Frame Straightening with Heat

[KGBnut]

I've read a lot of threads about this (and the debate of cold straightening vs. heat straightening), but I am not sure I understand the procedure for straightening with heat. None of the discussions say anything about jacks, or levers, or anything else forcing the frame into shape once it is heated.

Am I to understand that you simply heat the underside of the frame, and then hit it with water to cool it rapidly, causing the metal on one side to contract?

I'm hoping to do my straightening without pulling the body. Can anybody speak to using this technique "body on?"

Thanks,

Ken

[Joe K]

Ouch. Heat is VERY difficult to control. And when you're done you have fully annealled steel which is wont to be bent again.

And how do you prove it out straight with the body in place?

Frame off is not that hard.

Joe K

[Bob C]

You can see in this picture that Brent posted that you need to
heat the frame where the metal is stretched to shrink it back
into position.

Bob

[Tim Armstrong]

If it is a sag at the cowl I repaired mine with no heat. It worked great, and you can do it with simple tools. I f you want info PM me,

[BRENT in 10-uh-C]

So we are clear on a couple of things, the heating process does NOT 'anneal' the metal. I realize this myth has been around awhile but even with the (extremely) low content of Vanadium added to the steel, there is not any negative side-effects from using heat.

Second, the temps of the metal only need to warm enough to make steam emit when water is added. I recently participated in a seminar at a workshop held by the Smokey Mtn. Model-A club in Knoxville, and if I recall correctly, the temperature we were heating the metal to was under 400 degrees as observed with a Fluke IR heat gun. My point is it does not take a lot of heat to shrink metal.

[brito36]

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When it comes to repairing a frame, I would highly suggest that you take it to a professional frame shop. It is not advisable to heat a frame, for any reason. Frames are specifically designed for the vehicle, and must be flexible to a point. Heating disrupts the integrity of the unit. Save yourself a lot of time and headaches, seek help from a professional.

[glenn in camino]

I've straightened 2 of my frames without heat by chaining them down to my lift and jacking up the low places with my floor jack

[KGBnut]

I don't mean to seem ungrateful, but so far no one has answered my question. Brent, I know that you are the one that seems to have the most experience using heat. Is my understanding of how it works correct, that is heating the underside of the frame, and then hitting it with water to cool it rapidly, without the need of leverage or jacks?

Ken

[BRENT in 10-uh-C]

Ken, I'm going to send you a PM with my cell #. Call me sometime tomorrow and I will walk you thru the entire process.

[Terry, NJ]

Not to start an argument, but my experience with "Shrinking" has not been so positive. It sorta worked but not as well as I would have liked. I must be doing something wrong, which I readily concede. Brent very kindly walked me through the process, but it still didn't give me the results I wanted. My Coupe's frame was sagged at the motor mount. There was about a 7/8" gap at the bottom of the hood. I understand about the nature of a beam in deflection being in tension and compression and how the side in tension is where the shrinkage must take place. I jacked it up just behind what I felt was the apex of the bend and let the weight of the front end aid me for what it would be worth. Certainly, it wouldn't be fighting me anyway. I heated the long rails individually at the point of the bend and about 2-3" fore and aft of the bend, to about 800 deg. F with a propane torch, I had cleaned off a small area to see the color of the heat. I chose dark red to blue. Once I had reached this temperature. I took away the heat and applied a cold, soaking wet rag. This produced a slight correction. So I tried it again only this time I heated the lower part of the beam (the web) and again, there was some result but the reduction of the gap was small, but there was some correction. Do it again? I don't know, maybe.
On another note; I have a stretched area about 1 1/2" dia, in one of my hood panels. This seemed like a perfect use of the shrinking technique so I tried it. I wish it had worked for me. I even tried hitting it on an anvil prior to cooling (quenching) it. It seems to work for some people and I'd like to know what I'm doing or not doing wrong. I like the concept. There's no doubt the the metal is stretched and have been a Diemaker, I know about stretching/forming of metal. But never once did we have to shrink it!
Terry

[Bruskie]

I straightened my frame as per brets advice & it worked out well. I have worked with metals doing fabrication work & tool & die & one thing you don't want to do is throw water on it as this will make the metal brittle.

