Hand Tools Archive

Subject:
Re: less work

David Weaver
convex bevels all on one work well for an edge that never gets damaged.

Once there's damage, then you're into working the entire bevel and what the microscope shows me with full bevel methods is little damage that's never completely removed.

I'm going back and forth between just hollow grinding and then performing a small "lift" on the final bevel to make sure it's been worked by a fine stone, and going toward how I've seen some vintage professionally used tools set up - which is a relatively long shallower primary bevel and the convex part is just a bit.

I can guess why this was for two reasons:
1) someone using a plane on site wouldn't have to work through much if they damaged an edge a little bit, but a some point, they would have to put in considerable effort to reset the long bevel (presumably not while doing paid work)
2) it's fast for sharpening in general, you can use a single stone and still have a fine edge whereas something like the washita is pretty marginal sharpening a full bevel on harder chisels by itself.

Some of this started about 6 or 8 years ago when I was buying planes to use to see what I'd want to copy to try to make a good plane. One of the planes that I received was barely used and it had a huge long thin primary bevel on it, and the last bit of the edge was maybe (guessing) a millimeter long - steeper and more like what we're used to. I thought for sure it would break off, but in use, it didn't. It was very deliberately done (and unusually not ham handed off by a later less skilled user) and crisp.

Always a chance that i'm going down the wrong road.

As far as knives go, it depends on what knives are being used for. If they're for slicing, the whole action is a lot like paring and planing. What tests well for knives seems to work well for planing and paring. Mortising, maybe not so much.

People who like to scrape pipes or cut barrel lips - same thing - not so applicable. The razor as a whole, too - not that great for woodworking - we wear off in five minutes what is used in a razor edge in 2 years, but close up pictures across the bevel that show the rounding after stropping with linen and leather (something you can't see even with a flat metallurgical strop) make some sense in this.

It's common now (good leather and linen aren't as common) to use oxides and leave a gleaming flatter finished bevel, and the sharpness/keenness isn't really necessary. I always noticed that a linen and leather edge seemed to last all year if you really want it, too, but didn't figure as much rounding was going on as there is in pictures. Without it, the razor edge is more transient. Too much of it, the razor edge is blunt.

https://scienceofsharp.files.wordpress.com/2014/04/stropped_100linen.jpg

this is an extremely highly magnified image, this is at half as much magnification:
https://scienceofsharp.files.wordpress.com/2014/08/fusion_10kx.jpg

The top edge is a straight razor. I think the bottom one may be a coated DE blade.

While not directly applicable to woodworking, the issue is the same - the failure point in an oxide edge is deformation of the very edge. Spectacularly sharp for a shave or two (and I've noticed over the years that an oxide edge on a hard razor isn't preserved on linen - I think it gets rubbed off, so when I sell something like a kamisori, I don't use it on linen).

The razor done in the first picture on linen here has 100 strokes or so. I generally will do 50 a week. The edge is seemingly better for shaving a few weeks in than it was new (I think because it's probably more rounded, but not too blunt to easily cut hair).

Keeping the primary flatter in chisels and trying this stuff out has another side issue i'm wondering about - will it slip through material more easily without causing edge failure if the main part of a convex or flat bevel isn't there.

I have a steeper version of this from mortising cocobolo planes - but in that case, the regular bevel isn't steep - it's just "regular". the edge fails due to the hardness of the wood. If the whole chisel bevel is made too steep, it creates more physical work, but if just a little bit of the end is rounded over, it's generally easier overall to mortise than it was with a "normal" bevel because there's less edge failure.

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