Need help with high spots

mitch_04

Learnin'
Hi all,
I had messaged MP&C about some problems I was having with high spots. He asked me to start a thread since he though others might be struggling as well, so here we go.

My problem is that I am not sure how to deal with high spots. I have them from butt welds, missing my mark or over doing it when trying to hammer dents/ low spots, and some that are just there. I have a couple body hammers, including a shrinking hammer, a couple dollies, a slapper... that's about it. I'm not sure what is too high, what will hide with paint, etc etc.

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I usually use pick hammer to flatten high spots. If you take your time and don't hurry you can get it fairly close.
 
Mitch, I'm going to add some of your PM....

I have a shrinking hammer (serrated face) but I'm not sure if it's the correct tool. I've tried it in a few spots, both with and without a dolly on the backside, but it just seems like I'm creating a knurled surface.

Two primary shrinking hammers, the rotating type carried by Eastwood, and the knurled you mentioned (what I refer to as the waffle face).

Rotating hammer: I have used this one before, and have found that in order to get the face to grip and twist (shrink) the metal you need to use quite a bit of swinging force. The downside is that there is a fine line between shrinking just the right amount and now you stretched it from hitting too hard. My experience has been that any hammer can shrink, and light taps using regular body hammers may give more controlled results than something that requires a harder hit to provide the rotational force. Counterproductive, to a certain extent. I consider this a gimmick hammer that is difficult to control the results. Perhaps it was the operator in my instance, and someone else may have better luck. If so, good job!

Waffle face hammer: This one has been around for quite a long time and produced by some quality hammer makers, so it must work! It also has been labeled as a gimmick hammer, but that may be due to misuse.. To explain, lets start with Carpentry as an example. Estwing makes framing/claw hammers in both a smooth face and the waffle face pattern. For some that may not be as skilled in connecting the hammer face to the head of the nail, you may see a glancing blow that tends to bend over the nail. Replacing the smooth face hammer with the waffle face one shows less issue with nails deflecting as the waffle face can really be considered as multiple hammer faces. One part of the hammer misses and another picks up the slack. So as it relates to body work, the waffle face is strictly intended to provide a multitude of "hammer faces" to hit and not slip. I think where the misuse of this hammer comes into play is that most of us have swung this hammer like it was the Estwing framing hammer, which is not the intent. This hammer should ONLY be used with light taps, and if you are leaving a knurled surface, you are hitting too hard. Again, it is designed to hit and not slip using light taps. In most cases I don't recommend either of these two hammers to novices as they are so persnickety to get them to work correctly. I find the waffle face to be less of a gimmick hammer, so if you must choose one, use the waffle pattern hammer. If you feel you can't do without the Eastwood rotating hammer, look on craigslist for a used one.. Nobody uses them long after buying them, so you may as well learn your lesson at half price..
 
My problem is that I am not sure how to deal with high spots. I have them from butt welds, missing my mark or over doing it when trying to hammer dents/ low spots, and some that are just there. I have a couple body hammers, including a shrinking hammer, a couple dollies, a slapper... that's about it. I'm not sure what is too high, what will hide with paint, etc etc.

For high spots to either side of the weld, this is normally due to the panel shrinking along the weld line and heat affected zone, the area outside the HAZ is resisting any movement, and the area between the two (about an inch or so outside the weld seam) shows buckling like a sinusoidal wave as it reacts to the shrinking. So if you have high spots / low spots to either side of a weld, this is likely due to shrinking of the weld area is still not stretched enough.. Profile templates taken from the original prior to repairing the rust may be a useful tool to insure you don't stretch too much..
 
Ideally you want to find any high or low spots prior to adding filler. Using a vixen file works well to highlight the high spots (shiny), then do some metal bumping to address the defects. Get things as close as possible and then start with epoxy and filler/high build. For some of the isolated high spots you show above, remember on-dolly stretches, off dolly shrinks. So with the high spots we want to use something that is not going to add any more stretch. You may want to use a donut dolly or perhaps a small shot bag used as your dolly and lightly tap the high spots into your dolly of choice. If the high spots (low spots, depends on point of reference) seem too much for this method to correct, then we may want to revert to heat shrinking.
 
I have done a small amount of research and it seems like a shrinking disc would be a good tool to purchase in the future. I plan to attend Wrays class in the future as well.

As for this car, I'm learning a lot during it. I didn't have a tig when I did the panel replacement, so it seems much of my shrinking is there to stay. Where I can reach I have gotten it much better but a lot of the spots are inaccesible and others I can't seem to get to change no matter what. That is one of the spots that may have gotten imprinted with the shrinking hammer. I didn't start by wailing on it, but I worked up to it.

