Help with Grinding wheel for angle grinder....what kind?

-
gdizzle

gdizzle

Well-Known Member
Joined
May 25, 2015
Messages
954
Reaction score
56
Location
los angeles
I have a 4in wheel grinder that I am getting ready to put to work on a few rust areas on my 66 dart. Mainly the rear quarter panel near the bottom, and also the roof seam.

The rear quarter panel has developed a bunch or pimple/blisters and i believe they have already been bondo'd, painted and now it is breaking out again. I want to be careful that my grinder doesnt just eat through the fender like butter.

The roof seam looks to be just rusted at the seam, old seam sealer is all breaking apart.
What type of grinder disc do I use for this type of body work?? Keep in mind I have never done grinding on a car before, so this is my Maiden Voyage.
I also have an orbital sander if that is safer? Thanks for any help you guys.
My current plan is to prep the car best I can, then take it to a MAACO and just have them spray it with their best 2 stage paint.
 
I'm not a body man by any stretch, but for what you are doing, I would be tempted to use a flap wheel. Just keep in mind how much pressure you are using and try not to generate too much heat in an area.
 
gdizzle said:
I have a 4in wheel grinder that I am getting ready to put to work on a few rust areas on my 66 dart. Mainly the rear quarter panel near the bottom, and also the roof seam.

The rear quarter panel has developed a bunch or pimple/blisters and i believe they have already been bondo'd, painted and now it is breaking out again. I want to be careful that my grinder doesnt just eat through the fender like butter.

The roof seam looks to be just rusted at the seam, old seam sealer is all breaking apart.
What type of grinder disc do I use for this type of body work?? Keep in mind I have never done grinding on a car before, so this is my Maiden Voyage.
I also have an orbital sander if that is safer? Thanks for any help you guys.
My current plan is to prep the car best I can, then take it to a MAACO and just have them spray it with their best 2 stage paint.
Click to expand...

I have to agree on the flap disc, and really have to agree about the heat they generate.
Just take your time and don't stay on one spot very long at a time.

Sometimes I do use a wire wheel, since it rips old bondo and garbage right off without doing more damage to the underlying metal.
Here's an example of what can be done in the back yard with a small compressor and no paint booth.
This is Acrylic Enamel single stage with "wet look" hardener.

trunk.jpg
 
Times 3 on the flapper wheel
 
I agree. I tend to use flap wheels from harbor freight a lot more often than actual grinding wheels. They work very well.
 
Roloc/Scotchbrite discs are made for this. They remove paint, primer, bondo, rust without overheating the metal. The 3M ones are more expensive, but last much longer than the generics. Even the cheap Harbor Freight ones work great and you'd only need a few to strip a whole car.
 
Pascamp said:
Roloc/Scotchbrite discs are made for this. They remove paint, primer, bondo, rust without overheating the metal. The 3M ones are more expensive, but last much longer than the generics. Even the cheap Harbor Freight ones work great and you'd only need a few to strip a whole car.
Click to expand...
Never used those, do they work pretty well ? How quick are they?
 
I would go for aircraft stripper first, I know that it is hard to get in some places but it will take off the paint and bondo with out touching the metal, after all of that is out of the way you can start on the metal work.
 
How about the coarse stripping discs? They remove paint, rust, etc... without removing metal or overheating it.
 
dukeboy_318 said:
Never used those, do they work pretty well ? How quick are they?
Click to expand...
They work absolutely perfectly. That's what 3M designed them for. The open core construction doesn't trap heat and resists clogging. A quarter panel usually takes less than 20min down to bare metal.
 
Great ideas guys. Thanks. So I looked up the Flapper disc, and there seem to be a bunch of different grits. What am I looking for? I see 32 grit, or upto 120 grit
 
View attachment 1715020914 Very much agree with Pascamp, post 10. Flap wheels have a place in my shop, but usually not removing paint from a body panel. A flap wheel is made up small pieces of sandpaper glued to a hub, for it to operate correctly the paper is being slowly chewed up and new sand grit and paper takes its place. If the wheel is plugged with paint, primer or bondo, the wheel will not cut and you have a heat problem. This depends on the paint, there are different kinds of paints used I can easily check this by taking a small piece of sandpaper and sanding the car with it, if “balls” on the paper, it will ball up on the flap wheel. Sometimes I do use a sanding disc for large flat areas gently operating the grinder, taking the time not to press into the work area. I don't like having grit marks into the sheet-metal, that's if you don't mind buying the expensive fill and cover primers. The sanding disc can ball up also, usually I take a wire brush (clean one for this purpose) and or an eraser to clean the disc regularly. I like chemical strippers but not all strippers will work well on all paints, you have to experiment. For the chemical to work well you have to glob the stuff on, it does not work if it feels dried, gloves please. You must have the part flat, it will not work properly on door or fender hanging on the car. My own personal feeling, keep this stuff out of body seams and corners, and do not use this around areas that have foam fillers and adhesives, such as under the hood to support frame. Or you may have an dis-attached hood and you may have paint crinkles at the seams where you use the stripper. I by far use the abrasive wheel and the small abrasive quick loc discs. Here again quality counts for me its 5 to 1, HF discs or one 3M disc your choice you decide. I would like to express safety here please! Face mask, safety glasses, gloves, making sure you have the correct wheel for your equipment rpm. They can fly apart whether if they are cheap or not.

DSCN1486.JPG
 
Last edited:
Maybe you know this already, but it's probably rusting from the inside out. I learned that recently as I documented in this thread. So fixing the outside won't do any good unless you also stop the rust from the inside or completely cut out all the rust. I chose to try to stop it from the inside rather than cut it all out, but that was my choice and not recommended by most people. By the way, I used a flap wheel, then a grinding disk, but the flap wheel would have been plenty. In fact, a wire wheel might have been the best choice as MOA posted in my thread.
 
That is a cool thread and looks like what I suppose will be under my paint. You lost me with the caulking gun and your mixture. Will need to re read a few times.
 
You must log in or register to reply here.
-

Back
Top