Flat bed grinder/polisher on a budget

[unicorn]

For those who want a flat bed grinder/polisher that costs less than an arm and a leg. It's not perfect but it does work. Buy a second hand potters wheel. Get a piece of plate steel about 5 mm or 1/4 inch thick cut into a circle just
smaller (2mm or 1/8th of an inch) than 14 inches dia, so the discs overhang the steel disc and are easier to remove. Bolt this steel disc to the wheel head of the potters wheel with countersunk bolts.
Next step is optional but worth it: Build a simple metal frame to raise the potters wheel up to waist high. These can be purchased off the shelf for some potters wheels.
Hang something heavy from the pedal ( I used a concrete building block). Get a fishpond pump and a large bucket, then secure a thin hose from the pump to the splash pan of the wheel, put the bucket under the overflow. Order some 14 inch diamond discs and a felt polishing pad and some cerium oxide and you're away.
I had, until recently, been using one like this for a few years and found it to be very serviceable. The other thing you can do is to have an electrician disconnect the start winding of the motor. This means you will have to start the motor by hand, but you can start it in either direction. Being able to run the machine in either direction will make the diamond discs last much longer.

[iaff84]

Got any pictures you can post? I have never used a diamond disc setup, just iron, stone and such. Never tried also because of $$$, and did not know if it would be better than what I use now. So this may be another way to try.
Dennis Swan

[unicorn]

Hi Dennis, the diamond discs are getting cheaper all the time. I've only ever used diamonds so I can't compare. The discs are magnetic backed so changing grits takes about 3 seconds. I think I've attached a pic of my old rig, the new one I built has a 20 inch deck, though a lot of people opt fro 24 inch ones. You really start to talk expense when you get to that size. However the discs do last for ages.
Cheers
Jon

[iaff84]

Thanks for picture. What speed do you run this? And why do you feel that running both ways makes them last longer? Do you ever "dress" the pads to clean them?
When they run the "store" bought machines, do they recirculat water with a diamond coolant to help clean wheels?
Sorry for so many questions, this is interesting.
Just one more , what polish compound do you use? I am using Quest 90 from Salem Dist. It works as well as anything I have ever used.
Dennis Swan

[unicorn]

When you reverse the direction it automatically dresses the disc, the diamonds wear in one direction, reverse the rotation and the diamonds present a newly sharp face to the glass. Cleaning is really not necessary. Personally I recycle the water, but my pump is up the top of the tank, so the glass particles fall to the bottom.
As the water is flowing constantly across the disc and the disc is spinning it stays pretty much clean. I'm guessing the disc spins at a few hundred RPM. I finish with 3000 grit cerium on a felt disc. I just use water, there seems no need for coolant additive.
Cheers
Jon

[bert weiss]

Jon

While there isn't need for coolant additive, I believe it will extend the diamond life. It comes as a concentrate, and you don't need much.

[unicorn]

My water tank is about 35 gallons and if I have a big week I would probably add that much more water to it. You loose a fair bit that just flies of the disc and is not caught by the brush barrier as well as loss through evaporation, I live only 12 degrees below the equator. Besides, the discs I use are unbelievably resilient, the 60 grit discs last me about 2-3 years and the finer ones I have not managed to wear out yet.
Cheers

[DrDichro]

Very useful idea. I think I will look into getting a used potters wheel. For last ten years I've been using an upright disc sander system that works great with 7" DIA diamond and a garden sprayer water wand (encapsulation and recovery), but I would like to jump to 20", and go reversable as well.