Since this car I have put a 1/4 on a Trans Am and it went much better. The tig welds move much easier and I found out if you grind the backside everything moves even easier yet (this was also written in a post since I did the 1/4, too bad I hadn't seen it sooner!)

I'm still trying to grasp a lot of the hammer and dolly work, sometimes it's hard to understand (like how the dolly can act as the hammer even though the hammer is what's swinging, if I worded that correctly). I have readthe metal bumping book and that started the juices flowing, but I think a class would help with a few aha moments.

Lastly, how do you know which metal spots with hide with a coat of sealer(epoxy) vs which ones will map? I've put another coat of epoxy over some of these and some spots are hidden, some are visible.
 
Mitch, here are some good sources of info. Nothing against Wray but I'd look into these before I put down big money to go to one of his classes.

https://www.tinmantech.com/
Kent White has years of real world experience and has a bunch of DVD's on all aspects of Metalwork. Plus he allows you to rent the DVD's!

https://metalshapingzone.com/
If you are going to buy just one DVD this would be it, David Gardiner has years of real world experience as well. He jam packs a ton of content on this DVD and it's less than $50 shipped. Get this one, you will not regret it.

http://www.handbuilt.net.au
Peter Tommasini is a great teacher, Another guy with many years of experience His DVD set is a little pricey but it is worth it. He actually makes a quarter panel for a 60's muscle car with nothing more than hand tools and a English Wheel! He also offers Classes when he comes to the US. He has 10 DVD's available.

Watch any of these videos and you'll be able to grasp the hammer/dolly "concept". :)
Like I said nothing against the guy but I'd take Peter's class or Kent White's before I'd take Wray Schelin's.
 
A high spot like you pictured above, I would lightly tap it down, backed up with a sand bag.

I have tried to use the shrinking disk quite a bit. Unfortunately I can't recommend it. It will take hundreds of hours to master it to the skill level of Schelin. The way the disk is made, it is concave. Only the outer 1/4" of the disk will contact the metal. The stainless steel severely galls, which then tears up the sheet metal. It looks like it was hit with a 36 grit grinder when done. After many attempts of using it, watching videos, using soap as a lubricant, I finally gave up. I can get the same results with traditional heat shrinking. I'm not saying the disk doesn't work, but it is not a magical cure for high spots.

Which led me to another experiment. My dad has the O/A torch right now, and I needed to do some shrinking. A quick warm up 1/4" diameter with the TIG torch at 20 amps, followed by a hit with a body hammer, then cooled with air. Makes a quick, controllable shrink.
 
I don't know if this has been addressed, but looking at the panel while wetted with solvent based wax and grease remover can help tell you how objectionable the high area is.

I find that a stud gun with a shrinking tip can help make short work of high spots and help prevent oil canning. The downside is that you burn the backside if it's already coated.

I have a shrinking slapper that I use sometimes, but not as often now that I know how to control the shrinking action of the stud gun.
 
Steel slapper backed up with a shot bag dolly will work with light to moderate high spots. Leaves no marks either. As already been discussed hot shrinking with either a torch or if you have a stud gun for the more severe high spots or stretched areas Shrinking with the stud gun would be more controllable if you are new to this than with the torch.
The shrinking hammers are gimmicks and completely worthless. Spend your money elsewhere.
 
I'd shrink disk those high spots if it was me. I use the Sunchaser waffle discs but I think he no longer sells them. I've had the same one for almost 10 years. It takes a while to get the handle of them like MX442 said. Not as easy as the vidoes make it seem but I wouldn't be without one now.

I have a martin shrinking hammer and dolly and they are a joke. You'd have to hit the metal with the strength of a gorilla for it to do much of anything.

Torch or stud gun shrink will work and you don't have to purchase more stuff. I use a bucket of water and rag instead of air to cool the metal though. Just the way I was tought by a real old time bodyman. He used to take a torch and hit the center and spiral outward the size of a quarter with the center spot the size of a dime red hot. Then he'd grab a rag out of the water bucket and quench. Works great but I like the control of the shink disc.

I have a few of the Kent White videos and he does a good job. I like everything that I have purchased from them also. I almost have his powerhammer done and most of his english wheel built. Not enough time in a day.
 
I have a stud gun, I'll have to give that a shot sometime. I also have access to a torch. Thanks for the video recommendations, it's hard spending that kind of money and not know what ones are worth it.

One question, if you hit a panel with a hammer, created a dent (streched metal?) could you torch/stud shrink the backside and get the dent out? Or could you do it from the front the same? A shrinking disc wouldn't touch the stretched metal from the front, but it could get the back...

