Bending flat bar the hard way....

I want to bend some 20mm x 3mm mild steel flat bar edgewise into a quadrant of 16" radius. The idea is to then drill it with 6mm holes every inch and use it to make a steady bar between the two fender stays on my rear fenders (see pic below).

So.... I don't have an oxy-acetylene torch (I do have a MAPP gas torch though) or any edge dies for my cheapo Clarke bender. I was planning on putting it in the vice and giving it a small bend every 1/2" or so and then running a flap disk around the edge to smooth it off. Maybe a piece of 12mm plate with a close fitting slot would be easier?

Any ideas of a better way to do it? I know I could have it laser cut from flat plate (in stainless with holes and all ready for polishing yet) - but I'm a bit boracic lint at the moment.....

 

20mm x 3mm? what is that in American measure?

 

Should be easy, what is that, like 1/32 X 1/64'?

 

About 7/8 X 1/8. I can't seem to see what you mean. You want a full arch to carry the fender? Why not bend it cold over a tire or just a steel wheel a little at a time? No flats to grind, smoother bend. Is that the idea?

 

Speaking english might help Oh wait that's why we cant understand you.

 

It's obvious...what he wants to do is to 'edge bend' some flat steel. That means he wants to bend it so the thin edge - the 3mm edge - is arced.

Unfortunately, that is dang hard to do with any sort of good result. I sure don't know how you would do it. I know how to do it with copper, but that is softer and a pretty fancy machine is used.

 

Make a wooden form cut to the radius out of 3/4" plywood mounted flat to another piece of plywood for the base.

Have a bolt or another block of 3/4 ply in the base ply mounted so you can hold the metal captive at one end of the form.

Heat the steel,slip it between the form and bolt, then bend the steel around the form.

repeat for the others and they should all come out the same radius

 

I think you will need to make some pie cuts on the edge and then fill it in with weld once its bent. trying to bend a piece of metal that way without any relief cuts would be nearly impossible

 

OOPs, I just reread your post, you could do it my way with the steel flat and bend edge ways, but you'd have to make an over hanging top piece of ply so that between it and the base is the thickness of the steel to hold it from twisting.

 

Yes - that's it. Bending it the other way is easy.... I do that over an old wheel,a propane bottle or the lamp post outside my house.

I'm quoting millimetres because that's how steel stock (and just about everything else) is sold over here.

Thanks for the suggestions. I will play about with it and see what happens. Might have to save up and get it laser cut in the end.

 

3mm is too light to hold up those fenders without them flopping all over the place and maybe hitting the tire or stress cracking and falling off. Double it.
to bend it to the contour of the fender, make a plaster splash of the contour and use it for a pattern.

 

Lay a pattern out on flat sheet metal and use a cut-off wheel on an angle grinder.

 

Do you have s**** yards over there? Go buy a piece of 1/8" and cut out what you need. Trying to edge bend 1/8" without a jig and O/A would be hard to make it look good.

My.02

 

This is not for the ends of the stays themselves - that will be done in 6mm x 25mm flat bar. This is to link the two existing struts about half way along their length to act as a steady/damper bar. It is not structural, it just helps keep vibration down in the same way linking headlamps does.

I could do it with 6mm square bar and get the same effect and have it easier to fabricate.

Shame that I am useless with photoshop otherwise I could show what I mean...

 

This might help see what I'm trying to do. Here's the front fender, see how the drilled section of brake backing plate looks? I want to make something like that for the rear struts and weld on some tabs and bolt the piece on to link the stays to damp vibration.

Not been necessary on the front because the backing plate is bigger and comes further up the stays and I've been able to bolt it all up at that point. They have 3 points of attachment using M10 bolts (sorry - metric again) so the whole thing is very rigid at the front. The stays are made from 1930's bicycle forks BTW - hugely strong and stiff.

 

Do you know anyone with a forge ? Or someone who makes horse shoes ?

 

Edge set it, open up the jaws on your vice about 50mm lay the flat across the
gap on its edge and hit the top of the flat with a hammer. you will soon get it to bend. You will have to dress it on its flat as well to keep it straight as you go.
Easy

 

Maybe it's time you got one?

 

Cutting the arcs you need out of flat stock might be the best way to a good looking part. These guys are in your neck of the woods, how much would they charge to water jet you a few pieces?

http://www.cncwaterjet.co.uk/

 

Hossfeld has a set if dies to bend stuff the hard way, their catalog shows it pretty well. Once you have that image copy it with metal and bend away.

 

Easy way= just cut them out of flat sheet, by what ever means you have available, torch, cutoff wheel, jig saw; but I would make them out of something a little closer to 3/16" thick instead of the 3mm. Unsprung fenders really take a beating.

 

Not cheap over here - you have to rent the bottles from the gas supplier. They won't fill any others. That cost a couple of hundred dollars per year. Fills are MUCH more expensive than over in the US. Also a lot of insurance companies won't insure a property with acetylene located on it.

I might try oxy-propane though.

 

We have a rolling mill in our shop that would do that in less time than we are talking about it. See if you can locate a steel fab shop that has a machine for rolling shapes, ie; angle, tube, channel, pipe and ask if they will do it for you. Depending on the machine you will need 8" to 12" extra material on each end to engage the rolls.

 

If you don't have access to a torch or other source of intense heat or a steel fabrication shop as noted above, you can work it with a heavy mallet over a saddle or anything else to prop it up off a surface. Take your time and it'll come out fine. Dress the edge that you've beaten with the mallet, then do the happy dance.

 

Yep, almost too easy! And you could increase to 4 or 5 mm thickness.

 

Your early suggestion of gripping it in a vice and bending it a little at a time may be worth a try if you've got some s**** to test on.
You'll need it to be long enough so you have enough leverage and it will take lots and lots of little bends just at the vice.
Let us know how you get on.
Cheers.

 

A sledge hammer and an anvil lay it flat on the
anvil and hit it on only on one side one inch apart
make as many p***es it take and you have the corect radius

 

If I understand correctly you want to bend it on the edge (or thinner) side..
Saw cut ~2/3 of the way thru the flat every 1/2" or so, and it will bend nicely without heat...then weld in the cuts...
I have done this a lot and it works great.
Good luck...

 

Set the die pins up in the bender, clamp the flat bar down so it wont snap up, pull it around a little, move it about an inch, repeat. Peen it back flat then go again till you get the desired curve.

 

I have done this with a press and a couple of blocks spaced out. It is not easy with something that thin as you have to play around with getting it centered so it doesn't slip out when being pressed but it can be done.