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Bending thin-walled 4130

EvansER89

Aluminum
Joined
Dec 23, 2014
I have a personal project requiring a few bends in some 4130 tubing using my manual bender; 2" and 1-5/8" ODs, both are 0.049" wall, 15<60 degree bends, and both dies have a 7" CL radius.
I have tried several methods and am wondering if there are any others left to test.

Lots of bending lube and elbow grease
Capping both ends after packing the tube with sand
Capping both ends after packing with wet sand
Bending with a bullet shaped mandrel
Bending with a plug/form shaped mandrel

I had mixed results with both styles of mandrel, mostly with kinks forming inside the bend. I'm sure with more testing I could get more consistent results, but the pile of tube scrap after testing isn't cheap...

I'm wondering if one of the ball style mandrels will offer significantly more support than the plug style? Has anybody tried making their own? My googling hasn't turned up many results in how those mandrels are designed so I'm weary of just winging it and ending up with an even more expensive piece of recycling.

As a last minute alternative, is there anybody out there who already has the equipment and would be willing to bend me a few tubes? Some parts of the design are flexible and may be adjusted to suit available tooling/equipment.

I am a rookie with bending this kind of stuff, so please drop some knowledge on me!
 
I used to work with stainless tube of similar size and was as you describe. We'd bend tight radii with a die set on a punch press. For smaller stuff )1/2" to 3/4" or so, we'd use an aluminum mandrel pressed in and after working the part, melt them out. For sizes like yours, we would use UHMW pressed in for a mandrel. Then burn them out. Easy Peasy!!
 
I believe you can buy low temperature melting metal specifically for this sort of thing. I remember a buddy telling me about using it for just what you are planning.


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We had thought about trying water, or ice rather, but I just don't have a freezer on hand big enough for the tubes. Welding plugs in with water could be tricky but might be worth a shot...

I really like the idea of the low temp alloy filler, from what I can tell its reusable so I'll have to look into sourcing that. In the mean time I can probably scrounge up a stick of UHMW and burn it out. My neighbors probably already think I'm up to no good in my shop, I'm sure a nice whiff of molten plastic will do wonders for my reputation.

Thanks for the suggestions everyone!
 
Just have someone that has a mandrel bender do it, I use Tube Techniques in Columbus Ohio. Those guys can do it in their sleep. Just phone them up, 4130 is in stock, by and by it is on your doorstep and perfect.
 
Cerrobend is good for tube, not so good for wallet. Go to tirestore and buy a bucket of old lead tire weights (after checking with scrapyard to determine going price).

You can melt the lead out in an open wood fire, if you have not got a lead-pot big enough to immerse your whole bend.
 
I got a quote or two a few months back but they seemed outrageous so I bought my own bender, which I had been meaning to get anyways. If Cerrobend doesn't work for this stage of the project in particular I may just have to bite the bullet and get it done by a pro.
Any personal recommendations for something closer to home, west coast/WA state?
 
Forget all the suggestions on using cerrobend, filling with sand or ice bullshit.

From 1986 thru 2005 I built 1,100 dirt mods, over 400 were .058 & .049 4130.
Used Greenlee dies in a Dave Williams ( Low Buck Tools) bender.
Never had a kink in a bend.
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I'm betting you re trying to bend it cold? Make a form out of plywood in the shape you want. Fill with sand, heat red hot and THEN bend it. 4130 likes to crack if bent cold.
 
I tried getting it hot, it just seemed to exaggerate the failure, it kinked right away and flattened easier, and eventually split.
The bend itself doesn't require much effort with the setup I have, its just the issue with kinks forming.

What size tubing are those frames? I'm wondering why you had success with your setup and I am struggling so much. My bender is pretty rigid and the dies look like they were machined well enough.
Ideally down the road I will be using even thinner tubing so if I can find a reliable way to do it myself that puts me way ahead of the game.
 
I tried getting it hot, it just seemed to exaggerate the failure, it kinked right away and flattened easier, and eventually split.
The bend itself doesn't require much effort with the setup I have, its just the issue with kinks forming.

What size tubing are those frames? I'm wondering why you had success with your setup and I am struggling so much. My bender is pretty rigid and the dies look like they were machined well enough.
Ideally down the road I will be using even thinner tubing so if I can find a reliable way to do it myself that puts me way ahead of the game.

It does not matter how nice your dies are, If you don't have a proper ID mandrel that withdraws as you bend it you are just pissing in to the wind. The reliable way to do it yourself is to spend big bucks to get the right machine.
 
My question was directed @J.Ramseys post. I'd love to have a legit mandrel bender but that isn't feasible right now, and long term I will be moving away from this process so its not really the best investment.
The bender he mentioned is definitely not big bucks, but it looks like he has had good results, I'd be curious to narrow down the differences.
 
..............but it looks like he has had good results, I'd be curious to narrow down the differences.


The real issue with your bends is the .049" wall of the tubing. Good results can be had without a mandrel with heavier wall tube using non-mandrel benders, but when you get down to thin wall a mandrel set up is the best solution.

I was R&D Mgr. at an aftermarket exhaust manufacturer that bent .049" wall tube (both steel and stainless) in ODs from 1.375" to 2.5". Without a mandrel bender smooth bends ain't happening.


Rex
 








 
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