Circle/semi-circle forming in sheet steel

[negativ3]

Hey all you,

I am looking for a respectfully useful (read not expensive) way of forming circles from mild steel strips.
My raw material is 1200 x 20 x 0.8mm.

I m looking to get 380mm OD circles "bands" or as near as damn it (tolerance not tight).

Thick wooden form and a hammer?
Vise and nibble at it but I think that will give me facets?

My plan was to drill a small securing hole one end of the strip, screw it to the outer face of the wooden form, and have at it with a hammer, adjusting the size of the template if necessary to get the radius required because there will be a tad springback.

Yea, I have a few to do, 30ish.

Any nuggets of wisdom would be appreciated!

Cheers!

 

[Larry Dickman]

a template and an air nibbler should do it

 

[boslab]

Rotary circle cutter is good, you can shear circles up to the sheet width, you drill a pivot hole, drop the sheet on and wind the handle, I’ve got one I found in a scrap pile
The base is like a length of unistrut with a movable pivot .you could cobble one from an air shear or nibbles if you can’t get one, also useful for round flange gaskets
Like,

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Mark

 

[dalmatiangirl61]

Are you butt welding the ends or overlapping and riveting? Decide that then cut to length, wrap around form and connect ends.

If bands, and they need to hold circle shape with ends loose, roll them.

Do you want flat circles, or bands, you used both terms so not sure what desired product is.

 

[dgfoster]

My shop-made pinch roll would do that job in an hour or two. That's what you need. Have a sheet metal (Heating and Air) shop do it on their rolls. Pinch rolls work better than slip rolls.

I made this one a while back. Not a picture of mine, but identical design.
This image is from a fairly good thread on the subject:

Roll design



Pounding them to a form can be done, but, if you are being fussy about the end result, it will take a very long time to get round, fair, and clean results.

Denis

 

[Pattnmaker]

Apart from maybe on the ends no hammering will be necessary or even helpful. You want an arm that swings off the center of your circular wooden form that presses the steelto th form. You will either need a way to clamp one end so you can do part of the circle then feed it through or a way to move where you clamp you form. You will end up with flats on each end with pretty much any way you do this unless you work them out by hand. If the ends need to be perfect often the easiest thing is to start with over length stock and cut the ends off.
I have made big wooden bending forms like this for production bending of aluminum extrusions. It takes some experimenting to get the radius dialed in but works well

 

[Overland]

If I understand correctly you have 3/4" wide, 1/32" thick stock, 4 ft long you're trying to make into a hoop, like a barrel hoop.
Just hold the 2 ends and bring them together. No tools or forms required, unless I'm missing something, of course.
Bob

 

[metalmagpie]

Can't you cut your strap a couple of inches long, overlap the ends, and rivet? That's what coopers have done building barrel hoops since the Middle Ages.

Is it super important to be round and planar and yet not be connected?

Need more info.

 

[DDoug]

Hey all you,

I am looking for a respectfully useful (read not expensive) way of forming circles from mild steel strips.
My raw material is 1200 x 20 x 0.8mm.

I m looking to get 380mm OD circles "bands" or as near as damn it (tolerance not tight).

Thick wooden form and a hammer?
Vise and nibble at it but I think that will give me facets?

My plan was to drill a small securing hole one end of the strip, screw it to the outer face of the wooden form, and have at it with a hammer, adjusting the size of the template if necessary to get the radius required because there will be a tad springback.

Yea, I have a few to do, 30ish.

Any nuggets of wisdom would be appreciated!

Cheers!

Tools avail ?

could it be possible that you just can't doo it ?
Always there is the method of subbing it out.

 

[negativ3]

Guys, totally missed all your responses as I never got any email notifications. Let me review and i'll respond soon. Thank you.

 

[EPAIII]

Yes, this definitely sounds like a sheet metal job to me. There are a number of roll type machines available, some at quite reasonable prices. I have done work like this on the import three-in-one machines and it was easy once the rolls were adjusted for the radius I wanted. Just feed the stock in and crank. With your 20mm width, you don't even need a very big one. Just a quick search:

sheet metal roll machine at DuckDuckGo

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duckduckgo.com

My shop-made pinch roll would do that job in an hour or two. That's what you need. Have a sheet metal (Heating and Air) shop do it on their rolls. Pinch rolls work better than slip rolls.

I made this one a while back. Not a picture of mine, but identical design.
This image is from a fairly good thread on the subject:

Roll design

View attachment 369453

Pounding them to a form can be done, but, if you are being fussy about the end result, it will take a very long time to get round, fair, and clean results.

Denis

 

[negativ3]

Sorry for the confusion, yip it's bands i'll be bending. Looks like a cheapo roller is the way to go to get niceish bands, and will do for light duty stuff in the future. Thanks.

A tack weld would be nice but these will be punched and riveted along their length (circumference), so being in-shape up front is important.

Andy