how to heat metal to straighten?

   / how to heat metal to straighten? #1  


Silver Member
Sep 27, 2004
upstate South Carolina
Kubota M6800 4WD
Another dumb question but here goes. Several parts on a disc are bent, such as where the top link attaches. These parts are simple steel flat stock, up to 1/4 inch thick. Never having worked metal or welded, what is the best was to straighten these parts. Obviously I need to heat them, but with what--- a propane torch, Mapp gas, etc? I would rather have something fairly inexpensive. And how about if I need to cut through a part, such as a bent and stripped out 3 pt. hitch pin. Of course I could use a grinder and metal cutting disc. But is there an easier way using some kind of torch? Is there an all purpose simple torch that is handy when a part needs to be hammered and straightened? Home Depot sells several types, I am just not sure how much heat is required to soften the steel enough to bend. And does this harm the strength of the part afterwards? No electricity is available on site. Any precautions or relevant tips?
   / how to heat metal to straighten? #2  
Without seeing pictures of the bent parts in question, it's tough to give you a specific answer.

However a straight propane torch won't get hot enough for large/thick parts. The same pretty much goes for MAPP torches, though they get hotter than propane. I'm guessing you'll need oxy/acetylene or oxy/propane to get the heat you need. To bend effectively the steel needs to be red hot. Unless you are dealing with a hardened cutting edge or other part that is hardened; I doubt the heating and cooling will effect overall strength negatively.

Can you get a Sawzall with a metal cutting blade in the areas of the implement needing cutting? If no power, try a cordless Sawzall. I have an 18v one that I like; but I'd get the newer 28v one if you can afford it.
   / how to heat metal to straighten? #3  
You will need an oxy-acetylene torch to heat metal hot enough to bend. You can run these torches on Propane rather than acetylene IF you buy a special tip designed for Propane/Mapp gas for cutting and heating. You can braze with Propane but you cant use steel rods and weld with them. In order to weld with an OA torch, you must use acetylene and the acetylene welding tips.
The draw back to this is the cost of buying the bottles or renting them which charges you by the month. Filling them also is a pain as some places will only fill bottles that they sell (TSC is one of those). However, if you want to heat thick metal, that is about your only choice if you dont have electricity. Some times it is better to just cut out a bent piece of metal and replace it rather than try to straighten it due to the time it takes to heat and beat and twist etc. If it is a simple bend, by all means heat and straighten,but if it is bent and twisted, forget it, just whach it off with your OA torch and fit in a new piece, weld it in with your portable welding machine. You can also weld with some heavy duty car batteries in a pinch. I believe there is a thread here on TBN that discusses that and there is also a battery welding machine that you can buy but for the $400 that it cost, I would just spend a bit more and get an engine powered generator/welding machine.
As for harming the metal, you can definitely do that if you overheat it. ON most low carbon steels that farm equipment is made from, if you dont get it hotter than cherry red you wont hurt it. Always avoid heati it to an orange color because you stand a good chance of damaging the steel if you get it that hot. There are some charts that you can find on the internet that shows the colors acheived when plain carbon steel is heated and the approximate temperatures of the metal when it is that color. For farm repair, these are as good a temperature guide as you need. It isnt necessary to buy a laser temp gauge to accurately determine to within 5 degrees what temp you have reached. You could also acetylene weld your broken pieces back together, but that takes a lot more expertise than it sounds like you have. Acetylene welding is one of the hardest things to learn, much more difficult than electric arc welding.
Hope this helps.
   / how to heat metal to straighten? #4  
Can you remove the parts and use a hydraulic press or anvil.

   / how to heat metal to straighten? #5  
You defenately need oxy/acet oxy/prop dont worry too much about heating to an orange colour (sorry gary) it is not so much the heating but the cooling down that causes the problem allow to air cool and you should not have any probs if you cool down with water you can cause the steel to crystalize making it brittle by hardening (also makes it hard if you need to drill there later) handy if you want to harden a wearing point but there are better things to use than water it is a very good skill to have maybe there are some adult education classes available near you to learn
   / how to heat metal to straighten? #6  
An oxy-acetylene torch is deffinatly what you need. They work great and will do a multitude of jobs. However they can be very dangerous if you use or set them up incorrectly. At the very least get a good welding book and read it, also ask questions and listen very carefully to the guys at the welding supply store where you get your cylinders filled. A much safer approach would be some training at a vocational school or an adult ed class.
   / how to heat metal to straighten? #7  
Oxy-acetylene and rosebud torch. With a rosebud you will be able to heat a much larger area and don't have worry about getting to much heat in one spot.
   / how to heat metal to straighten? #8  
I agree.. for light heating and bending.. propane and mapp are ok.. for more.. get a real set of bottles..

If you have those bottles.. you can cut as well.

otherwise many of us use sawsalls.. or metal cutting discs on die and angle grinders.

can always get a plasma cutter if ya got deeper pockets..

   / how to heat metal to straighten? #9  
I agree with all of the above but sometimes its easier to buy a new piece of steel and drill any holes and replace the part. That is " Sometimes"

Good Luck.
   / how to heat metal to straighten? #10  
Another way to heat it is with a carbon-arc torch. It is a set of 2 carbon rods in a holder set of handles thay attaches to an arc welder. It produces a very brilliant, extremely hot "soft" arc. It is cheap and will easily produce the heat needed.