I'm still waiting for the aha moment with all this!
 
One question, if you hit a panel with a hammer, created a dent (streched metal?) could you torch/stud shrink the backside and get the dent out? Or could you do it from the front the same? A shrinking disc wouldn't touch the stretched metal from the front, but it could get the back...

I'm still waiting for the aha moment with all this!
Yes, I have done it from the back where there is access. Then I found this (rule #4 & 5). A quote from the Army Institute for Professional Development - Metal Body Repair:
Certain rules should be observed at all times during shrinking
operations. They are:
1 Never quench a red hotspot. Wait until the metal has turned black.
2 Never heat an area greater than that where pressure can be applied at one time with the hammer and dolly.
3 Never use anything but an acetylene torch for heating a stretched section.
4 Never attempt to shrink a panel until it has been roughed out.
5 Never apply heat to a low spot for shrinking. Hammer it out, then apply the heat.
6 If the stretched part of the surface is small, heat a smaller spot.
7 It is possible to shrink metal without quenching each spot with water. However, the shrinking operation is much faster if each spot is quenched with water. Less heat spots are required if the heat expansion is drawn out by quenching, rather than by additional spots.


#3, I disagree. I can do a lot of shrink damage with O/A torch.

I discovered that a sunken stretch will sink further with the wrong hammer and dolly. Following this advice, I learned to raise a sunken stretch to get it to take shape. Then shrink down the spongy spots. Hard to describe by typing. It just takes some practice.

I started using air, because I always manage to get hoses or cords caught on a bucket of water and dump it over.

Don't worry about the aha moment. It takes "X" amount of years to get "x" amount of experience. I'm just a backyard hack working on my second metal repair project, and I feel confident on metal shaping. You have to closely observe the results. If metal is moving or behaving the wrong way, make a 180 degree change and observe the results. Correcting mistakes will teach you a lot.
 
It looks like you have low areas around the highs, why not try some off dolly hammering?
The first two picks are the edge of a hood, which has a seam & brace behind it so I can't really do anything from the back.
The next 2 high spots were probably self created by trying to get out a low spot. Would off dolly still help in that case?
 
The reason for shrinking is because the metal is stretched, that could be by an accident, mis lick with a hammer, or over stretching a welded seam. John Kelly use to have some very good videos on using the shrinking disc, and it showed how much hammer and dolly work he put into the metal before and during the disc use. You can easily change the contour of the panel by unnecessary shrinking, then you need more bondo to fill it in. Just because you hit a panel with a hammer doesn't mean it stretched, but if a dolly was behind it, then it very well may be. Sometimes you can use a pry bar to get behind a brace.
 
So on the 3rd and 4th pics, you think that if I held a dolly underneath the low spots and hammered on top of the high spots, I would have had straightened the metal, correct?

The off dolly is just so against my "common sense", seems absurd that the dolly will move the low spot when the hammer is 2 inches away... I've read about it in the metal bumping books, and I just haven't had it work (yet) so it's hard to think of to use.
 
Its hard to tell by the pictures, but that is the way it looks to me. Put firm dolly pressure on the low areas that are close by, and use a body hammer to just tap the high spots down. The hammer is just relieving the resistance, the dolly is pushing the metal out. You are raising one area and lowering another area at the same time.

Keep in mind, every time you hit the dolly with a hammer, you are stretching the metal to some degree.

Around a weld seam, sometimes you may have to shrink an area that got stretched too much, and stretch another area more, even though it is close by. With the metal covered up like that, its hard to tell what is going on, but some off dolly work is worth a try before you start shrinking, and torch shrinking by someone who is asking for information is not a good idea IMO. A few hits with a stud gun and its done, if it really needs shrinking.

A little time reading the panel will usually help tremendously, get a practice panel and try some off dolly work.
 
From what I've read, I will probably not try to use a torch too quickly. It seems like it's the easiest to mess up, because you can shrink surrounding metal if you aren't careful. I had always planned on fixing a hailed pickup I had, but I ended up selling it. Too bad, would have been good practice (I'm assuming hail dents are just a ton of tiny stretches).

I'll probably re-read the metal bumping book now that I'm in the midst of it, and take the advice given here to see where I end up. Most of these panels are now pretty close to good, I actually haven't had to use much filler at all on them. Many times I had it close enough that I ended up sanding away the filler to where you could see through it, I believe another coat of primer would have probably worked the same.

Thanks for all the help everyone, whenever I get to my other project I'll report back my struggles or successes.
 
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