For Those Using Gray Grinding Wheels - How Course Can You Go?

[Chris Griggs]

So I'm a big believer in using cheap course gray grinding wheels on regular speed 6 inch grinders. With a well dressed wheel, and some care, I have no problems using a 46x gray wheel to grind to a burr on regular tool steel. I'm not trying to convert blue/white wheel users with this thread, rather I have a question for those of you who also use gray wheels. Other than David W, Bob R, and Larry Williams, I'm not sure how many other folks here use gray wheels but hopefully a few of you can give me some insight into my question.

How course of a gray wheel can you get away with using? As anyone who grinds knows, coarser = faster and cooler. I currently use a 46x wheel and am fairly certain that I've heard people say they use 36x wheels. Well today, I was looking at McMaster-Carr's site and saw that they sell a 24x wheel.

So is there a point at which a wheel becomes too course? As in, will the grinding scratches be so deep that a 1k stone won't adequately remove them? Or will the grit be so coarse that it will actually rip chips out of the edge of a blade? Anyone tried a 24x? Should I just stick with using a 36x or 46x? Insights appreciated?

[David Weaver]

I have also used 36 and 46. No clue how coarse 24 would be, but the 24 grit discs I've seen look pretty hairy.

You can be pretty aggressive with 36 and 46 and have no issues if they're dressed. My biggest issue with the gray wheels is not the abrasive surface, but how out of balance they can be sometimes.

I got two brown "premium" wheels from mcmaster carr (they're not that expensive), and like those, too. I like them a lot, they are not quite as hard as the gray, but they're still hard and they will glaze and need to be dressed. I'm indifferent about their hardness vs. the gray ones, but they are better balanced. One of them was dead on balance and the other wasn't too bad. They could probably be gotten more cheaply than the $18 or $19 they were from mcmaster. Haven't burned anything in a long time, and when I do a maintenance grind, I usually just use my palms to cool the tools.

[Archie England]

where's the best places to purchase better 36grit grinding wheels. I've had some serious balance issues on occasion, too.

[Roy Lindberry]

I use a 36 and don't have any problems honing an edge with my oilstones. I keep a jar of water handy to constantly cool the steel, though. It heats up pretty quickly.

[David Weaver]

The only way you'll ever get rid of balance issues guaranteed is to get one of the one-way systems, though odds are a lot better for good balance with expensive wheels, I guess. My white wheel was fairly far out of balance, the gray ones I have that are stock with only one hole size are woofers, too.

Archie - you have one of the baldors, right? I have the 6" with cast guards, and unfortunately, you can't fit the oneway system on and still get the outside guard covers on, but it's so smooth i don't care if the outside covers are on.

[george wilson]

I'll never go back to gray wheels. White wheels cut so much faster and cooler. Haven't used gray for decades. When I was a kid,I'd grind gray wheels literally from a 6" wheel down to a 2 1/2" wheel making knives.

[Chris Griggs]

I have also used 36 and 46. No clue how coarse 24 would be, but the 24 grit discs I've seen look pretty hairy.

You can be pretty aggressive with 36 and 46 and have no issues if they're dressed. My biggest issue with the gray wheels is not the abrasive surface, but how out of balance they can be sometimes.

I got two brown "premium" wheels from mcmaster carr (they're not that expensive), and like those, too. I like them a lot, they are not quite as hard as the gray, but they're still hard and they will glaze and need to be dressed. I'm indifferent about their hardness vs. the gray ones, but they are better balanced. One of them was dead on balance and the other wasn't too bad. They could probably be gotten more cheaply than the $18 or $19 they were from mcmaster. Haven't burned anything in a long time, and when I do a maintenance grind, I usually just use my palms to cool the tools.

Agreed. I've had no issues with the 46 gray wheel. It's plenty fast and I can count on one hand the number of times I've burnt an edge, and even then its been very minimal. Quick touch ups don't really even require quenching. A light touch and a well dressed coarse wheel, I'm convinced, are far more important than wheel type. I have a 60 I want to replace so I thought I'd see what you a and others had to say about the 24. I'll probably just grab a 36 for those times when I really need to grind a lot away. At some point I might try one of those super cool wheel that TFWW sells, but for the price I think gray wheels do a fine job. Perhaps I will try a brown just for better balance. I think I was lucky in that the gray wheels that came on my porter cable grinder ran surprisingly smoothly.

[Archie England]

I'll never go back to gray wheels. White wheels cut so much faster and cooler. Haven't used gray for decades. When I was a kid,I'd grind gray wheels literally from a 6" wheel down to a 2 1/2" wheel making knives.

George, are you referring to white wheels (AlOx) at 36 grit? So, just better wheels?


David, yeah, my Baldor 6" is the best? I bought it from another turner who had already outfitted it with better, balanced wheels plus the Oneway wolverine jig system: it's one sweet set up!

