Using a Shrinking Disc

S

strum456

Oldtimer
Tonight I used a 9 inch Wray Schilen shrinking disc on my 34 Chevy hood that was badly stretched and dented from many years of the car being used as a storage rack. I've been using this disc for years, and I am increasingly amazed by is effectiveness. It did an unbelivable job on my hood (I wish I took before pictures). I thought I would provide some pointers for anyone that is new to shrinking discs.

DO:
1. Get the panel reasonably flat w/ a hammer and dolley first
2. Lubricate the disc w/ water/dish soap mix
3. Continuously move the disc over the high spots
4. Start out by rubbing the panel for no more than 2 seconds, quench, and work up from there if needed.
5. Occationally use fine sand paper and a block to clean/resurface your disc
6. Be especially conservative with thinner panels
7. Try to heat large areas as evenly as possible

DO NOT:
1. Hold the disc in one place or at the same angle too long
2. Heat the metal until it discolors (contrary to what some on youtube say, it is NOT necessary to get the metal this hot to see dramatic results.
3. Over shrink the panel by heating too much or quenching too fast for the particular area. Start off conservatively...these discs really work!
4. Use the wrong type of nut on your grinder to hold on the disc.

Disclamer: I am not an expert on body work or shrinking discs. Without a doubt, there are many people on this site that are far more knowledgable on this topic. Hopefully the experts will add to this thread and we will have a useful resource on one of the most under-recognized tools I know of.
 
Some great help tips, but I have to ask, " How would I know if I'm quenching the metal too fast"?
 
The best control you have is how much you heat it to begin with. Also, the faster you quench it, the more it shrinks. Sometimes when I want to shrink something just a little, I use the disc the least amount possible to get results, then keep the shrinkage down even more by letting it cool naturally, or by using a slightly damp rag.

Most of the time I quench as fast as possible by squirting it with a spray bottle and then rubbing it with a rag.
 
I have been using a shrinking disc for a few years, and have had great success with it. I will say that the way I quench is by using a spray bottle or a soaked rag. I also will cool the metal by using compressed air. I don't know what was meant by "quenching too fast", as the metal should not be heated that much using the disc. The metal only needs to be hot enough to produce steam when water is sprayed on it.

Aaron
 
strum456;5514 said:
Tonight I used a 9 inch Wray Schilen shrinking disc on my 34 Chevy hood that was badly stretched and dented from many years of the car being used as a storage rack. I've been using this disc for years, and I am increasingly amazed by is effectiveness. It did an unbelivable job on my hood (I wish I took before pictures). I thought I would provide some pointers for anyone that is new to shrinking discs.

Are you using this disc on a rotary buffer?

DO:
1. Get the panel reasonably flat w/ a hammer and dolley first
2. Lubricate the disc w/ water/dish soap mix
3. Continuously move the disc over the high spots

What RPM are you spinning at?

4. Start out by rubbing the panel for no more than 2 seconds, quench, and work up from there if needed.
5. Occationally use fine sand paper and a block to clean/resurface your disc

What grit are you using?

6. Be especially conservative with thinner panels
7. Try to heat large areas as evenly as possible

DO NOT:
1. Hold the disc in one place or at the same angle too long
2. Heat the metal until it discolors (contrary to what some on youtube say, it is NOT necessary to get the metal this hot to see dramatic results.
3. Over shrink the panel by heating too much or quenching too fast for the particular area. Start off conservatively...these discs really work!
4. Use the wrong type of nut on your grinder to hold on the disc.

Disclamer: I am not an expert on body work or shrinking discs. Without a doubt, there are many people on this site that are far more knowledgable on this topic. Hopefully the experts will add to this thread and we will have a useful resource on one of the most under-recognized tools I know of.
Click to expand...

Thanks for the information. I wish you had taken before and after pictures so we could see the results as I am considering getting one.
 
I am really bad at stopping what I am doing to take pictures. My hood was really stretched. It was sprung negatively, instead of positively. In a matter of 2-3 hours with the disc, I couldn't feel any waves feeling with a rag over my hand.

To answer your questions,

1. I use it on a Milwaukee grinder, and it spins and heats fast. A buffer would be an excellent idea. I plan to try that now that you mention it!

