MetalworkingFun Forum

Holding square bar in a 3 jaw chuck.

I thought I would show this, holding square bar using a collet (sort of) in a 3 jaw chuck.

This one is for holding 25mm square bar to bore a 20mm dia. hole.

Just to give an idea of the tube size (“collet”) the I/D is 33.5mm dia. the wall thickness is .100” (2.6mm) which gives an O/D of 38.7mm dia.

The way I make them is I first do the I/D first so the square bar just goes in (with a push), then cut the outside to give a wall thickness between 2.3 to 2.8 mm (.090” - .110”) The wall thickness is important from the fact that if it is too thin it will crush under the force of the jaws. If it is too thick then too much force is required to hold the square bar securely – risk of straining the chuck.
I just cut the slot with a hacksaw.


This one was for holding 10mm square bar to cut a 9mm dia. boss. The wall thickness of the “collet” is .100”


Now obviously it is not as accurate as using a four jaw chuck. But sometimes it doesn’t have to be.

Just remember you are using edges (never the best way) the corners so just check for burrs and such.

A few more – from left to right to hold sq. bar 25mm, 10mm, 20mm



Can be useful for the quick hole or boss.
:)
DaveH

Nice way of doing it, just not for real heavy roughing. Watch for distortion on the side where the jaw has only the clamping tube under it.

Ken,

You're right there, only for light duty stuff, - gentle turning:)

DaveH

That is a handy tip Dave, for when you need to do something like that in a hurry and don't want to take the time to switch chucks on the lathe. I have seen a similar tip elsewhere, where you split a regular hex nut like that to hold a bolt or piece of threaded rod in the chuck without damaging the threads.

Cracking tip Dave

Rob

That's a cool idea Dave,

I can see where that would come in handy!

Thanks for the tip.

Jerry.

What? You take away my perfectly good excuse to buy a new 4-jaw chuck?

My wife better not see this!

(03-04-2012, 12:55 PM)rleete Wrote: [ -> ]What? You take away my perfectly good excuse to buy a new 4-jaw chuck?

My wife better not see this!

No where near as acurate as a four jaw, and light cuts only.

DaveH

No problems with it slipping during the interrupted cut?

(03-05-2012, 05:27 PM)B34VD Wrote: [ -> ]No problems with it slipping during the interrupted cut?

No I haven't (yet) but I do take it easy, light cuts.

DaveH