Norton 3X postmorten

something does not make sense

bill tindall, E. TN.

>First some nit picking ......"The extra hardness of Aluminum Oxide may be a negative." Aluminum oxide is a softer abrasive than silicon carbide, but it is tougher so the particles don't crush in use like the more brittle silicon carbide.

"So, for hand grinding blades and chisels -- Silicon Carbide good, Aluminum Oxide bad. ".............99.99+% of all plane irons have at some time been ground with an aluminum oxide wheel, either in manufacturing or in some cases just before final edge refinement. Furthermore, most bench stones, including water stones, are aluminum oxide. Do you have any insight as to why aluminum oxide sheet abrasive would be unsuitable while these other aluminum oxide formats have proven to work just fine.

Any plans to test Zirconia sheets?

Wendell @ Murphy, TX

>Just wondering how Alumina Zirconia sheets and belts would fair in a similar test. The marketing hype claims Zirconia is "two steps removed from the hardness of diamond". I assume this means it is even harder than Aluminum Oxide. In which case would you expect to see similar results to your Norton 3x experiment? I'd be interested to see this test since I ofter "grind" an initial bevel using 100 & 120 Zirconia belts glued down to a piece of thick glass. Also would electron powered versus hand powered make a difference? I know people use belt sanders as grinders also.

Wendell

worked for me

bill tindall, E. TN.

>I sharpened with alumina-zirconia paper for some time before going to diamond. It lasts longer and cuts more aggressively than aluminum oxide paper in the coarser grits. It removed metal and made edges sharp. A description of what we did is in the Articles section. I don't doubt the data reported, but I do question its relevance to the way most people sharpen with aluminum oxide abrasives.

The next smallest grit in a sharpening sequence must remove the previous scratches/damage/whatever. If the grit steps are appropriately small success will be at hand. If the steps are big, then the next smaller abrasive particle needs to be particularly aggressive or the previous scratches (damage, whatever) will not be removed and the edge will not be sharp/robust/whatever. Big steps in grit size can be taken with diamond. If the metal is abrasion resistant big steps can not be taken with aluminum oxide and that may in fact be what has been discovered.

Norton 3X correction!!

Brent

>Bill is right, I misstated my conclusion.

What I should have said, as Bill noted, is that AlO is tougher (not harder) than SiC - less likely to fracture.

As well, my conclusion does not apply to AlO in general, just to the variety tested. The problem may be the "open coat" style of the abrasive.

So, the conclusion should have been - Norton 3X 60 grit no, Norton SiC coarse benchstone yes.

As to further testing, I now have some 3M 80 grit SiC (thanks Joel) that I will test. I have some Zirconia belts that I may test after that.

Re: worked for me

Wendell @ Murphy, TX

>Bill,

Zirconia seems to work for me too. I do have problems with deep scratches if I skip too many intermediate grits. I am leaning towards not using anything coarser than 100 grit. For the way I sharpen, the speed benefit of coarser grits is negated by having to remove the deeper scratches. Especially since alot of times, I only figure I still have deep scratches when I am at the polishing stage.

The reason I brought up Zirconia was that fact that it should be even harder than Aluminum Oxide but it seems to work. So are the problems Brent is seeing with Norton 3X sheets related to the abrasive type, the product, or his methodology? I gather from his comment in his other post that he thinks it's something about the Norton 3X sheets in particular.

Wendell

could it be....

bill tindall, E. TN.

>That the problem created by the initial grit, Norton 3X, is not eliminated by the following step in your sequence. But, a different, may I say more commonly employed, sequence might overcome this problem. ?. What I am trying to say is that while the problem you discovered is fatal to your overall sharpening sequence, it might not be a problem to others.

I can't imagine that you can do more damage to an edge hand rubbing on paper compared to grinding on a 60 grit wheel, which I have done routinely. The difference is that I (and I suppose others) see to it that this damage is removed by the next step in the sequence. This, of course, requires that this next step be effective in removing adequate metal, which can be problematic with abrasion resistant steels and small grit sizes.

It would be of interest to compare your results with a 60 grit wheel vs the sheet abrasive. I'll stake you a lunch the next time I am in the NW that there is no difference and the reason the rest of us don't have a problem is that we remove more metal after the 60 grit. (In fact I have gone to 80 and now 100 grit wheel so that I don't have to remove so much metal).

The 80 grit silicon carbide experiment is going to be confounded by the fact that 80 grit silicon carbide is going to crush quickly with tool steel. Hence, you will be finishing the sharpening with something less than 80 grit, which will be similar to adding a smaller aluminum oxide step in that experiment. In my hands silicon carbide in coarse grits has a uselessly short life time grinding away at tool steels and hence is not recommended for this application.