Disc grinder questions

Phillip Patton

Phillip Patton

Knifemaker / Craftsman / Service Provider
Joined
Jul 25, 2005
Messages
5,362
I'm thinking about getting a grinder disc from Rob Frink, but would like to educate myself a little. He sells steel and aluminum discs. Which is better?
Also, he sells flat discs, and ones that have a 1 degree bevel. Seems like the one with the bevel would tend to make the thing you're grinding slightly concave. Is this a problem?
Any advice would be appreciated,
Phillip
 
The reason for the bevel is so that you may grind on one side without the other side affecting the rest of the blade or scale or whatever you are grinding. It works well. It is a flat bevel with the center as high point. I have both steel and aluminum and can't really tell the difference.
 
If you want to grind the main blade bevels on the disc, get the beveled one. If you just want to make things flat, get the flat.

I don't know whether there's an advantage to steel over aluminum. I have an aluminum disc and have had no problems with it.
 
I have a flat disc and have ground blades to 18 inches. As far as steel vs aluminum, steel has more kinetic energy, once it gets going it keeps going. The alum disc works fine but i prefere a steel disc. I have used both, the main advantage I can see is that steel holds up a bit better. I cut my paper on the grinder the alum discs wear out faster around the edges. Her's some pics of my disc.

Chuck
 
Has anyone had any experience using a replacement disk for the 4x48 inch belt + 9 inch disk sander from Grizzly? Are the ones from Rob Frink or K&G a lot better than the Grizzly disk? Thanks.

Phil
 
Like Chuck said above, the heavier steel will provide more torque in the form of kinetic energy. It's the reason heavier flywheels are often installed on 4X4's along with aftermarket clutches.

I've got both and have no real complaints about the thinner aluminum disk except it rings when grinding some surfaces. I find that annoying.

I'll either replace it with a much thicker aluminum or a steel disk in the future.

Whatever you get, make sure it's a 9", that way you can use a sheet of wet and dry abrasive on it. That will leave you some extra hand sanding strips when you trim the excess. It's also less expensive using 9X11" sheets at .50 ea for good 3M than 2.50-3.50 for 9" PSA abrasive disks.

You use 3M feathering disk adhesive on the disk and let it set up till it's sticky but won't come off on your finger when touched. You then apply the sheet of sandpaper and trim off the overhang. I try to keep most of it at one end so as to have a more useful piece for hand sanding blades or what have you. One coating will last several changes in abrasive sheets. You can buy it at paint stores that supply auto body shops. K&G also sells it.

http://www.knifeandgun.com/catalog/adhesive_186655_products.htm
 
pso said:
Has anyone had any experience using a replacement disk for the 4x48 inch belt + 9 inch disk sander from Grizzly? Are the ones from Rob Frink or K&G a lot better than the Grizzly disk? Thanks.

Phil
Click to expand...

They work fine except as noted in my post above. They're thin and ring a lot when grinding. It tends to get on the nerves.

The aluminum ones I used for years were replacement 9" aluminum disks for the Craftsman 6X48" belt/disk sander. They used to cost about $15.00, until Sears got wise to people using them to make their own disk sander/grinders and stopped advertising them. I imagine they're about the same as the ones from Grizzly.

Just make sure the arbor will fit your motor. Many come with a 5/8" arbor and a thin insert adapter for using it on a 1/2" shaft too.

You don't need huge horsepower motors to drive these things. Anything from 1/3-1 HP is fine. In fact a 1 HP AC motor might be overkill, though, it will work fine.
I'm using two 1 HP DC variable speed motors on mine but they have less torque than the same thing in a single speed AC motor.
 
Thanks for the input, guys. I went ahead and ordered the flat steel disc. I'm getting the motor for it tonight and I'll post pictures of it when it's finished.
A couple more questions. Where's a good place to get sheet abrasive? I'm paying $1.30 per sheet at Ace hardware...
Also, I'd like to be able to flip a switch and reverse the rotation; would most hardware stores sell 3 way switches? Never mind, I'll just call....
 
I buy my sheets from industrial abrasives in PA. The last time I purchased US made sheets they were $56/100. I order 400 sheets and they last me about 1 year. I start with 40 grit and use the finer grits mostly with hand sanding. i will go as fine as 150 on the disc but i find it faster and I have more control finishing by hand. It does not take too long once you get the hang of it. Ask your hardware store if they will give you a sleeve discount. They should give you at least 25% off. I only use the hardware store for emergencies if I run out of what I need.

Chuck
 
I've got the true grit model, it's all aluminum, but very heavy aluminum. I've heard steel is better, but the disk on mine is about 1/2" thick and works well for me.

I get sandpaper from GL Pierce, last time I bought any it was 22$ a hundred sheets. Not the greatest paper in the world but better than a lot I've used and works for me.
 
I don't think the weight is a huge deal if you have a decent sized motor. But the steel will definitely take more abuse as far as cutting off sheets of paper, etc.

John
 
I buy 3M only for 9X11" sheets. Not being a snob, but I found from past experience and almost losing two middle fingers on the cheap crap, that it lasts at least five times longer than other brands. I get it by the sleeve(box) from K&G, link above. Auto body paint stores carry it too and you might check to see who has the better price.
I use 80, 220, 400 and 600. At 600 on a disk I'm seeing my reflection very well, it's takes about two minutes on a buffer if I want a true mirror finish on anything done on the disk at 600. I usually just want to make something flat and make sure that all the old heavier scratches are out before handsanding(don't care for mirror finish).
 
How does the disc do when working the plunge grinds? Or do you try to avoid that area?
 
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