Shannon Rogers interviewed me a few weeks ago and in the interview I mentioned my disdain for certain chisel sizes. Specifically, I said that students who come to woodworking classes armed with the standard set of 1/4″, 1/2″, 3/4″ and 1″ have four chisels all of which are the wrong size. OK, that’s a bit of hyperbole. But how much, exactly? Several listeners have asked for more detail about this, including Shannon, and I thought it might be helpful to type my thoughts on the subject here. You probably shouldn’t be surprised to learn I’ve given the subject a lot of thought. Lacking power tools, I rely on chisels heavily.
Many many students are chopping dovetails in woodworking classes. And unfortunately, woodworkers have placed an anachronistic value on what they call “London Pattern” dovetails. More about that some other time. When working a narrow range of thickness of wood, with a narrow range of dovetail angles, the resulting chisel width required is also limited. For 1/2″ stock, and depending on your chisel’s pattern, it’s possible 1/4″ may be slightly too big to get a really narrow pin. Honestly, this isn’t too big a deal. I’ve long advocated sizing your dovetails to your chisel. It may be that the 1/4″ chisel is one of the more useful sizes in your set of four. I have what Benjamin Seaton would call a 1/4″ “bare,” meaning a chisel slightly under 1/4″. I have found this tool helpful.
For 3/4″ stock, like that used in many or most classes, you really want a 5/16″ chisel. A 1/4″ chisel is too small and a 1/2″ chisel is much too large. At the very least, a 3/8″ chisel is helpful. In general, when chopping dovetails, I find having a few chisels of around 1/4″ (both oversized and undersized) and a few of around 1/2″ is helpful.
So what are my recommendations for a set of chisels? I think Lie-Nielsen had the right idea in offering a set of four as 1/4″, 3/8″, 1/2″, and 5/8″. That make a lot of sense to me. But I think it would be great to have 3/16″, 5/16″, 7/16″ and 9/16″. In many ways, I think I’d like those more. Again, if you are following me, it has to do with what you actually need in real-world use. Not surprisingly, we encounter a fairly narrow range of joint sizes based on our stock size.
In addition to that is the concept I call “The Cooperative Workshop.” In this concept, I’ve discussed the need for tools to help each other, chisels matching plows, mortisers, dado planes etc., and for plow irons and mortisers to be one-third of standard stock thicknesses. For this reason, I struggle to recommend metric chisels like the oft-recommended Hirsch firmers.
Hirsch chisels are available in a range of (metric) sizes. I’ve seen (and purchased) a 2mm, (completely worthless tool), 6mm (a reasonable 1/4″ bare), 10mm (too big to be a usable 3/8″ but too small to be a usable 1/2″ bare), 12mm (a reasonable 1/2″ bare) 16mm (very close to 5/8″ and helpful. Let’s call it 5/8″ full), 20mm (too big for 3/4″ dados, wider than most stock) and 26mm (larger than 1″ and can be useful but otherwise holds no real advantage over a 1″ tool). Metric chisels can be a good source of off-sizes (full and bare is the 18th-century lingo for slightly more than and slightly less than), but I certainly could never live with them as a “standard” set of chisel. Most egregious are the sellers who list metric tools only in approximate inch “equivalents.” I guess this isn’t so bad when selling carving tools. Otherwise, list the metric sizes. Americans really can divide by 25.4.
My much-maligned set of four (1/4″, 1/2″,3/4″, and 1″) also presupposes that the chisels in that set are in some way related. They often share design features including handle shapes and sizes but especially blade shapes (patterns) which I feel are inappropriate. My “Chisel Physics” (my term for my understanding of how chisels ACTUALLY work as opposed to how we THINK they work) suggests that in use, the 1/4″ chisel is nothing whatsoever like the 3/4″, let alone the 1″ tool. In use, the pressure you can apply to wood is very different depending on the width of chisel you hold. This causes the wood to behave differently and results in a different user experience.
I advocate that chisels be sharpened, certainly in accordance with their function, but also with respect to their size. Small chisels, 1/4″ and under, are essentially punches. A sharpened nail will likely hold its edge as well as any given 1/8″ chisel. And virtually any bevel angle will work (including 90° bevel angles) for many jobs. I find 1/2″ chisels to be particularly sensitive to bevel angles. These dovetail workhorses see a great deal of use and are the toughest to sharpen correctly. Large chisels, 3/4″ and above, offer so little pressure for most jobs that they can be ground back, with fairly low bevel angles.
Now just to head off my Australian friends at the pass, my sense of chisel physics assumes the use of Eastern U.S. cabinet woods: cherry, walnut, tulip poplar, cedar, and – though it’s not local – mahogany. Interestingly, the toughest wood on my chisels is pine. If you’ve followed my logic so far, you instantly know why. The hard/soft rings of pine, especially quartered pine (the use of which I advocate), poses a unique problem for an edge tool. Pressure is concentrated discreetly, instead of spread evenly across the cutting edge. And I believe that the hard parts in pine are pretty darned hard compared to other woods (like those previously mentioned), but I don’t know that for sure.
So the moral of the story is, when it comes to chisels, size matters.