I've Discovered the Secret to Cool Grinding

other solutions, proper wheel selection

bill tindall

>I submitted an article to the Articles section on this topic ages ago. Hope to see it soon?

The "secret" to cool grinding is simply proper wheel selection. In production situations they worry about wheel life, but wheel wear is something us occasional grinders need not be concerned with. As a result we can use the coolest running wheels available.

I routinely grind right to the edge of my tools with an 80 mesh wheel running at 3600 rpm and I get no burning.

Most of the heat generated in grinding can be removed with the chip formed by a properly cutting wheel. If the grit is sharp, a chip will be milled out and much of the heat generated in forming this chip will be removed with this chip. A dull grit ploughs through the metal leaving much heat behind.

So, how to maintain sharp grits? Use a friable grit and a "soft bond. For finish grinding hard tool steels a pink wheel is best, with white second best. And, buy the softest bond you can find, with H recommended and J acceptable. For heavy grinding where there is more pressure available to fracture grits, other "colors" are better-ruby, blue, ceramic. For more information, wait for the article to appear.

Re: other solutions, proper wheel selection

Rick Hoppe (Los Angeles)

>Bill, thanks for all the detailed info. I look forward to your article.

Re: other solutions, proper wheel selection

Joel

>Bill take a look at the new Norton 3X blue wheels - they are the consumer version of the SQ wheels which run cooler than anything I have used.

You ar right about having sharp grit on the wheel as very important. Dressing a wheel frequently keeps everything sharp.

I can now grind a chisel typically in under a minute with no burning on a 3600 RPM 6" grinder.

Re: other solutions, proper wheel selection

Lyn J. Mangiameli

>I have two sets of these 3X SG wheels. One on a 6 inch high speed grinder, and another set on an 8 inch slow speed grinder. I've had them for too little time to develop a detailed appraisal, but initial impressions are very good, for both grinders. The only thing I've been dissatisfied with till now is that all of mine do not have very good balance, and can really use a Oneway Balancer, which adds to their expense. Fortunately, the ones I have all have a 1 inch bore, which can accept the Balancer--an improvement over the original SG wheels which I could never find (via Packard and Craft Supplies) with a bore large enough for the Oneway Balancer. Nonetheless, very cool and very sharp for a dry grinding wheel. I have only 46 and 80 grit sizes, and would be interested to see how a 120 size would do with respect to heat.

more on wheel selection, friability

bill tindall

>The following is from extensive discussion with the technical staff at Radiac (which may be the only US manufacturer of abrasive wheels) (Nice folks)

There is a factor on wheel selection that is seldom discussed and that is how much material does one wish to remove with a pass across the wheel. The lighter the pass, the less pressure to fracture the grits to expose new edges. Hence, for light pass finish grinding one wants the most friable grit available.

Blue, Ruby and Ceramic grits are for heavy material removal so these are less friable grits than white or pink which fracture more easily. These grits are more suited to initial tool shaping, while white or pink is better suited for cool finish grinding. Pink is harder and works better on things like the 3V tool steel.

I have been using the pink RAA H bond wheels from Radiac and I get no edge burning even at 3600 rpm. I'm delighted and can't see where I could get any improvement. The Norton equivalent would be 25A with a VP2 bond, and Norton recommends such a wheel for coolest finish grinding on hard tool steel.

why 120 grit?

bill tindall

>A diamond hone, or 15 micron diamond powder on a substrate, promptly removes even 60 grit scratches for tool steel. Because you are in the honing camp, there would seem to be little benefit from going to a finer wheel grit, except slower material removal(better control).

the Norton ceramic wheels excell in heavy material removal while providing long wheel life. Neither of these benefits seems worth the premium price for routine tool sharpening (unless one is in the tool shaping business, like the person that first advocated these wheels to the turners).

Balance: the balance, or lack of, is most likely in the bushing. The plastic bushings are quite prone to causing balance problems.

Re: more on wheel selection, friability

Joel

>Bill,

I'm surprised that you say "Radiac (which may be the only US manufacturer of abrasive wheels)" Norton wheels are also made in the USA - certainly their 3x wheels. (norton is owned by St. Gobain Abrasives but they manufacture in the US most of the stuff we use).

"Blue, Ruby and Ceramic grits are for heavy material removal so these are less friable grits than white or pink which fracture more easily."

I was involved in the testing and specficiation of the 3X wheels. What makes it a blue SG wheel is the abrasive not the hardness or friability. We spent a lot of time testing different combinations of abrasive and hardness and friability to get the right mix. The 3X wheels are very friable - and kind of soft. Maybe even too soft for some tastes but thy run very cool which was the most important criteria that we wanted. They do differ from the industrial SQ wheels which are used in surface grinders.

Re: why 120 grit?

Lyn J. Mangiameli

>It's due to my situation as a woodturner as well as a general woodworker (much like you), and not a general need for flat woodworkers. Specifically, I'd like the 120 for some small hollowing tips and rapid but finer sharpening of roughing gouges when chewing them up on bark and rocky roots.

For flat blades I agree with you about better means to get more refined edges after the coarser stones.

