masonry diamond angle grinder wheel for carbide grinding?

[liveaboard]

I saw a youtube video where someone uses a diamond wheel and a jig in a tablesaw to sharpen a carbide tipped saw blade.
I have some 230mm angle grinder disks [and some 125's].

Is there a difference? grit size? More importantly, cutting speed.
Table saw is about 5000 rpm, angle grinder 6600, the wheel wouldn't be run over spec but I'm not sure if the speed would suit carbide grinding.

What about a smaller [125, 5" I think] wheel in a bench grinder for tool bit sharpening?
They sure are cheap and easy to get compared to the purpose made ones.

[juiceclone]

I have a small diamond wheel on the same shaft clamped alongside of the green carbide wheel.. The grit is coarse and leaves lines in the carbide that require going over with the green wheel. That said, the diamond cuts fast and it's just a cheap HF one so easy replacement if necessary. Lets u fix those chipped carbides easily that might have been thrown away otherwise.

[liveaboard]

I made the necessary adapter and jig, and tried it for myself; as you can see from the attached photo, the result was disappointing.
Pointless, that is, the edges were left without points...
This was a fine grit 125mm [5"] masonry diamond cutting disk for an angle grinder. RPM was 4000, so surface speed was about 1,500 meters per minute, or 5,000 feet per minute.

The wheel is far too rough; you can see the deep grooves and chipped edges.
So now we know!

[Harold_V]

I fully expect that the diamond in the wheel is set in a metallic matrix, which isn't acceptable for fine grinding. They generally don't run true, and are prone to chipping carbide, as you discovered. Beyond that, the diamond bits are too large, so you can't achieve the desired finish of grind.

Diamond wheels used for grinding cutting tools are generally bonded in a resinoid matrix. While my opinion isn't any better than those of others, in my world, a wheel coarser than 200 grit isn't acceptable for sharpening carbide. I am currently running a 220 grit, which I consider acceptable for both roughing and finishing for turning tools.

A comment on the use of silicon carbide (the green wheels).
After leaving the missile industry, I worked in a shop that used a lot of brazed carbide, but never used diamond wheels. As a result, I was forced to grind with the green wheels. From that experience I learned that they are borderline acceptable for grinding, and nothing more. They are not hard enough to perform the required task properly, so they simply "club" off the carbide, or, said another way, they chip it away. That being said, using one to "smooth" carbide that has been ground with a coarse diamond wheel is likely not as good an idea as it may appear. The resulting edge will be woefully lacking in quality, the lesson I learned by being forced to use green wheels. They will NEVER be an acceptable alternative to diamond.

Harold

[liveaboard]

You're quite correct, it's a metallic wheel. I've just ordered a 180 grit resin wheel [I didn't find a finer one] , but don't know if it will be thin enough to get in and cut the face of the teeth on the saw blade.
I know normally the teeth are ground on the outer surfaces, but that's difficult...
Those drycut steel blades are expensive and I've been unable to locate anyone with a suitable sharpening machine withing 500 miles of me.

[Harold_V]

If you must grind the face, take extra care to not alter the rake angle.
The 180 grit wheel will do an adequate job, although with a slight compromise in finish.

Be aware that the wheel most likely should NOT be used dry.

And, avoid contact with steel, as that dulls the diamond rapidly, assuming you're running the wheel at acceptable speed. Steel dissolves diamond if it is in intimate contact at high temperature. The diamond (carbon) is absorbed by the heated steel.

Harold

[liveaboard]

Thanks, I hadn't considered that the wheel I ordered might need lubricant.
I have no way of using it wet. The wheel costs about $10 including postage from China; A machine capable of spinning in in the presence of water will not be so cheap.
I'll just have to give it a try, and avoid overheating if possible.

[ctwo]

And, avoid contact with steel, as that dulls the diamond rapidly, assuming you're running the wheel at acceptable speed. Steel dissolves diamond if it is in intimate contact at high temperature. The diamond (carbon) is absorbed by the heated steel.

Harold

Are diamond impregnated metal sheet plates, generally used for sharpening knives, OK to use for hand honing carbide cutting bits? The ones I have are the type usually used for knives, but without any hollows. I think they are 400 and 600 grit. I assume I do not need to worry about steel contacting the diamond dust with hand honing since temps should be cool.

[Harold_V]

I have limited experience with the use of diamond on steel at slow speeds and low temperatures, but it is my understanding that it will perform without issue. Heat is the problem, even with coolant, as the point of contact is still very hot, and that's when the damage appears to happen.

I've witnessed how quickly a wheel loses its ability to perform when I have not relieved the steel adequately when sharpening brazed carbide lathe tools. Once dulled, the wheel demands dressing, which is accomplished with a fine dressing stick. It's hard to determine how much is the exposing of new diamond bits as opposed to eliminating loading of the wheel, but, regardless of why, the improvement in performance is quite noticeable.

Harold

[liveaboard]

I have successfully touched up a carbide router bit with a diamond file.
It's slow going, but it works.

[duckman903]

When we sharpen our carbide scraper blades our lubricant was just a little kerosene on a rag that touched the wheel.