Surface grinder Wheels

[Sandia]

I need some advice on ordering some grinding wheels for my Harig SG. I have never used it before, just got it set up with some help from RayC. MSC has a sale going on til midnight tonight. The grinder is a 6X12. Can anyone give me some specifics on what to buy to learn on.
Thanks

 

[Ray C]

Start with a 1/2" wide wheel, coarse grit around 46 to 60 but nothing higher (80 and 100 are hard to work with). Medium hardness (anywhere from H, I, J, K). A 1" wide wheel is OK too. Make sure to order the right diameter hole (probably 1.25").

You will find for most work, you will always go back to the 46 grit. Seems counterintuitive but, it gives a great finish w/o showing all your goof-ups.

Ray

I need some advice on ordering some grinding wheels for my Harig SG. I have never used it before, just got it set up with some help from RayC. MSC has a sale going on til midnight tonight. The grinder is a 6X12. Can anyone give me some specifics on what to buy to learn on.
Thanks

 

[Sandia]

Start with a 1/2" wide wheel, coarse grit around 46 to 60 but nothing higher (80 and 100 are hard to work with). Medium hardness (anywhere from H, I, J, K). A 1" wide wheel is OK too. Make sure to order the right diameter hole (probably 1.25").

You will find for most work, you will always go back to the 46 grit. Seems counterintuitive but, it gives a great finish w/o showing all your goof-ups.

Ray

Thanks Ray, appreciate it.

 

[churchjw]

I second Ray's advice. When I got my surface grinder I bought wheels that were way to fine. My thinking was finer grit better finish. Just like a sanding belt right :nono::nono: The fine wheels loaded and dulled to quickly. You probably know this but two mistakes I made early on were not dressing the wheel often enough. Dress it after every job and sometimes during a job. Watching a pro do a die set I was shocked at how often he dressed. The other thing when you are dressing a wheel never go over the dresser if you are not taking material off the wheel. I would often do my last pass on the dresser then bring the wheel back across one last time without moving the depth. A friend told me that last pass was just dulling the abrasive on the wheel.

Jeff

 

[Ray C]

The real issue is heat. Fine grit = heat because the contact area is increased many-fold. A more porus wheel has less contact area. With a surface grinder, you're typically only removing 0.0001 to 0.0002" at a time and when the wheel contacts the piece, there is a localized heat build-up that can easily expand that immediate area by about that much. -Bingo, suddenly the wheel starts grabbing, it digs in and the piece is shot. 46 and 60 grit are coarse enough to remove material efficiently and not generate too much heat. As someone mentioned, fine grit loads-up very quickly and that adds to the heat problem.

There are other issues too like hardness. Soft metal needs a hard wheel and vise-versa.

Surface grinding was surprisingly difficult to figure-out and I still learn something every time I experiment... It is not as easy as you might think but it stands to reason that the harder you try to make something "perfect" the number of things that get in the way increase dramatically.


Ray

 

[churchjw]

The real issue is heat. Fine grit = heat because the contact area is increased many-fold. A more porus wheel has less contact area. With a surface grinder, you're typically only removing 0.0001 to 0.0002" at a time and when the wheel contacts the piece, there is a localized heat build-up that can easily expand that immediate area by about that much. -Bingo, suddenly the wheel starts grabbing, it digs in and the piece is shot. 46 and 60 grit are coarse enough to remove material efficiently and not generate too much heat. As someone mentioned, fine grit loads-up very quickly and that adds to the heat problem.

There are other issues too like hardness. Soft metal needs a hard wheel and vise-versa.

Surface grinding was surprisingly difficult to figure-out and I still learn something every time I experiment... It is not as easy as you might think but it stands to reason that the harder you try to make something "perfect" the number of things that get in the way increase dramatically.


Ray

Yea I was getting little burn marks from the fine grit wheels.

Jeff

 

[Sandia]

I appreciate the advice fellows, so I ordered a couple of wheels yesterday before the sale was over at MSC. I will say one thing, they are not cheap especially the Norton wheels. My grinder came with 3 used wheels, one was chipped badly on the side, afraid to use that one and another was 150 grit, and the third was a 46 grit medium wheel which had been formed to grind a 45 degree on one side. I used that one to chamfer the edge on the radius turner I just made. I was experimenting with it and it turned out OK.

 

[Ray C]

Cheap they are not... That's one of the reasons I suggested a 1/2" wide wheel; they're a lot cheaper. Mainly though, 1/2" wide wheels tend to need less balance adjustment. 1" wide wheels always seem to need the most balance correction. You only need the wider wheels when you have a piece with a lot of surface area.

When you get them, hold it up by the center hole with one finger and tap it lightly with a blunt metal object. If the wheel goes thud instead of having a ring sound, be extra careful with it. I know you have a VFD on your SG so, install the wheel and start it up to about 2000 RPM, let it spin several moments then increase another 400-500 RPM etc... Make sure you wear face protection and have the guard installed. Keep your body parts out of the radial line of rotation. Don't try to dress the wheel until it's spun for at least a minute or so. If at anytime it starts to vibrate and sound like it's going to take wings and fly, kill the motor -quick. A wheel like that needs an external balancer. I've had them so bad, even that would not work. I had a wheel fly apart when I increased from 3000 to 3600 RPM...

Always test the wheel and spin for 1 minute each time you use the machine.

Ray

I appreciate the advice fellows, so I ordered a couple of wheels yesterday before the sale was over at MSC. I will say one thing, they are not cheap especially the Norton wheels. My grinder came with 3 used wheels, one was chipped badly on the side, afraid to use that one and another was 150 grit, and the third was a 46 grit medium wheel which had been formed to grind a 45 degree on one side. I used that one to chamfer the edge on the radius turner I just made. I was experimenting with it and it turned out OK.

 

[4GSR]

Sandia,

I wish I saw your post sooner. I could have sent over a couple of wheels I have on hand that are extras, to try out.)

Ken

 

[Sandia]

Cheap they are not... That's one of the reasons I suggested a 1/2" wide wheel; they're a lot cheaper. Mainly though, 1/2" wide wheels tend to need less balance adjustment. 1" wide wheels always seem to need the most balance correction. You only need the wider wheels when you have a piece with a lot of surface area.

When you get them, hold it up by the center hole with one finger and tap it lightly with a blunt metal object. If the wheel goes thud instead of having a ring sound, be extra careful with it. I know you have a VFD on your SG so, install the wheel and start it up to about 2000 RPM, let it spin several moments then increase another 400-500 RPM etc... Make sure you wear face protection and have the guard installed. Keep your body parts out of the radial line of rotation. Don't try to dress the wheel until it's spun for at least a minute or so. If at anytime it starts to vibrate and sound like it's going to take wings and fly, kill the motor -quick. A wheel like that needs an external balancer. I've had them so bad, even that would not work. I had a wheel fly apart when I increased from 3000 to 3600 RPM...

Always test the wheel and spin for 1 minute each time you use the machine.

Ray

Again, thanks for the advice. I did order 1/2" wheels. I may have to get you to help me set up the VFD to be able to adjust the speed. The way it is set up now, is either on or off..

- - - Updated - - -

Sandia,

I wish I saw your post sooner. I could have sent over a couple of wheels I have on hand that are extras, to try out.)

Ken

Thanks for the thought Ken, I would probably have taken you up on that. Your not very far up the road either, 100 miles matter of fact. Who do you work for in Victoria, Ken.