Sharpening and resharpening chisels at a consistent angle

1 04 2010

According to the Internet, a sharp knife is a safe knife, and the sharper, the better. Some people like them to be literally razor sharp — sharp enough to shave with. (For reference, good knives, when new, are usually sharp but not shaving-sharp.) For me, as long as a knife is just plain sharp and can cut easily, I’m happy. Going the extra distance to make it razor sharp doesn’t make it perform that much better, at least for my purposes.

With woodworking tools, it’s a different story. A razor sharp chisel or hand plane lets you do things that simply aren’t possible with one that is merely sharp. Since wood fibers are much tougher than (most) food, having a really sharp chisel matters more than having a really sharp knife. With a chisel, it can be the difference between using a hammer and just cutting by hand, or between leaving a rough edge and a glassy smooth one. A very sharp plane can leave a surface that’s smoother and shinier than is possible with sandpaper.

When sharpening a chisel or plane blade, it’s important to hold it at a consistent angle so that the very edge of the blade doesn’t get ground down at a more obtuse angle, and so that you can assess sharpness by looking at how it reflects the light. If the surface is rounded instead of flat, the light doesn’t reflect off it all at once, making it difficult to tell if you’ve ground away all imperfections in the cutting edge.

Many expert woodworkers sharpen their tools by hand and have trained themselves to hold the blade at a steady angle. I’ve tried doing it this way, and I always end up with a blade that has a rounded profile. So I bought a cheap (about $10) honing guide. It holds the blade at a steady angle and has a little wheel that lets you roll it along a sharpening stone.

A chisel in the honing guide

The guide makes it trivial to grind the chisel at a steady angle, but it’s still a bit of work to set the angle of the chisel the consistently, time after time. What I did previously was this: put the chisel in, tighten the holding screw, then place it on a flat surface and check if any light is visible between the blade and the surface. If so, loosen the screw, move the blade, and do it again. Usually it took around three or four tries before I got it just right. And then there’s the issue of grinding the microbevel, which has an angle a few degrees steeper than the main part of the blade.

A microbevel in the chisel blade

The purpose of a microbevel is to speed sharpening — it’s much easier to grind just the first millimeter or so of the blade rather than the whole thing. Adding the microbevel requires moving the chisel in the guide. The microbevel is too small to test with the light trick, so I ended up just moving the blade in the guide a bit. Unfortunately, “a bit” isn’t very repeatable, and that results in more time sharpening to fix the inconsistencies.

One solution is to spend $60 on a Veritas honing guide, but I realized that there’s a much cheaper way to get a consistent angle, time after time. After setting the blade in place, I took a utility knife and marked the blade flush with the back edge of the honing guide. These guide marks make it much quicker to start a sharpening session, which makes them much more likely to actually happen. Just put the chisel in and line up the mark with the back of the guide. There’s no need to check for light under the blade, and the microbevel will be at the same angle every time.

Marking the chisel flush with the guide. (The utility knife is actually slightly off the mark in this dramatic reenactment.) The marks on the left are for the primary bevel, and the marks on the right are for the steeper microbevel.

Most new chisels, including this one, are covered with varnish to prevent rusting, and the knife will score the varnish. If the blade isn’t varnished, the knife won’t mark the bare metal very well, so you might need to make several passes for the mark to be visible. I’ve tried covering unvarnished metal with black marker before marking it with the knife. This made the marks more visible, but the marker rubbed off pretty quickly, so it’s not a good solution. It’s probably better to make many passes on the bare metal, or to first coat that part of the chisel with durable paint or varnish.

Gratuitous tool shot

Update: I learned of a better way to set consistent angles in the honing guide.

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3 responses

2 04 2010
Olly Parry-Jones

Interesting post with good information and some excellent photography.

Your method of scoring a line on the chisel face is unique – well, it’s not something I’ve seen before! A more common alternative is to make a series of ‘projection boards’ for various angles. Or, to take a single board and draw a series of parallel lines, referenced off of one edge; each line depicting a different angle setting.

See the following link for a picture of the projection boards I’m trying to describe:

http://woodbloker.blogspot.com/2009/06/wheeling-and-dealing.html

(Note – that is not my blog!)

Olly.

2 04 2010
winstonchang

Those projection boards are an excellent idea! It looks like they’d take a tiny bit of work to make them, but then they’d allow even quicker and more accurate angle setting. I’ll probably make some of my own.

9 11 2016
Tony Gold

Yes it is easy to make a wooden guide block for checking the correct projection from the edge of the honing guide just set the chisle in the guide and set it on a flat surface like class till the bevel is flat on the glass and fix it at that distance now all you have to do is set it on a offcut of timber and fix a stop block with screws at the edge of the blade now you will always have the same angle for the micro bevel just move the chisle back in the guide to lift it 4 or 5 degrees higher or check with a protractor do this for any angle you need look at lie nielsen honing guid vidio hope this helps

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