[David Weaver]

Agreed. I've had no issues with the 46 gray wheel. It's plenty fast and I can count on one hand the number of times I've burnt an edge, and even then its been very minimal. Quick touch ups don't really even require quenching. A light touch and a well dressed coarse wheel, I'm convinced, are far more important than wheel type. I have a 60 I want to replace so I thought I'd see what you a and others had to say about the 24. I'll probably just grab a 36 for those times when I really need to grind a lot away. At some point I might try one of those super cool wheel that TFWW sells, but for the price I think gray wheels do a fine job. Perhaps I will try a brown just for better balance. I think I was lucky in that the gray wheels that came on my porter cable grinder ran surprisingly smoothly.

If they're smooth spinning, I'd stick with them (60 grit issue notwithstanding). I keep two identical wheels on my grinder, but one is dressed with a crown and the other is dressed closer to flat to grind unhardened steel to a marked line or to grind irons that have camber.

My old grinder (ryobi) would walk all over the place with the cheap wheels on it, it had to be clamped down. The baldor grinder I have is on a pedelstal stand, and it made a racket with unbalanced wheels that were on it (they were cheap gray norton wheels, I think of the type with a single small hole instead of bushings).

[Chris Griggs]

If they're smooth spinning, I'd stick with them (60 grit issue notwithstanding). I keep two identical wheels on my grinder, but one is dressed with a crown and the other is dressed closer to flat to grind unhardened steel to a marked line or to grind irons that have camber.

My old grinder (ryobi) would walk all over the place with the cheap wheels on it, it had to be clamped down. The baldor grinder I have is on a pedelstal stand, and it made a racket with unbalanced wheels that were on it (they were cheap gray norton wheels, I think of the type with a single small hole instead of bushings).

I keep the 46 grit wheel setup up with the cover and tool rest on the right side of my grinder, as it is the wheel I mainly use. I generally keep it crowned but lately have been expermentiing with a flat surface.

I had been keeping the 60 grit wheel on the left side uncovered w/o any tool rest for those times when I want to do an odd grinding operation and the cover gets in the way. I pulled the 60 grit wheel off this morning since I wasn't really using it at all, and now I just have an empty spindle on the left. Didn't seem to throw off the balance much, if at all. My assumption is that one less wheel is one less thing to potentially throw the grinder out of balance as long as the spindle is running true on it axis.

The vibrations I get I would describe the as small and high frequency. When I've adjusted the wheel before, I have occasionally had the grinder slide around a bit from the vibration, but I've always been able to get the wheels in balance enough so that there has been no need to clamp it down. Also, I find that if my grinder does get a bit off balance simply dressing the wheels can improve the balance.

Anyway, I don't really have a need for two grinding wheels so I may just leave the spindle empty. I still may switch out the 46 for a 36 just to have more speed on those occasions when I'm grinding off a lot of metal.

[Peter Evans]

The "Useful Grinder Data" booklet of the Universal Grindeing Wheel Co Ltd c. 1935 had the following recommendation for chisels:
Wheel surface speed 5,000 surface ft/min, or 2,387/3,183 rpm for an 8"/6" wheel (my vintage 8" grinder is 2850 rpm, so about right)

Grit - 30 to 46
Hardness Grade - M to P (which is defined as Medium)
Bauxite Wheel (not the White Wheel, which gets a recommendation in the booklet only for surface grinding)

To quote the Guide on White Wheels:
"Owing to its exceptionally fast and cool cutting properties it is especially suitable for surface grinding, whether it be hardened steel, soft steel, or cast iron, and gives excellent results when used in a tool room" - sounds like a pretty good recommendation for edge tools to me! Perhaps the cost difference led to the recommendation.

I use a 60 grit White Wheel (which should be a 46 or 30, but most coarse I could find at the time) for gross grinding like squaring an edge at 90*, and a 46 grit Blue Wheel (hardness K) for bevels. The Blue Wheel is a delight to use, but of course wears fairly quickly...

[Peter Evans]

The Australian Abrasives Guide of 1962 suggests for chisels:

White Wheel
60 grit
Hardness K

which happens to be the wheel I have.

[Johnny Kleso]

White 46-H is the perfect wheel for grinding tool steel..

You can use a Gray grit but it may be very hard to find a H (hardness of the bond from grit to grit)

The white wheels have a higher quality grit..
If I used a gray I would not want a wheel wider than a 1/2"

You can buy NOS white wheels at eBay for 1/2 cost of new,all day long but you may have to wait a few weeks for a special type or size..

eBay> Business & Industrial > Manufacturing & Metalworking > Metalworking Tooling > Cutting Tools & Consumables > Abrasives > Grinding Wheels

PS: most industrial wheels have a large center hole, all you need a "grinding wheel bushing" from MSC or McMaster that costs a whole dollar..
Also any wheel with in a letter or two from a H is fine like a G,H,I as not all makers make ever hardness.