For many people, chisels are handy little tools...for prying open cans of paint, that is. But a properly-honed chisel is an extremely useful woodworking tool.
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!
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!
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There are numerous ways to sharpen chisels. Some do it strictly by hand, while others use a jig. Some sharpen with oilstones, others with waterstones, and still others with diamond stones. Some use a strop at the end. This instructable will demonstrate the use of waterstones and a honing guide, and will get your chisel sharpened to 8000 grit with a microbeveled edge. Now here's what you need:
- 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.
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One small item that you forgot to go over that makes all the difference. Being a fine woodworker I am looking for the cleanest cut and the fastest sharpening time. Because of this I flatten the back and sharpen up to the final 8000 grit to a mirror finish before I do anything else. This sets me up for success in my sharpening. Yes, it may take a while but if it is VERY uneven you can even do just 1cm to 1/2 cm near the tip if needs be. Doing an inch or so will save you time in the future and will most likely last a good decade or more. Sharpening any edge too is reducing the material to an infinitely small edge by sharpening or "polishing". Any visible scratches are groves that will leave a serrated edge. The smaller the scratches the finer the sharpening possible. A mirror finish gives us microscopic scratches and a leg up in keeping a sharp tool.
After sharpening the back up to the 8000, I start on the bevel. 500 (or 800 or whatever) I run it over this level to establish a flat edge, create the geometry of the chisel and get a nice burr going. I then turn it over and with the flattened back I go to the 8000 (eight thousand) stone to "cut off" the burr. You will see it as a darker line on the stone until it disappears and evens out. Then back to the bevel next stone up. Same process and finally when I reach 8000 I have a chisel sharp enough to shave with.
This seems time consuming but with a little practice it won't take more than 5-10 minutes and leave you with a consistent result. Thanks again for the good Instructable!
I've since gone through all of them and given all of them a good resharpening, starting with the backs. I figured the backs would likely be a one-time endeavor, with me only needing to pay attention to the microbevel (and from time to time, the primary bevel as well).
Thanks for the suggestion.
http://a.imageshack.us/img838/5759/sideo.jpg
Skip the stones!
I use the Veritas sharpening jig. It has a roller on the back with an eccentric cam. Just turn the cam 90 degrees to raise the chisel up 1/2 degree for the micro-bevel step.
Once you get your chisel sharp, it is usually only necessary to hit it with a few strokes of the finest grit to "tune it up".
One of the very best ways to "true' your stones ( making them flat again is called "True'ing" them) is to pour some water on a flat concrete sidewalk, and work the stone on this surface.
I find a "figure 8" pattern is best.
This cuts the stone to flat very quickly and effectively.
Once it is flat, I then finish it with sandpaper, wet, on glass, as you described above. That is just to take out any scratches on the stone.
Sharper edges will bite on steeper slopes of your nail. But 45-deg is a pretty decent edge.
In my case, I bought a somewhat similar adjustable angle guide from "General" brand of tools that uses two small wheels that can roll freely at both sides of the sandpaper strip if you cut it a little wider than the blade to be sharpened, so that they don't have to roll over the sandpaper. Cutting the sandpaper in those widths gives several strips from every sandpaper sheet, which means even more savings!
To sharpen the narrow chisel blades, I made a wooden base with a lateral guide rail, so that the sharpening guide can roll straight and paralell to the sandpaper strip.
The glass plate is 3/8" (9 mm) thick, which is very rigid and ensures flatness even with some heavy down pressure; and was not expensive since the size is not large.
For me, the glass and wetordry sandpaper is the way to go.
amclaussen, Mexico City.
This is the original (a great read) on "Scary Sharpening": http://tinyurl.com/gcyg4