Primary bevels Norton 3X update *LINK*

Re: Primary bevels Norton 3X update

joel -( tools for working wood)

>Can you just clarify something?

Are you "grinding" using the 3X Sandpaper or grinding using a 3X Wheel?

The abrasive is completely different between them and it's confusing.

I grind using the 3X wheels to the edge all the time and then hone with no difficulty. I've never used the 3X sandpaper for anything except sanding wood.

For working a primary bevel by hand on sandpaper I would suggest the 3M non-PSA 80 micron film- it's closely graded and works real fast.

Bummer

bill tindall, E. TN

>Are you suggesting that the abrasive doesn't cut through the carbides, but wears away the iron matrix around them and they then fall out leaving a hole?

Popout mechanism

Brent

>I think the carbides are being popped out, not falling out when the surrounding area is worn away. Looking at the pictures, the surrounding area looks like it has been damaged as the carbide pops out, but is not otherwise worn down.

The images of the abrasives - in particular the very small number of particles per unit area with the 60 grit - suggest that very different things are happening with the open coat 60 grit abrasive.

There were some popouts during testing of some A2 blades - that is, during planing. In that case I think some different mechanism was responsible - possibly wear around the carbide, rather than a direct hit with a very hard piece of aluminum oxide.

The higher grit Norton 3X sheets have higher grit density. That may be enough to prevent this problem. More later.

Re: Popout mechanism

Joel

>the big coarse grit sparely spaced abrasives are hitting the carbides with lots of force are simply not sharp enough to cut the carbides so it pushes them and pops them out instead. With a finer or more densely packed abrasive you are taking less of a bite so it should work better but while I am looking forward to your retest on the D2 I think the problem is that the D2 is so tough that it is dulling the abrasive (which isn't that sharp to begin with) before the abrasive can do much work on the steel. I'd bet that you might get better results with a SC sandpaper on D2.

Incidently while I can see no reason for giving up my grinder a real application of this technology for my purposes is for flattening backs. It's pretty easy to lay down the paper on a flat surface and it's low cost of entry - which is very appealing - especially with such an inexpesive, readily available paper. So I am looking forward to your final conclusions and recommendations.

Re: Primary bevels Norton 3X update

Denis Ch�nard, Orl�ans, Ont.

>No disrespect intended, but I have to ask, why bother?

60X is awfully coarse for sharpening irons... I use a 120X wheel on my grinder and that works fast. But I don't like the hollow bevel the wheel gives, so I've bought the Viel sander that LV carries, fitted with a 120 grit blue zirconia belt (but I haven't had the time to try it yet).

Unless one has to do major reshaping to a blade, I don't see the point of going down to 60.

Then again maybe I'm missing something (wouldn't be the first time...)

DC

back flattening with paper abrasive

bill tindall, E. TN

>I have never successfully flattened a flat steel surface with a paper backed abrasive. I think there are others with similar experience. The leading edge always cuts more.

hollow objection?

bill tindall, E. TN

>I am curious why you dislike the hollow grind off a wheel. I see it as an advantage for honing after grinding but I may be missing something.

Re: back flattening with paper abrasive

joel -( tools for working wood)

>Is this with PSA paper or paper just held down with water or fingers? Ia long time ago I used sandpaper forbacks and I don't remember any problems but I can't say for sure. Now I use diamond laps on backs per your suggestions.

Why bother?

Brent

>Curiosity?

I had been told that 60 grit 3X worked well. Weeks later I saw some at the store and decided to try it, since I was already embarking on a test series that involved sharpening a number of blades.

It did work well, very fast - much faster than any other hand grinding abrasive I had tried. Looked like a winner. Turned out to be a loser. News to me.

However, I am still curious. So, I have some 100, 150, and 220 grit 3X (and may get some 80 micron 3M and I have some drywall screen somewhere) and will do some further testing.

If any grit turns up a reasonable balance of speed and edge quality, my curiosity will be well rewarded as I would prefer to not use a powered grinder. Expect to update the 3X pages later today.

In general I agree Bill, but

Wiley Horne

>one exception I have found is a 3M product. It's called 3M Imperial microfinishing film (PSA backed). The difference between this stuff and sandpaper (aside from price, which is considerable) is that the microfinishing film is backed with mylar. The PSA-backed mylar has no tendency to furl in front of the object you're flattening, and therefore does not round the edge. It leaves a sharp edge on a wooden plane, for example. The abrasive lasts much longer than sanding grit. I get mine from Japan Woodworker--undoubtedly many others carry it as well.

I would hasten to say that flattening things by lapping them always has potential problems. I mean if one is lapping something that is already flat, it will inevitably begin its journey into convexity. And if one starts lapping something that is already convex, it'll get more convex. Lapping works when the thing being flattened is slightly concave--that's why I like to scrape a hair of concavity into wooden plane sole interiors, whether they're Japanese or not.

Wiley

Re: Why bother?

bill tindall, E. TN

>For a year or more I ground primary bevels with 80 grit zirconia/alumina Klingspor PSA backed paper. On Carbon steels, eg Stanley plane irons and Sorby chisles, it removed piles of metal particles at amazing rates. If you have never tired it you will be surprised at how fast metal goes away with these less abrasion resistant steels. (you may also become surprised at how abrasion resistant some steels are relative to Stanley plane irons. I remain skeptical that sheet abrasives used by hand will wear away M2. My attempt at hand sharpening a set of M2 jointer knives remains vivid. )

Considering total time spent hand sharpening on the abrasive sheet was as fast as grinder grinding. Had I stayed with these tools I never would have considered a powered wheel grinder for this sharpening. Really, the only annoyance was the need to jig up the tool.

For me, power grinding on a wheel followed by hand honing (all free hand) became more universally applicable to all my tools and quicker.

Re: hollow objection?

Denis Ch�nard, Orl�ans, Ont.

>I agree with you that it does make honing easier, but my (maybe unwarranted) concern is that hollowing the bevel looks to me as being equivalent as using a thinner blade in practice, defeating the concept of using thicker blades for more rigidity and less chatter.

Then again, I do not claim any expertise in the matter, just a theoretical hypothesis.

DC