Sharpening a chisel is actually quite easy, especially if you use a honing jig. An initial investment of less than $150 will get you chisels, a honing jig and sharpening stones - all of which will likely last longer than you will.
When I was first starting out in woodworking, I assumed that the "sharp" chisel I brought home from the hardware store was ready to go. But just because something is sharp enough to go through your hand if you're not careful does not mean it's sharp enough to take on wood with nice results.
Chisels go through an elementary grinding when being made which simply gives them a beveled edge. Look at the second picture below, and you can see the grinding marks on the main part of the blade. When we're done, the cutting edge will be glassy smooth.
So let's get started!
Step 1: Items Needed
- Chisels: I recommend Irwin brand chisels (formerly Marples). Woodcraft sells a set of four for $39.99. This instructable will work for any chisel, but you might need to do it more often for the cheaply-made ones.
- Honing Guide: A honing guide keeps your blade at the right angle for sharpening. Those who are more experienced go by feel, and indeed you may try this, but I use a jig. The one I use costs only $11.99 from Woodcraft.
- Sharpening Stones: As I just mentioned, this instructable will demonstrate sharpening with waterstones. I use two combination stones (again, from Woodcraft), that take the sharpening through grits of 800, 1200, 4000 and 8000. The 800/4000 stone will set you back $24.99 and the 1200/8000 stone will cost $49.99.
- Nagura Stone: If you use a waterstone with a grit of 6000 or higher, you will need a nagura stone. The nagura stone creates the "slurry" that helps sharpens the chisel. The same link for sharpening stones above contains a link for the nagura stone, which you can buy for $9.99.
Step 2: They're Called Waterstones For a Reason
Step 3: Setting the Honing Guide
Don't worry too much about getting it micron-level accurate at this point. Just get it to where you think the bevel is lying flat against the stone, and tighten the honing guide screw to lock the chisel in place.
Step 4: First Passes at 800 Grit
Set your chisel (in the honing guide) onto the stone. Applying even pressure on the back of the chisel blade, and with your thumbs on the jig, give it about five or six passes, forward and back. Try to distribute your passes over as much of the stone as you can, so you don't end up with a big groove right down the middle of your stone. Grooves are bad.
Wipe the blade clean and take a look at it. You'll now be able to see where the blade is making contact with the stone, because the grind marks will be worn away there. If you need to adjust the chisel's position in the honing guide, do so. You want the chisel blade to be contacting the stone at least for the first 1/8". The more the better, but the first 1/8" is the most important.
Do this step a few times. In between each set of passes, do three things: wipe the blade clean, inspect your progress, and rinse the stone of the residue that accumulated on it.
Now move up to the 1200-grit stone, and then the 4000-grit stone. Once you start making some passes with the 4000-grit stone, you'll notice the blade really starting to shine.
Step 5: Using the Nagura Stone
Take your wet nagura stone (which should have been submerged along with the other stones) and rub the top of your 8000-grit stone in a circular motion. You'll see the slurry starting to form on the top of the stone.
After each set of passes, rinse the stone like you did with the others, and reapply the nagura stone.
You're almost done. It's time to add a microbevel.
Step 6: Adding a Microbevel
A microbevel (or second bevel) is just what it sounds like: a very small bevel at the end of your already-beveled edge. The primary purpose of this microbevel is to save you time. When your chisel dulls, you merely need to sharpen the microbevel instead of going through all of these steps from scratch. It will take several sharpenings before the microbevel has been ground more or less flat with the rest of the bevel; at that point, you will go through all of these steps again.
To put a microbevel on your blade, slurry up your 8000-grit stone with the nagura stone and put your chisel/honing guide onto the stone. Raise the handle of the chisel a tiny bit, and with a nice steady stroke, push forward to the other side of the stone. Pick up the chisel (don't draw it back on the stone), place it again on the near side, and repeat a handful of times. Each time, try to raise the chisel handle by the same very small angle.
After several sets of passes, you'll see a thin line on the end of your chisel blade. Job well done.
But wait! There's one more important step before you can pack your stones up and start hacking away at wood.
Step 7: Flattening the Back
To get rid of that burr, you'll need to flatten the back of the chisel. To do this, start with the 800-grit stone. Lay the back of the chisel against the stone and make several passes on it. The chisel must lie completely flat against the stone.
It doesn't matter how much of the back you place on the stone. You only really need the very end flattened, but the more you have on the stone, the easier it will be to keep the chisel flat.
Do several sets of passes as you did with the blade, moving up through the 4000-grit stone.
There. You now have a finely-honed and powerfully useful tool. Now go to this instructable to see what you can do with it!