2. You don't have to clean your disc often. When it is looking smeared with metal, I will take some 120-320 to it. I usually use a 120 disc on a die grinder and go over the shrinking disc while someone is running the grinder for me. Then I take it up another step by rubbing a block with 220 or 320 on it.
 
Are you using this disc on a rotary buffer?

The disc should be used on a disk grinder or buffer. The one I use was made to be used with a 7" or 9" grinder. They are also available for the smaller 4" or 4.5" grinders.

What RPM are you spinning at?

My grinder is rated at about 3500 rpm I believe. I have also used the disc on a buffer at about 2500 rpm.

What grit are you using?

The discs are not different grits. They are simply stainless steel metal discs that are made to fit on grinders. The best type, in my opinion, are the ones with a lip turned on the edge, for safety purpose. Keep in mind that these discs are extremely dangerous when spinning.

Hope this helps.

Aaron
 
So if I understand this right the basic concept is using a spinning metal disc to heat the panel instead of a torch or stud gun? I was thinking there was some type of aggregate or texture incorporated into the shrinking disc but apparently this is not the case.
 
I think these discs are so effective because they heat only the high spots that need shrunk and don't heat anything else. Mine has a smooth surface, but some do have grooves (for lack of a better term). Sunchaser discs have grooves.
 
I tried a disc on a makita buffer, didn't work real well. Too slow not enough power. Bought a big makita grinder, works way better.
 
Ideally you want to tap out any "low spots" to make them "High spots". Once they are now "high spots" they can be shrunk with the disc. Yes... the idea is that the high spot is heated and then cooled to shrink only that area. In reality, the longer you wait to quench it, the more the heat transfers, thus reducing the effectiveness.

You actually have more control of the shrinking disc than using a torch.

I have not tried one of the Sunchaser discs with the ripples, so have no idea if or how well they work. I have had good results with the ones from Wray, so see no need to buy another brand. I will also note that in the last 4 years that I have been at the International Metalmeet in Oblong Il. I have only seen the type Wray sells used there.

Aaron
 
When I purchased my disc I asked Wray about using my buffer, but was told it spins to slow... get a grinder. So I dropped the coin for a 7" Makita grinder.
I think the slower speed of the buffer heats the metal slow enough that the heat is allowed to spread beyond the high spots defeating your efforts somewhat. Makes sense anyway.
 
I'll bet you guys are right about the buffer idea. My 9" Milwaukee is a heavy beast, but it is also effective. Really, I would recommend a lighter duty grinder if you are just going to use it for a shrinking disc.

Also, someone mentioned about discs that don't have a rolled lip on the edge. I've never seen one of these, but that would be REALLY DANGEROUS!
 
I recently purchased one of wrays shrinking discs .....it like any other tool needs to be used in the right place. You can do wonderful things with it, or you can make one hell of a mess with it.
It will not magically erase dents....it will remove small deviations in the metal...but you need to work with it..work the problem area out as good as you can with your hammer and dolly then move on to the shrinking disc.( always check your work as you go with a sanding block or lightly highlight with vixen file) shrink, check,hammer,check..repeat.

The key it to use it wisely ..
If your hood now holds water it is time to stop! ,And realize i shrunk it too much .
 
I tinkered with mine a few times, I think it has a lot more potential than what I can do with it, but it has helped out on a project or two.
 
[QUOTE='68 Coronet R/T;5567]So if I understand this right the basic concept is using a spinning metal disc to heat the panel instead of a torch or stud gun? I was thinking there was some type of aggregate or texture incorporated into the shrinking disc but apparently this is not the case.[/QUOTE]
It is as smooth as a newborn babies butt. It hits the highs and heats them, similar to a stud gun, but easier to manage and does multiple spots in an area at once. Metal doesn't need to turn red to be hot enough to shrink, which is a benefit of the disc over the torch or stud gun imho.
 
When you knock the stretched areas up the disc makes contact on those high areas and puts the heat where it needs to go. I haven't mastered it completely but it sure is handy on large weak areas like hoods and roofs where using a torch and stud gun can be really stressful! If you use it too much you'll take the crown right out of the panel, the metal will tighten to the point that the pressure on any glue spots like on a hood inner structure will increase and cause more distortion-so knowing when to stop is important.
 
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