[Kevin in NJ]

The principle of metal that we must all accept and understand. When you heat up metal past its plastic point the metal will shrink.

At one point I read the plastic point starts where you get the metal taking the blue color. At this point the pressure from the surrounding metal cause the now more movable atoms the push into themselves. During cooling the pressure from the heat expanded metal does not go away until way after to get back to the solid point. So the shrink stays.

I believe you would want a hotter heat source then propane. A fast heat in a narrow line gives more control in my limited experience.

Frames and sheet metal are low carbon steel and will not suffer any significant effects from heating.

You do not want to quench. The metal keeps a better shape if you let it cool significantly first. I will use a wet rag to faster equalized the temp of the metal.

It is important to allow the metal to fully equalize in temp. A little heat will distort the metal and you will not get it right. I believe the number one reason why metal shrinking by heat is bad to do is because most guys are impatient. You need to be conservative and patient. You must think and plan how you are going to do the shrinks.

[Mike V. Florida]

Originally Posted by Kevin in NJ

I believe the number one reason why metal shrinking by heat is bad to do is because most guys are impatient. You need to be conservative and patient. You must think and plan how you are going to do the shrinks.

I believe that as well. To go along with that practice, practice and a little more practice.

[Terry, NJ]

Kevin, As a Tool and Diemaker, I learned how to quench small parts (I never worked with anything large) We were using water hardening steel (rare today, but good for the drop hammer work) and we quenched in salt brine. This was done with tongs and the work was placed into the brine, never dropped. By "placing" the work into the water you could control or prevent the distortion, also remove if necessary. Water hardening "Talks" to you. However, if the work was just thrown into the brine and landed on it's side, it would shrink on that side and you'd have the inevitable distortion, So I know the method works. I just need the correct application.
Terry

[mshmodela]

I would get the advice from a body shop that deals with ladder frames. Seems to me a home shop person likely cannot heat the frame in large enough area at one... I built some large U beam bumper for my Dad 78' Chevy truck and the cutting of the metal was easy but we need a few torches to heat along what we needed to bead.

[a-bone newby]

my advice is what i do heat a 1 inch wide bottom frame flange and wedge up the web half way up to 1200 or red and let it cool slowly if this is not enough do it again to the left or right of the last heated spot. the straighten bridge steel this way. this is how I do mine hope this helps

[Pete]

Originally Posted by BRENT in 10-uh-C

So we are clear on a couple of things, the heating process does NOT 'anneal' the metal. I realize this myth has been around awhile but even with the (extremely) low content of Vanadium added to the steel, there is not any negative side-effects from using heat.

Second, the temps of the metal only need to warm enough to make steam emit when water is added. I recently participated in a seminar at a workshop held by the Smokey Mtn. Model-A club in Knoxville, and if I recall correctly, the temperature we were heating the metal to was under 400 degrees as observed with a Fluke IR heat gun. My point is it does not take a lot of heat to shrink metal.

This is pretty much how it is still done in the industry.

Many people first learning to straighten stuff use too much heat and spread out too far. You only need to heat about one inch in diameter at a time.
Like someone else said, patience is your best virtue here.

I once straightened a 100 ft long 10 inch H beam with a full twist. It took 4 days but it saved that company several thousand dollars.

[Chris Haynes]

When you heat then quench you are hardening the metal. Hardening also make the metal brittle.

[JohnLaVoy]

It is against the law in California to use heat when straightening a frame. I guess that shows you how bad it is to do it that way.

[Pete]

Originally Posted by Chris Haynes

When you heat then quench you are hardening the metal. Hardening also make the metal brittle.

You need to brush up on heat treating.
You can't harden metal if you don't color it.