[dataway]

So I received my 4.5" shrinking disc, the one recommended that is sold on ebay. It does work, which I find fascinating, a very subtle effect ... irregularity just seem to slowly go away. Which I find disturbing because so far I feel I have no idea how to use it.

My big problem is galling, not sure what the issue is but 80% of the time the small sparks start flying pretty quick. Then I re-sand the panel, scotch-brite the disk and start again. No I haven't tried the suggested Dawn yet, supposed I should. Tried beeswax ... gets to gummy, used a thin film of 336 lubricant ... which helped considerably and strangely enough didn't cut down the heat in the panel one bit.

I'm working above the rear quarter wheel well so there is a pretty pronounced curve to the panel and not a lot of the disc is making contact at a time. I fabricated a small 3" or so disk to use with my Milwaukee die grinder for more control in small areas ... works just like a small version, galls a bit less often, probably because I can control rpm.

So what do you guys suggest as the most likely reason for the galling? Operator error? Too much pressure, too long on the panel (max I've been using is maybe two seconds)? Does the Dawn work well to prevent this?

It is working, but I feel my technique must be in error to have to stop because of galling so often.

[RocktimusPryme]

Ive actually never seen one of those. Curse you internet for introducing me to tools I barely need, but will buy anyway.

I was just watching a video on youtube where a dude was using a magic marker as lubricant. The dude claims to have invented the shrinking disc.

[Greg Reid]

Hmmm.. is that disc flat? I thought that they were convex shaped.
Anyway, I'm interested in getting one myself so I'm subscribing because I want to know the answers to your questions also.

Sent from my moto g stylus (2021) using Tapatalk

[dhutton]

I’ve never had a problem with “galling” and I contact for much longer than a couple of seconds. Maybe if you defined the condition you feel is galling. A few sparks is nothing to worry about imho. Maybe you are overthinking this…

Lots of videos on YouTube.

https://www.youtube.com/results?sear...shrinking+disc

Don

[ZeGermanHam]

[mrennie]

I have experienced the galling, but felt it was from the stainless disc not being true and smacking the panel rather than continuous friction. Also get sparks but not tons.

Always use water with a touch of dish soap to cool the panel down, I feel it helps with the friction for the next round and does not leave a terrible residue to clean.

It really is magic how it does so little each time but still works!

[Shiny]

By galling do you mean metal is transferring from the panel to the disc? I don't remember this happening but it's been a while...

I also don't remember sparks.

Did the disc come with a recommended rpm range?

I think frictional heating is a necessary part of the process so would not expect to need a lubricant.

Any chance the panel is not bare steel? Any coating present that might aggravate the galling?

[BB70]

I've held a bar of soap to the disc while spinning it up for lube, seemed to work for me ok.

[dataway]

Soap ... that's an idea. I'll try that.

The disc I received is flat with radiused edges, and the one I made is flat.

I certainly don't mean grinder level sparks, just a small intermittent steam of them. I can feel it get "rough" when the sparks start, the panel gets rough, and it roughs up the disc, which will make the disc bounce some.

Panel is definitely down to bare steel. Yes the heat is necessary, I was surprised how little a lubricant did to reduce heat (which is good), the disc gets hot quick even polishing it with scotchbrite while it's turning.

I watched some of the videos with the guy using magic marker ... I think that's the guy I bought the disc from .... I might try some dikem blue on it tonight, and soap, and dawn

The galling leaves a pronounced rough surface on the body, like a file but not as deep and "textures" the disc. Makes me wonder why they don't make the discs out of steel, far less likely to gall, but perhaps carries away too much heat.

Come to think of it I do have a tube of anti-gall SS lubricant somewhere.

Rocktimus .... I love this little Milwaukee die grinder ... doesn't have the balls of an air tool, but is great for delicate work, it will shut down for a second if overloaded. Has four speeds and a circuit that tries to maintain a specific rpm at each setting, so not just a resistor circuit ... it will try to torque up under load to maintain rpm. Tremendous for grinding welds, spot work on panels, sharpening things .. all kinds of stuff. Get Ro-loc arbor for it and you can get all kinds of discs.

And if you have a dog that doesn't like his nails clipped ... this thing works tremendous, put on an 80 grit ro-loc, speed down to "1" and gently grind those suckers down, also very quiet so it doesn't scare the dog. Way better than crunching the nails with a clipper, just be careful not to generate too much heat. Liked it so much I bought another just for the dog.

[webfoot]

I have a bit bigger SS shrinking disc than that and no galling, if anything it polishes the spot i'm trying to shrink. Is it turning true? Rough polishing surface?
Using lubricant when the goal is to create heat seems counter-intuitive - it only takes a few seconds to get the panel hot enough to quench.

[roger1]

I bought the Wray Schelin 2 disc kit. I only use the large one. I only tried the small one once but I didn't find it useful. I have it on a large powerful grinder and haven't ever experienced galling. Early on I did use a bar of soap to lubricate but I didn't notice any difference than not using anything so I stopped using it.

[dataway]

I'm using a nice industrial quality Metabo grinder. I see the disc in the above photo is very dark, like it's gathered a coating of something ... my discs are very shiny.

The lubricant seems to do little to nothing to reduce heat in the panel, which I found counter intuitive.

How flat where the panels you guys are working on? So far I've only be working on contoured areas where the contact with the panel is very small ... like half a square inch (very small highs) I have a feeling too much heat is being applied too quickly to too small an area.

[roger1]

It's just gotten that color from a lot of usage. It's been used over marker ink many times too. As you can see, I try to use the flat portion of the disc and not the edge.
My build thread shows many areas on my GTO where I have used it. Both fenders and both quarters. I use it in the same manner as Wray Schelin shows in his videos.

[dataway]

I have been tending to use it too much toward the edge I think.

[roger1]

That's what it sounded like to me. Sometimes you do have to use the edge a bit but stay flat if you can. It's still mostly hitting the high spots and kind of brings them down evenly. You'll get the hang of it. It does change the texture of the metal surface a bit and that needs to be sanded with 80 grit on a D/A before epoxy primer.

[Shiny]

Is it working for you in spite of the galling or has that been a deterrent to using it?

[dataway]

Yes, actually it has worked enough to notice. Again, a very subtle change as you go along but definitely noticeable from session to session. Sometimes I convince myself it isn't doing anything and come back the next day, feel the panel and think, damn, that's pretty nice now.
The area I'm working on now has gone from ... that's going to need filler for sure .... to more of a .... wow, I'm just going to have to skim coat that.

[dataway]

Problem solved ... was down in the shop doing some other work and I decided to spray some layout ink on the panel and try to use my little homemade disc to highlight some high spots. And ... wow, a different tool now, no sparks, no galling, can use as much or as little pressure as I want and you can't MAKE it gall if you want to.
Same deal with the big disc now. Ended up spending an hour messing around with it, the area I was working on is almost perfect now, almost to the point where just epoxy primer would be enough.

Also paid attention to keeping it flatter and off the edge of the disc.

Complete turn-around in ease of use.

If anyone is interested I was using Seymore 620-1558 layout ink ... old can I've had around for 20+ years. I'm guessing the ingredients are very similar to a typical magic marker.

[dataway]

And buy the way, thanks to everyone for their advice.

[webfoot]

Glad you got it figured out!