Hand Tools Archive

Subject:
before this gets too long (already did)..

David Weaver
..in the other post, more comments about mortising hard plane bodies because i have a lot of actual experience with it and plenty of failure to bring up.

It was popular when i first started woodworking to set a bunch of chisels up all the same, use them in a single task, and then declare the ones that held up less well as failures. I did the same thing and moved toward harder chisels.

When I started mortising plane bodies with a heavier chisel, then everything set up normally just didn't tolerate, and what i'd gravitated toward (japanese chisels - an imai timber framing chisel that I bought for planes in this case) set up at a fairly blunt bevel failed spectacularly. so I made it steeper until it tolerated the mortising and then eventually sold it. I tried it against an old american framing chisel (underhill or something) and that one held up as well as the japanese chisel but was less work to keep in shape (and less valuable) - they both did OK once the edge was rolled a little. A fatter bevel and the mortising became a lot more work, but a little bit of the edge rolled was good enough and it was easily reversed when done.

So I followed up mortising a plane with a cheap stanley 720, which didn't do well with a flat bevel, and rolled the edge a little on it, just a small one (perhaps another 5 degrees) and it also held up fine whereas using it with a flat bevel at 30 degrees or so was an absolute failure. Make the whole bevel steeper, then the mortising gets harder (probably due to friction or wedging).

I figured by the time I'd experimented with all of this stuff, the difference in where the good chisels tolerated mortising vs. the not so good was just a couple of degrees difference in the small roll of the edge.

I have a set of chisels (modern sorby) that don't hold up that well in hardwood, so I'm going to continue this experiment with them. They're soft. If you do pine drawers, they work fine, but even in cherry, they deflect easily and the edge gets bent up. If you increase the flat bevel angle enough to get them to hold up in hardwood, then you get the typical crushed fibers between the tails from breaking wood out instead of shearing it off. They'll be a good canary for this. Chisels that are too hard do the same thing, except they chip vs. deflecting.

I'm not really chasing anything here other than fiddling for my own benefit - it's not like the cap iron where I would tell someone else to do it.

I've learned over the years when someone says they're doing heavy work and their chisels aren't holding up to tell them to roll the edge over just a little bit and move on, though (rather than heading out to the internet to hunt down the the next chisel that costs 3 times more to do 20 minutes worth of work). Advice like that is usually ignored, though, just as newbies often do when they are asking which plane they can buy to work figured wood when they already have a bunch of common double iron planes.

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