Hand Tools Archive
.how much is enough?
just a little bit more.
When making the video about the unicorn planing (#2) I also planed with the cheap $3 buck iron on rosewood. I could see the silica, or so i thought, but there were no lines. So I didn't include showing that as I thought maybe I was making false statements and the dots were something else and not silica. but they sure did look like silica.
I couldn't leave well enough alone - is the method protective of the edge? It seems like it. It doesn't instantly feel like there's a clearance problem but what could be creating such a super bright surface. I think that is actually metal burnishing the wood and not just a clean cut. It's ungodly shiny. I did have a clearance problem when I just tried to buff an iron at normal angles (as in - if I just honed to 32 degrees or something that others would normally do and then buffed the edge, there was a serious lack of clearance and no self-downforce from the plane right from the start.
* washita back lapping, 32 degree microbevel (probably 3 hundredths or so, not small) on a 25 degree primary, 1 micron diamond, vs.
* unicorn ,washita back lapping, 20 degree primary
75 strokes on a rosewood plane billet (about 20 inches long). IT was dreamy at first. Super easy pick up of any shaving. Around shaving 20, the shaving split. Perhaps I left a bit of dirt on the plane. The rest of the shavings looked good. Another 20 more shavings and there were more smaller splits. OK, I wasn't wrong - it's silica. after 75 shavings, the undamaged parts of the iron looked OK, but there were dings as deep as about 4 thousandths of an inch. These take a long time to hone out and who wants to grind into the iron in the first place to get them?
I know I don't (vote for summer!).
There were probably 25 defects in the edge, these two shown were typical (I don't like to choose the worst - it overstates the problem). these are enough to make the iron not want to pick up a shaving very easily. The first ten or so were dreamy, though. In clean wood, dreamy would've lasted a lot longer.
The surface of the rosewood showed evidence of these, of course - the lines from the biggest defect were garish.
This iron is my mule (the first XHP iron that I made - same one used for both tests here), but we now know that at least some of the V11 irons are seen to be chippy in less than ideal conditions. In clean wood, this may not be a problem (I didn't have one). Less than ideal and these defects (including the one that was about four times as deep as the one shown above) have to be honed out. It hones half as fast. That's not cool. Since my testing where the king of clear clean wood was clear, i've come to prefer all of the rough work still with water or oil hardening steel.
At any rate, chase the primary back to 20 degrees, hone freehand to a pretty significant wire edge to get rid of the damage, and then lap the back.
planing rosewood with silica using the unicorn? can of corn.
The picture below is the worst of the damage in the edge after 75 strokes. The surface of the rosewood is bright and clear, no lines. The silica does not damage it. I have seen this in the incanel gouge, too, where silica will spider web the barrel of the gouge on the outside and not the edge. This is outstanding.
The trade off? The profile makes the iron feel like one of the first type (flat hone) that's planed about 100 feet of clear wood. It still picks up a clean shaving at the end of the board, but there's a slight difference in feel. The first iteration of this would've gone not too much longer before it became a pain to plane with because it can't pick up a shaving easily at the end of the rosewood billet.
This iron didn't pick up the first shaving as easily, but by shaving 20, they were a match. After that, it was no contest.
I have badgered most of the board with my fascination with preventing edge damage in irons because it saves time in the long run and makes everything more predictable. If you are a full bevel sharpener, and not just lazy like me - then this becomes critical because you will remove the damage you see but not the rest and you may make strange claims about the iron behaving poorly for a while. I have not noticed any such thing, but I have noticed that if I hone until I can see nothing at all, the peaks of the original notches will still be in the edge under the microscope. I know I drew some scuzz for using a 35 degree final bevel in the test irons to avoid having inconsistent damage.
This kind of thing is a pretty good illustration as to why that is. Even if you don't ever run into silica, you may run into dirt or something that's settled on wood at some point. If it's silica-based, this is what you'll get (top picture) and 32 degrees isn't any too little. I was able to plane much more in weight with the second iron with the same count of shavings because the shaving stayed smooth and continuous and didn't break apart.
You can see that the ability to continue with a clean shaving caused some wear on the top edge to start (it did a lot more work, probably double the amount).
I believe this protective ability, as well as the slight loss of clearance (which causes you to miss that first 50 -100 feet of super clean keen feel) -is why the dingy buck blade suddenly felt OK a few days ago. When I planed rosewood with it for a while, it showed no edge damage, and the same uncanny bright surface.
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