I have a friend that was in the need to fix some stretched louvers. They were on a dash covering the speaker. I suggested a shrinking disk for use on a air powered 90 degree hand grinder. He was not sure what I was talking about so I took some 16 Gauge 304 stainless steel and quickly made a flat 2.125" diameter disk. It worked well but there was room for improvement. The first thing was to crown the outer edge and the second was to in set the mount. The inset mount was the trickiest. I am using a PFR 419-69027 3/8" Die grinder mandrel with a 1/4" shank. http://www.pferdusa.com/products/206/20602/206020903P.html I might be able to offer them for a small sum if any one is interested.
Hey, Not to piss in anyone's punchbowl, but I'd rethink this one!!!! Stainless steel is notorious for work hardening, and coupled with the r.p.m. at which a die grinder spins, especially the small dia. of your disc, could equal serious harm to user/bystander! This is the same problem with cheap-assed offshore cutoff wheels & grinder discs. They are seldom rated for the r.p.m. at which they spin, and built with vurtialy no quality control. I won't go into any legal advise, as I'm no lawyer, about the legal nightmare you may open up if a tool you produce and sell, causes injury or worse! Jus' something to ponder, late at night ,when you can't sleep........................ ''.........is graffiti on the walls of history "
without a 90 degree lip around the outside they will fail. stress fractures form along the outer edge and they will explode. nobody manufactures them without the lip anymore. yes, I had one without the lip and I got a nice scar on my arm to remind me of it. that was at 3600 rpm on a buffer. not sure what would have happened if it was at the 20 million rpm of a diegrinder.
Warning points taken: I will work on rolling the edge back on its self. My little 90 degree grinder can spin up to 18000 RPM, but when I was using it with my shrinking disk I did not operate it that high. It was slow enough that I could get heat on the work area. Air tools don't have the ass like electric ones have. You should Start the rotation of the disk and Stop the disk on the work for your own safety.
I have been using one I made from a piece of 16 ga. 304 for about 10 years now with no problem. Just made a new one out of 14 ga. I check them every time I use them for cracks. So far so good, but now you have me scared!
I looked at mine beforehand too and didnt notice anything wrong till it came apart. It wasnt that old either. I will admit I was leaning on it kinda hard when it came apart. The one I have now I've leaned on much harder though and no problems at all.
I was able to add a 90 degree lip to the outer edge. That really stiffened it up. What do you think now?
You use it to apply friction that causes heat to a direct area of stretched metal. Unlike a flame it wont heat unwanted areas. Once the stretched metal has been heated it is quickly cooled with water or compressed air. This hot then cold action shrinks the stretched metal. Other shrinking disks are much larger in size (4.5" or 8") for use on a electrical grinder or polisher motor. There large size makes it hard to work small areas. This is why I came up with this shrinking disk to work on a 90 degree die grinder.
convx4, so its a metal disc and you just apply it directly to the metal? so its just a spinning metal disc applied to your work area? i understand the cooling it with a wet rag quickly. this is interesting and never understood how it works. why does the disc need a lip then?
Yup it just creates friction and heats up the metal as it spins. Much easier to control the heat than with a torch. The lip keeps them from cracking on the edge and splitting apart at high speeds.
oh i see, this is very cool, iv gotten by without it but i would realy like to try this when i do my roof filler in the coupe. so no one makes them available to buy? this is very cool, how much is this fee you speak of?
Check the link in my signature. I've had great success with a shrinking disc. I'd be interested in a small disc.
Low Springs, No offense intended, but the guy whose video you posted is a rip-off pirate copycat, and barely knows what he is doing. Wray Schelin makes shrinking discs for sale and is a stand up guy. His email: wesparts@charter.net If you are looking for instruction, my youtube videos are in my signature link, try parts 8-12 of Custom Metal Bodywork. I've never had a use for a small disc that a torch shrink would not fix more quickly and quietly, but to each their own. The larger discs are very useful and can actually shape metal, smooth surfaces and, tune up large areas that need shrinking and relaxing. John
no offense taken. it was just intended for him to see and get an idea on how it sorta works. not to go and buy anything from him. i use the 8" with the ridged edges which might be another rip off from some else too.
I have a John Kelly large shrinking disc...It works very well. I think the smaller will work just as well. But it is dangerous and you must treat these discs with even greater respect than you do for any power tool. I wear my welding jacket and a full face mask. Check out Kelly's videos he's a metal magician.
Hey, That You-Tube video on hot shrinking with a torch borders on criminal! No mention of what caused the stretched area, or steps that should be taken prior to reaching for the torch, too large of a flame & again, no mention of correct hammer & dolly usage so you don't create more stretched metal.........'looks like a guarantee for disaster! I guess I should shut up now, and go sit in the corner ,because I know nothing about making videos...........bad painter! no bisket! " Humpty Dumpty was pushed "
Just curious, but can they be made for a 4 1/2 angle grinder? Would it spin it too fast? Would it not heat the surface properly? Reason I ask is I dont own a torch, nor do I own a larger grinder or buffer that the larger shrinker disc will fit in. I have one of the larger discs, but it just gathers dust since I have nothing to put it into. I dont think I can justify buying the larger grinder just to do some shrinking. I doubt Ill ever buy a torch since I borrow the one from my brothers shop and I priced getting my own torch and itll be about $600 for a decent setup with regulators, hoses, and a cart. I have considered buying a buffer, but is that ideal? I can see the other uses it would be good for, but does it spin too slow to make the shrinker disc effective?
mine is mounted on a buffer and works perfectly and doesnt scare me near as bad as spinning it at high speed.
A reversed sanding disc works in a pinch. On a related note why were the old Ingersoll Rand Cyclone die grinders so much quieter and generally better?
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