You commented:

"the Norton ceramic wheels excell in heavy material removal while providing long wheel life. Neither of these benefits seems worth the premium price for routine tool sharpening (unless one is in the tool shaping business, like the person that first advocated these wheels to the turners)."

Of course that is exactly what I want them for. I maintain nearly all of my woodturning edges on the Tormek. It is for rapid tool reshaping of "exotic" steels that I am evaluating them. There is also the matter that they hold their shape when dealing with round tools better than the super soft binders which are not a problem for flat blades, but can groove awful easily with things like gouges and small hollowing tips.

As for the balance issue with the Norton 3x stones. They are out of balance when no bushing is used at all, or with the excellent iron bushing that comes with the Delta, and even with the collar/bushing set up of the Oneway Balancer, so I think it quite fair to say it is in the wheels. One 8 inch wheel wasn't able to be fully balanced even by the two adjustable screw/weights usually used with the Oneway balancer. I like the wheels overall, but I'm not pleased with the balance.

One thing I'd add to this discussion is that color is not a reliable way of distinguishing between wheel types/functions. It is usually just a colorant added to the binder and could be easily changed (and thus manipulated if a particular color of wheels became prefered). Grey and white tend to be the natural color of some of the more common abrasives used (silicon carbide and aluminum oxide), but much beyond that, color is a characteristic of the binder more than the particle.

Re: more on wheel selection, friability

Lyn J. Mangiameli

>As many my now, the Norton parent company is French.

My 3X wheels, which are from relatively early samples if I understand correctly, are in packaging that shows them manufactured in Mexico.

The 3x wheels are a lighter blue than the earlier SG wheels. I got the impression this color was chosen rather than dictated by the SG abrasive. If not, it would imply that the 3X wheels have few SG abrasive particles in them. This may or may not be the case. If I remember correctly (and I don't swear I do) all SG wheels are not pure SG abrasives but have some aluminum oxide mixed in.

I'll be happy to be corrected if I am remembering/understanding an of this incorrectly.

Curiosity Perked.....

bill tindall

>What Norton product designation are you talking about, 3SG? I was unable to find anything in the Norton Literature, or other manufacturers cross references, to the numbers and letters you refer to.

I think SG is aluminium oxide

bill tindall

>I believe the SG abrasive is just another form of aluminium oxide, the SG (seeded gel) describing the colloidal process by which this aluminium oxide is formed. There are varients of SG abrasives that have "ruby" and zirconium added.

Re: more on wheel selection, friability

Joel

>You might be right on Mexico - I don't remember looking at a recent package. We have been selling them on-line for over a year - now the additional grits (mostly for turning) are coming on line - and the one I actually use on my grinders are various protoypes which were domestic. I have to look at current packaging but it makes sense to move them to Mexico where a lot of the consumer stuff is made.

So I guess I'm wrong

order a custom 120 wheel from Radiac

bill tindall

>I thought you honed lathe tools, hence my question on the 120 grit.

Radiac will make a custom wheel anyway you want it. The $$ premium over a stock wheel is only about $10 in lots of 5 and almost same as stock price in lots of 10. For small things a 1/2" wheel could be adequate and they are very cheap. With your recommendation, selling the extras would not be a problem.

In the 120 grit you will be doing light passes so it would seem that my original recommendation of a pink RAA bond wheel would be optimum. As far as I have ever read, the SG (which Radiac makes also) wheels show their advantage for heavy stock removal. I can tell you that the pink cuts 3V like butter in 80 grit.

I will bet that the artificial water stones are simply an extremely friable wheel grit, for example "friable white" with a porous bond. I have considered having Radiac make me a flat white stone in the RAA bond to see how it performs. Hand grinding provides very light pressure for grain fracture, so a very friable grain would be necessary. Couple this grain with a soft porous bond and I'll bet you wind up with a synthetic water stone, probably invented by a woodworker working in the grind stone development lab.

Re: Curiosity Perked..... *LINK*

Joel

>They are a called 3X wheels. THey are sold by the consumer division of Norton. THey are consumer repackaging of the SG technology - which has been around for a bunch of years. We have been selling them for about a year - and now the range is being expanded. I have to check with Norton to see if the they retain the traditional gradings - I'm not sure if they do. They are the coolest running wheels I have ever used.

heres the link:


Norton 3X Wheels

Re:origin

Lyn J. Mangiameli

>Mine show on the label what I think is a 10/04 manufacture date, so likely they came after yours were made up. I imagine you were right that the prototypes were formulated in the US and then outsourced for later production. Good for you for having a hand in making these available and affordable.

Re: Curiosity Perked.....

bill tindall

>The link you provided to your store didn't provide additional information as to the Norton product code for the wheel in discussion.

Try the Radiac pink in a RAA bond for coolness. I can grind right to the edge of a carbon steel plane iron, 80 grit, 3600 rpm and get no burning. There is no need for me to do better, if there is a better.

I can get a stock wheel from Radiac in 3 days, not much longer on custom order, so you would never need to be out of stock if this was your source. I'm confident they can make a Norton equivalent.