I never do the protector up more than hand tight. It needs nothing more.

The lever might seem brutal, but if you smash the drawbar and the taper does not release, then the energy is absorbed nowhere else than the bearings.

With the lever, you only apply force to the wedged components.

P.S. You might be tempted to unwind the protector into the back of the MT fitment. I wouldn't recommend it because the thread on the nose isn't up to it. You could make the protector into two parts that screw together. With the protector wound against the register on the spindle nose, the register takes the force. Then you can make your own square or acme thread on the protector which can be used to drive an MT attachment out of the nose.

It's more complicated to make, but the acme or square threaded screw-jack alternative is a better solution.

Edited By Andy Ash on 18/01/2016 22:23:22

[Tim StevensParticipant @timstevens64731]

What the OP (yes, that's me) is trying to do is to compile advice for relative beginners who don't have a lot of kit, yet, but do want to do things without spoiling what they have got. The question was really related to simple direct MT collets, not the more adaptable (and easier to extract after all) ER variety.

Thanks anyway to y'all for an interesting bunch of ideas and suggestions.

Fancy me going over onto two pages – well I never …

Regards, Tim

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