forming a flange

[Scottowner]

I have cut a thin mild steel disc to 4.5" diameter. I need a 4" disc with a .25" flange. Any tips on how to achieve this neatly ??

 

[Wendelspanswick]

I have cut a thin mild steel disc to 4.5" diameter. I need a 4" disc with a .25" flange. Any tips on how to achieve this neatly ??

Carefully cut a 4" hole in a piece of 3/4" ply, piece your steel blank centrally over the hole with the piece you cut out from the ply over the top and wind up in a decent vice or use a press if you have one available.
If you use a 4" holesaw that should give you enough clearance for your sheet. You can also use a jigsaw and angle the blade down into the ply. Google jigsaw piercing cut.
If using a vice you will need to spread the pressure with some steel plates on either side of the ply.
Plastic chopping boards make a good substitute for the ply.

 

[Scottowner]

That's a good idea. Thankyou very much. I was thinking along the mole grip/pliers route,but your idea is excellent. The metal is 3mm,would you recommend slotting the flange to prevent buckling ?

 

[optima21]

don't think plywood and 3mm thick steel wont go together too well, for that metal thickness you'd need to start off with a piece of steel bar instead plywood

 

[Dee J]

To get such a small tight flange on such a thick plate you're going to need heat and metal former to work it over or a seriously powerful press and some accurate press tools. Otherwise it might be easier to weld a flange onto the plate.

 

[Burdekin]

Could you just weld the lip onto the disc and then planish the weld? Make the lip larger and then just cut it down after welding.

How thick is the steel? If it's not that thick you might be able to use a swager or maybe a pair of vice grips to turn over the edge.

 

[hotrodder]

Might be me missunderstanding things but based on the other thread http://www.mig-welding.co.uk/forum/threads/internal-brazing.59010/ if the tube is 4" OD then whether flanging a thinner sheet metal disc or welding a lip onto the existing disc the wall thickness (or ID) of the tube and the thickness of the divider needs to be taken into account...

shows the bottom of a fuel tank being 'hammerformed' over mdf and briefly mentions that the former needs to be undersized to account for the metal thickness. For a simple round cap/flanged disc the dia of the former needs to be 2 x metal thickness smaller than the desired OD of the finished part
Work the edge over slowly bit by bit and the metal will shrink. Keep concentrating on the high spots, don't let any 'tucks' in the metal get too big/sharp and the low spots will take care of themselves