Possibly stupid question about chucks

[DMI]

I'm picking up an old (1930 ish) lathe at the weekend which needs a bit of work doing to it, I have someone to replace the bits needed so thats not a problem.

But.......I'm going to get a pair of tower jaws made to fit and was wondering if they had locator pins on them to allow the wood to be rotated and still maintain the airway alignment, ie the pins pierce the wood at the airway/bowl junction so they still line up perfectly when you rotate it.

David.

[Massis]

I'm getting mine every day now, but as far as I know, they don't have locator pins on them. I have never even heard of factory made jaws with locator pins... These are mostly custom made jaws I believe...

[DMI]

Well I thought it was a good idea.

[Massis]

You might add some yourself? drill a hole, tap it and add a small screw?

[caskwith]

Adding your own pins would be a fairly simple affair. Clap the tower jaws together and place in a drill press vice, try and get everything set up as accurately as possible. If you don't have a drill press clamp them to the cross slide of your lathe for drilling. Any method that will allow an accurate hole basically. Then tap for a small grub screw which you can grind/turn a point on easily.

[Massis]

I do imagine the tricky part is making sure the pins are in the EXACT center to make sure you pivot your block around the correct point?

[caskwith]

Yes they need to be centred but we are talking about pipes here so accuracy doesn't need to be NASA standard.

[WCannoy]

Yes they need to be centred but we are talking about pipes here so accuracy doesn't need to be NASA standard.

Whoa, whoa, whoa...! What?

[DMI]

I played around with the idea and tried it out on my spare chuck (on a taig c3) and yes it works but:

The pins need to be accurately placed or the block does not rotate evenly and when you tighten the chuck you lose the alignment.

Different sized blocks need the pins to be in different places or you can end up with very little wood in the chuck or the reverse.

I also discovered that my workbench is not as solid as I thought, vvvvviviiibration, a four jaw independent would be better for the job (IMO) and that briar is a bugger to turn, it snatched and bent a chisel.

So a good idea in theory but in practice not so good.

David.