I'm about to cut off the old welded on C-channel front bumper on my truck and put on the correct bumper (which came with the truck). The bumper is a bit dinged up on the upper and lower edges and I want to straighten before I install. I've worked with straightening metal before.....but this stuff is more like metal plate than sheet metal. So my question is should I heat it up cherry red and work it hot..........or brute force it and work it cold. You can see in the pics below what I'm trying to straighten. Any advice from someone who's been there is surely welcome.
Heat it and beat it on a solid thick metal surface ( I used an anvil ) with a decent weight hammer. Don't beat the snot out of it otherwise it will stretch then it will be wavy ( especially if you heat it bright red as it gets too soft, dull cherry red makes it just pliable ).
Paul in Janesville, Wisconsin
1953 m37 parts truck
1961 m37b1 finally going together and turning green
and a bunch of other green trucks that are taking over my driveway
MVPA and MVPG member
The temptation with any body/metal work is to beat the snot of out it (as mentioned in a previous post) with a BFH. Thick or thin... your best option is to go easy at first then increase heat and hammer size as you feel necessary. Twenty or thirty taps with a light hammer or light sledge will give you better results than two slams with a 10 lb. sledge.
Work from the outside edge of the bulge towards the middle. Hammering in the center, as mentioned, stretches and thins the damaged area. In 16 or 18 ga. light sheet metal that usually results in an "oil can" effect. The metal can't decide if it wants to pucker in or pucker out. Your bulges or "puckers" have already streched the metal. Your job is to "move" the metal back to it's original thickness in the damaged area.
After working the bent areas you might also try "heat shrinking" what's left of the bulge. It's a tricky art to master. I'm sure there is tons of info on
heat shrinking to be found on the internet. You Tube probably has a dozen videos on the subject. Shrinking may not apply to thick metal like your bumper.
Again, patience is the key to sucessful metal working.
As a last resort you might be able to find and old time bumper reconditioning shop. They can do wonders but they're few an far between these days.
JB
Thanks for the advice!!! To start I think I'll try a combination of bottle jack and a huge vise we have at work. We also have a nice huge press, but it will be tricky setting the bumper up properly to push straight from the inside of the bumper out. I'm not in any hurry, so time is on my side. I just didn't want to do anything stupid that would take me three times the time to fix later. (Like I usually do)
You might want to do some practicing on some scrap metal so you can find out what the steel will do. Presses are good but they can also stretch the metal and start distorting the whole bumper. Like posted above the heat and beat method can work as long as you take your time and don't go overboard on the beating... practice... patience... practice.
Have fun.
Paul in Janesville, Wisconsin
1953 m37 parts truck
1961 m37b1 finally going together and turning green
and a bunch of other green trucks that are taking over my driveway
MVPA and MVPG member
I have straightened a bumper by laying it across cinder blocks and building a fire underneath it. Let it get hot then work it a little and repeat. You could heat it with a torch but the heat is localized and the mass of the bumper absorbs the heat.
Personally I try to avoid using heat or a hammer. I like to get lengths of box tubing on either side of the problem and squeeze them together with some combinaton of a large vice and clamps. Sometimes you need to use spacer(s) one one side or the other to over straighten the bend a bit. If the kink is stretched too much, slit it with a 1/16 cutoff blade and weld shut after aligning.
Bob
As you have noticed there have been several way's mentioned to gain the final results and there really is no right or wrong way and what works for you and the tools you have is a way to get it done, but the key that has already been said is Patience and practice.They will be your best friend so what ever method you choose and they all work take your time and you will be surprised on what you can do with it. My bumper looked like yours and I used several different methods to get the finish that I was looking for, but I had to walk away from it many times to prevent my self from over working the metal and cut down the bleeding.
hb
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