I promise this post is not about sharpening. It is, instead, about what we read vs. what we see.
When I learned to sharpen, the entire first day of my lesson was all about flattening the backs of my chisels and plane irons. I was told to get them all dead flat and then polish them up like a mirror. It was a whole damn day of my life I wish I could get back.
When I started buying vintage tools, however, I looked at the backs and thought: I don’t think those people had the same teacher. I’ve examined hundreds of vintage planes and chisels, and I can recall only one or two that had the backside of the blade flattened or polished.
Sure, some of them looked like they had been pushed over a stone to remove the wire edge after sharpening the bevel. But not flattened and polished like I was taught.
Most 20th century instructions don’t talk much about the backside of the tool. You are supposed to work the bevel and then remove the wire edge by rubbing the back flat on the stone. (The Stanley instructions above are typical, which are from a 1941 booklet.)
Joseph Moxon, who wrote the first English instructions on woodworking, discussed this issue in “Mechanick Exercises or the Doctrine of Handy-Works” (1678). He wrote that after you sharpen the bevel of the tool:
“Then turn the flat side of the Iron, and apply the Stone flat to it, till you have worn off the coarse gratings of the Grindstone, on that side too.”
Basically, you have to stone the bevel and the back. The instructions were clear in the 17th century and they are clear now. So why does the archaeological record – at least what I have seen – seem at odds? Why are there so, so many tools out there that have been sharpened on the bevel but not on the back?
I think about these things a lot as I work at the bench. And I promise I do not have any answers. Only thoughts. Here are a few of the possibilities I’ve considered.
- Perhaps most of the extant old planes and chisels were used for carpentry (in softwood) or by homeowners. So getting the wicked sharp edge needed for tricky hardwoods wasn’t necessary. So the back remained mostly untouched (except for removing the wire edge).
- Furniture makers need a really sharp edge, but that profession has always been a less common one than carpenter. So the well-treated tools are much less common.
- The good tools that were sharpened properly were mostly used up. The tools that weren’t sharpened properly survived because they weren’t used much (perhaps because they weren’t sharp).
- Modern people have a much more extreme idea about what a polished edge should be. We take it beyond what was typical because we have the abrasives to do it. A mirror polish might be better in theory but it might not be necessary in actual practice.
- The user decided to go for a flat and polished back in a gradual fashion – by stoning the backside over and over as they sharpened the tool during the day/month/year. In other words, the tool would get gradually better over the life of the blade.
- We are too precious about our finished surfaces. A few errant grinding marks on the backside that transmitted to the work can be easily scraped or sanded out by hand.
I have a lot of other possibilities rattling around in my head, but the above six are enough for a blog entry. During the last two years I have been experimenting with these different possibilities with my own edges. I’ve learned some things that are definitely not doctrinaire with modern sharpening theory. But I’ll save those for when I’m ready to endure an old fashioned Internet thrashing. Today has been too much of a Monday.
— Christopher Schwarz