Metal Spinning in the Lathe

Hello Chapesses and Chaps,

Does anyone here have any experience of spinning sheet metal parts in the lathe? Against a shaped mandrel, as I understand it. It occurs to me that this would be an efficient way to make some parts I have a need for.

Specifically, I'm looking at making a stainless steel torus that is to act as a manifold and expansion joint.

There are plenty of little firms that I could get to do this. I just wondered if it is something that is worth trying.

Carl.

Carl,

I make fuel tanks for my stationary engines out of the copper sheet recovered from emmersion tanks, this is quite thin but still requires some effort to form, I make my own simple formers for the tank end caps, one held in the chuck with the other held in place as a sandwich with the copper trapped by the tailstock. I make my own forming tool which is a 1/2" dia bar with the end radiused and polished as any marks will transfer to the job. I have to remove the copper and heat it to soften it as it work hardens.

If your going to spin stainless I can only assume its going to need even more effort to form around a pattern so will your lathe be up to it because spinning lathes have very strong headstocks.

Martin P

Hi Carl,

It might be more reliable to make some sort of bead roller to use on a section of thin stainless tube. If the size is right the sort of stainless used for things like toothbrush holders and cruet sets can obviously be formed into deep shapes, like cartridge brass. I imagine it would need some sort of heat treatment first.

Neil

Edited By jason udall on 24/05/2014 17:01:00

I spun this cylinder end cover from 22swg steel over a hardwood former, its about 2" dia with a 3/8" return. I silver soldered a ball bearing to a bit of bar which I held in teh tool post as I found it easier than holding a tool freehand. Took two annealings.

I've spun ali with some success, I wouldn't even attempt stainless, its one of those things that at first glance looks easy but isnt.

Edited By Involute Curve on 24/05/2014 17:17:56

Hi all

Does anyone have experience of spinning GWR safety valve bonnets. I am making a LBSC Pansy with many mods to make it more accurate one of the problems is the single safety valve. Doug Hewson does a drawing of a twin safety valve mounted onto the single 5/8 x 26 bush but space inside the bonnet will be very limited. The standard cast item will be very difficult to achieve sufficient space hence the possible spun alternative.

Peter

Very nice, Jason.

I don't think I expressed what I meant very clearly. I meant you may be able to use an off the shelf item like the flask top below as a starting point. The Range and pound stores are a good source of cheap, thin stainless steel items. And those useless travel coffee cups that keep appearing in our cupboards! As the grain runs around not along the cup below, I think it is spun, but I suspect other items are made using dies.

Neil

Standard spinning tool end is shaped just like the end of the forefinger. It must be either fully hardened or case hardened and highly polished. A toolrest is fitted into the toolpost consisting of a steel bar drillled with about three holes spaced out near one end and a peg to fit in the holes, against which the tool is levered. The tool needs a longish handle. Lubrication is needed and use of most common oils will result in failure. The secret lubricant used by Spinners in factories is Tallow and I can vouch for its efficacy. A rotating centre with a wooden pressure pad fitted is necessary. The disc of metal is pressed lightly against the former with the tailstock and the disc edge tapped lightly to centralise the disc. Full pressure is then applied. The metal must be fully annealed as suggested and the tool is worked from the centre outwards. It requires a little practice although it.is very quick. However you have chosen the worst possible metal to try out the process, so I would practise on annealed aluminium first.

Thanks for the replies. Too many issues involved, far easier to have the part made by a small firm.

Carl.