Monday, June 26, 2017

Sharpening and Shaving

I remember one of the first woodworking classes I took years ago, a half-day on sharpening and using card scrapers. It began with a scintillating hour of the instructor, a graduate of a prestigious school, demonstrating his skill, in order to establish his bona fides perhaps.  Then we were told that every surface, the edges and the sides, of our scraper needed to be polished to a mirror finish.  We spent 2 hours on this highly stimulating task then, with an hour to go, we were shown how to burnish, waited our turn at trying and found that our results weren't great for some unknown reason or reasons.  As best as I can remember, none of us received any constructive criticism.  Then we were bid adieu.  Puzzled, I went back to sandpaper and I suspect most of the other students did too.

Polishing the sides of your scrapers to a mirror finish can be very useful, because that way you can use one of your finely honed plane blades to shave right in your workshop without needing a shaving mirror.  Which brings me to another subject.  I am happy if I can get my plane blades and chisels sharp enough that they will shave hair off my arm, which you don't need a mirror for.  I know that some woodworkers think this is not good enough and that the hair should "jump" or "fly" off your arm.  I once accidentally got one of my plane blades this sharp and it scared me.  I was afraid that a blade this sharp would make the shavings jump off the workpiece and hit me in the face or eye, and I don't wear a face shield when planing.  That could cause a lost time injury.

A while after the scraper class I took a class on sharpening plane blades and chisels taught by a foreman at a local high-end woodworking business.  He does all the sharpening for his crew.  One of the things he did was prepare a new chisel.  He flattened the back on a belt sander, went to a grinder to create the bevel he wanted and finished off on a diamond plate, all freehand.  The entire process took less than 5 minutes.  This class was at the opposite end of the spectrum from the scraping class; it emphasized the practical and wasted no time.   I don't recall a single jig. We all left with tools that weren't great but were usably sharp.  I do considerably better than this now, but it was a good starting point.

We all have to decide where we want to be on this spectrum.  Experiences like this turned me into a rather slovenly woodworker.  As a result, I don't flatten the backs of my chisels all the way to the handle, I use the dastardly "ruler trick" on my plane blades, I can't see my reflection in the sides of my scrapers ...  I could go on, but you get the idea.

In case you're wondering, I did eventually learn to sharpen and use scrapers.  When enough time had passed after the class for my inferiority complex to die down, I spent a few minutes watching Youtube videos, gave it a shot, then another and another, each time trying to figure out why things got better, or didn't.  Eventually I got the hang of it.  I really like scrapers now.  They usually make shavings but they aren't usable as shaving mirrors.  That's the way I like it.

There are woodworkers that are really into sharpening.  For some, it seems to be almost a meditative experience.  There is nothing at all wrong with this and I am in awe of them, in fact somewhat envious.  Really.  I wish I could lose myself in sharpening the way they do.  Instead, I ask myself whether the extra sharpness results in better woodworking.  How long do these superior edges stay sharper in practice?  I suspect not very long, but I don't know.

Calculus taught me to see processes in optimization terms.  As your tools get sharper your woodworking gets better, first rapidly, then more slowly.  You reach a point where extra effort isn't worth it.  That's my mental model, which has its own limitations.

As for classes, what you learn in classes is partly a function of the skill of the instructor as a woodworker and partly a function of his or her skill as an instructor.  This will sound arrogant, but I could teach a much much better class on sharpening and using scrapers than the one I took, even though I don't have near the skill with them.


  1. Interesting post. I agree on the instructor - just because you are a good woodworker doesn't necessarily mean you would be good at teaching it.

  2. there is an argument, which i cant claim to have seen evidence for, that sharper tools DO retain an edge longer because they have less flaws, which can act as stress concentration/nucleation points for further damage...

  3. You'd probably like the Marc Adams approach: to rehone an edge, he holds the bevel freehand against a belt sander for about 2 seconds which creates a burr on thr entire edge, then maybe 3-5 seconds on a buffing wheel with black rubbing compound, till the burr is gone. I'm not happy with my freehanding on the sander so I use the Veritas jig with a diamond stone, but then I polish on a cheap buffing wheel. The "woodworker pattern baldness" on my arm proves it's getting sharp. Some guys who know far more than me have conjectured that the buffing (or stropping) has much to do with the endurance of the edge.

  4. I didn't mean to imply that I prefer power sharpening, only to illustrate a point. In fact, I sharpen by hand except for occasionally reestablishing a primary bevel.