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plunger
03-05-2017, 04:48 AM
This was asked by someone else and I am curious to know how to do it.
If you need to machine a hexagonal bar of 35mm diameter and the bar is 4meters long,how do you support the outboard piece without it whipping around and killing you.?
It is also a repitition job so time is off the essence.

j king
03-05-2017, 06:09 AM
http://img.photobucket.com/albums/v24/ikimjing/my%20stuff/Picture003.jpg (http://smg.photobucket.com/user/ikimjing/media/my%20stuff/Picture003.jpg.html)

One way

Chris Evans
03-05-2017, 06:13 AM
Thirteen foot long ! I am outa here. Seriously how much of the bar do you need to machine and is it threaded ?

boslab
03-05-2017, 06:38 AM
Roller stands and a tight sliding fit pipe over the hex, they iongest length of hex I could order was 6m!, that's a hell of a standoff.
We often worked 6.5 m tubes in the lathes in work, mostly between centres with fixed steadys, somewhere home built but we were lucky the long machines usually had pallets of steady rests, one per pallet, a steady for a big craven lathe cost as much as a brand new lathe ( 12" swing sort of thing)
Mark

Mark Rand
03-05-2017, 06:45 AM
A length of 60mm (or whatever is avaialble) plastic drain pipe tied down to convenient supports to keep the bar straight. The idea is that it stops the bar from bending too far and getting to the point where centrifugal force overwhelms the strenght of the bar.

Being hexagonal, it'll rattle like buggery :-(

Peter.
03-05-2017, 06:46 AM
This was asked by someone else and I am curious to know how to do it.
If you need to machine a hexagonal bar of 35mm diameter and the bar is 4meters long,how do you support the outboard piece without it whipping around and killing you.?
It is also a repitition job so time is off the essence.

Several plummer bearing blocks on a steel channel and knock up some hex inserts for the bearings to accept the stock perhaps?

Ohio Mike
03-05-2017, 08:13 AM
Something as simple piece of plastic pipe may work for you. Since its a hex you could cut a bushing with an inside diameter to the outside of the hex as a tight slip fit, and then cut the outside to match the pipe on your stand. Simple plastic bearing. On simple one off round shaft jobs I've had luck just running the piece in the plastic pipe loose you just watch your speed.