Diamond Grinding Wheels for a Tool and Cutter Grinder

[user 52078]

I have a small home built tool and cutter grinder. I have been thinking about fitting it with diamond wheels, mostly to avoid all the dust from dressing conventional grinding wheels. I would appreciate other's experience on the following points:

• What grade of diamond grit do others use. It is mostly for putting an edge back on end mills and occasionally drills.
• I have been told that steel and diamond do not mix as the diamond will migrate into the steel, so use CBN wheels. Only one snag - the price. Is this diamond and steel thing actually real on a machine that gets used once every few months at 3000 rpm? I am no spring chicken and I don't think I am ever going to see my money back by buying CBN wheels! But if it is really needed, then I shall bite the bullet.
• I am running a 5" wheel at 3000 rpm if that is relevant. I would probably also have a 4" cup or saucer wheel.
• I already have a diamond impregnated cup wheel, but the grade of grit is super fine and it really doesn't cut. Quite good at polishing, though. I don't want to make that mistake again.

Thanks in advance for any thoughts,

Martin

 

[mc_n_g]

Here is info directly from Norton on their diamond grinding wheels

100 Roughing. The most common grit size for roughing operations.
120 For roughing where 100 is too coarse. Also for cut-off applications.
150 Medium stock removal plus good finish. For combined roughing and finishing applications.
180 Medium stock removal plus good finish. To improve finish.
220 Finishing
320 Finishing
400 Fine Finishing
10/12 Mic Super Fine Finishing
6/12 Mic Super Fine Finishing

This all comes down to what sort of finish do you want. I have used 120 and 150 cups in the past on a Darex and have had no problems resharpening end mills. You will also pay different pricing between 1/16 and 1/8 thickness of diamond/cbn. As for the steel migration into diamond wheels, you are not in a production environment. Will the life of the wheel you buy see that much of an issue? I don't use my wheels enough in the home shop to really see a difference. I also don't want to steer you towards a wasted path. CBN will almost always be more of an expense. You can sometimes find them in surplus or used. Just make sure you look at the grit size. You should true up diamond and CBN wheels but I am guessing most home shops do not.

 

[user 52078]

Thanks mc_n_g,
That is the most concise answer I could ever have hoped for - manufacturer's information tempered with personal experience. I shall get on and purchase a couple of wheels.
Many thanks,
Martin

 

[clockworkcheval]

Stefan Gotteswinter has an instructive video on a slow carbide grinder with a fine diamond wheel:

.

I use myself the extra fine diamond wheel on my TORMEK slow watercooled grinder. Slow and watercooled protects the diamond layer against overheating which causes the diamonds to crumble. The results are very nice - the tooltips look polished.

 

[user 52078]

Thanks Clockwork. That is a very tempting build..............
Martin

 

[timo_gross]

I ruined the edge of one electroplated diamond wheel with steel grinding. (on the flat it is still good enough to be used)
I have the feeling it is also a heat related chemical wear.
If you do not "overdo" it with aggressive cuts. I would guess (not guarantee) diamond will be usable for quite a while.
The CBN wheel for my drill grinder was about 50 USD (smaller than 5" for sure) I feel more relaxed not having to fear damage so I swap the wheel between HSS and carbide workpiece.

The sales guy from a factory, making resin bond wheels explained to me the cheap chinese resin bond wheels have less diamond powder in the resin mix.
The price is also determined by the volume of diamond resin mix. (circumfence, width and thickness)
His conclusion was that a cheap wheel is not necessary a "fraud" it may work just fine for "low production" and an expensive wheel does not have to be a "ripoff".
If you use a resin bond diamond wheel, you can still reconsider if wear is an issue, it will cut HSS and it will not "explode" only wear out faster.

Greetings Timo

 

[awake]

I have a vague memory of reading that the problem with diamond grinding on steel is that, when it gets hot enough, the carbon (diamond) dissolves into the steel. Can anyone confirm or discredit this?

 

[clockworkcheval]

Maybe just a matter of semantics, but my memory speaks of 'crumbling into tiny particles'.

 

[petertha]

I have a vague memory of reading that the problem with diamond grinding on steel is that, when it gets hot enough, the carbon (diamond) dissolves into the steel. Can anyone confirm or discredit this?

I've read about wearing/degrading rapidly & potential chemical reaction at elevated temperatures. Usually the recommendation for steels is CBN. But I'm wondering the same thing for home shop use. Diamond wheels for TCGs are readily available & reasonably priced from typical Asian suppliers. Now are they real diamond despite the packaging label & what exactly is the temp limit of the matrix binder & does a home shop machinist typically encroach into these levels? If wearing them out prematurely was the only downside, they are still cost effective IMO. But if we are somehow adversely altering the cutting tool by using diamond, that's a different matter. I've asked this same question on other forums & have yet to get a definitive answer. What little grinding I've been doing, I cant see much wear or loading on my typical 'brown' diamond wheel. Most of the grinding Stefan.G & Robin.R show on their YouTube vids is on carbide blanks which is fine for diamond.

https://info.eaglesuperabrasives.com/blog/diamond-or-cbn-which-grinding-wheel-do-i-need

 

[timo_gross]

I've read about wearing/degrading rapidly & potential chemical reaction at elevated temperatures. Usually the recommendation for steels is CBN. But I'm wondering the same thing for home shop use. Diamond wheels for TCGs are readily available & reasonably priced from typical Asian suppliers. Now are they real diamond despite the packaging label & what exactly is the temp limit of the matrix binder & does a home shop machinist typically encroach into these levels? If wearing them out prematurely was the only downside, they are still cost effective IMO. But if we are somehow adversely altering the cutting tool by using diamond, that's a different matter. I've asked this same question on other forums & have yet to get a definitive answer. What little grinding I've been doing, I cant see much wear or loading on my typical 'brown' diamond wheel. Most of the grinding Stefan.G & Robin.R show on their YouTube vids is on carbide blanks which is fine for diamond.

https://info.eaglesuperabrasives.com/blog/diamond-or-cbn-which-grinding-wheel-do-i-need

The ones I have are labeled SD (synthetic diamond) price differences can be explained without suspicion.

• volume of resin mass
• content of diamond
• runout, balancing, size, accuracy of shape

, so I would guess most of it is diamond.
On the other hand I wonder how many CBN wheels are in fact diamond.

Yesterday I saw a lot of descriptions similar to this "CBN diamond wheel for knife cutting!"
Obviously the language is a little mixed up. Often just a matter of weird translations; not intentional.
Sometimes CBN diamond wheel means CBN or SD wheel and there are different options at different prices to choose from.
Sometimes diamond wheel just means resin bond grinding wheel. ( CBN? TV station? Chen Brothers Nantou? )
knife, blade, cutter seem to be all same in Chinese, so they are interchangeable.

Greetings Timo

 

[user 52078]

Thanks for the replies. I am reliably informed that Santa will be delivering a diamond wheel soon. I tend to go with Timo's assessment. We shall see. I will report back here as soon as I can detect any wear.
Martin

 

[NapierDeltic]

Hi,
I speak both from my experience and from info available on the net.

This is a universal HSS sharpening machine (on cheap side). It uses a diamond coated wheel. It is long time produced and sold under various brands.
So- yes, diamond disks are default for what you ask. It is made for sharpening knives, dril bits, scissors and so on. I have one and used it for both HSS and carbide turning bits.
The carbon diffusion is something that really happens: clockworkcheval (and all others) gave the right direction . The reaction happens at high temperature. Low speed and water cooling give the longest life (in industrial environment) . In hobby environment, not-often usage and low pressure guarantees long life.
In dental industry, diamond coated disks are since long used and I have used them since long on my Proxxon. Edge cutting wears it rapidly - it is a thin layer; speed is highest, local pressure is high, cooling is low through 0.5 mm -or less- thin metal disk. I cannot say which wears first; diamond or carrier. On the sides, tool life is much longer. Nowadays diamond disks are standard in shaping metals and high hardness materials in all Dremel/Proxxon kits.
These are my rough conclusions, but I consider enough for hobby workshop. Off course, refining gives best efficiency.

 

[william_b_noble]

I have a vague memory of reading that the problem with diamond grinding on steel is that, when it gets hot enough, the carbon (diamond) dissolves into the steel. Can anyone confirm or discredit this?

Use diamond for carbide. Yes it will be destroyed by steel unless you are careful to not let it get hot

 

[Steamchick]

Hmmm... Not a clue what I have. But I tried a diamond disc to cut a large steel shower cubicle (2mm enamelled steel) to get it out of the shower room.... A few inches of cut and suddenly it stopped cutting, edge glowed red - so I gave up and used a half-dozen carbide cutting discs. Obviously the wrong application..... enamelled steel, no cooling! Horrible dust: sharp and gritty from enamel (ground glass).
So "Take care". I use a cup shaped diamond wheel for carbide tip sharpening/finishing, as it is very fine. needs high speed and firm but gentle contact to avoid heating. But heavy/hot stuff still gets the regular blue carborundum discs for any steel stuff.
K2

 

[Steamchick]

Diamond disc is fine at slow speed, water cooled, on my ceramic tile cutter.
K2

 

[Joe]

Hmmm... Not a clue what I have. But I tried a diamond disc to cut a large steel shower cubicle (2mm enamelled steel) to get it out of the shower room.... A few inches of cut and suddenly it stopped cutting, edge glowed red - so I gave up and used a half-dozen carbide cutting discs. Obviously the wrong application..... enamelled steel, no cooling! Horrible dust: sharp and gritty from enamel (ground glass).
So "Take care". I use a cup shaped diamond wheel for carbide tip sharpening/finishing, as it is very fine. needs high speed and firm but gentle contact to avoid heating. But heavy/hot stuff still gets the regular blue carborundum discs for any steel stuff.
K2

Let me guess, you turned the shower off first.

John

 

[peterl95124]

my diamond wheel tool grinder runs at maybe 100 RPM and is always kept wet to avoid overheating anything (either the tool or the diamonds), its primarily for carbide but since its so low speed I also use it on HSS with no problems of the wheel ever wearing out, if you run at 3000 RPM you should only be using alumina (maybe CBN, I haven't tried it), and you won't be able to grind carbide.

 

[Steamchick]

Thanks Peter. I need to amend the speed of my diamond grinder (turn the wheel on the speed control!).
K2

 

[Steamchick]

CBN is not a US TV News channel, but Cubic Boron Nitride - for anyone interested.
https://en.wikipedia.org/wiki/Boron_nitride