Sunday, September 7, 2008

Sharpening. What works for me.

Sharpening blades is a metalworking activity, and metalworking is what I do, and what I'm used to. At first I automatically gravitated towards diamond stones, because that's what I'm used to. I've got a diamond hone that I've had bouncing around in my toolbox for over a decade. Maybe 15 years, now. Still works great.
So when I got into woodworking I bought diamond stones, and used them, and liked them.
Then I needed something finer, so I bought ceramic stones. Again - something I was used to. I didn't want oil stones (which I'm also used to) because of the mess.

Eventually I got tired of hearing about how great water stones are and how they are the One True Path for sharpening, so I bought a few to try them out.

The following is about what I have, and what I actually use.

Firstly, here are my diamond stones. The small one is a roughing stone, 250 grit,
6"x2". It is rarely used.. it's only needed to fix a chip in a chisel or something like that. The larger stone is double-sided with 600 grit on one face and 1200 grit on the other. This is still my most-used stone, and if I had to have just one this would be THE ONE. These are DMT stones with the drilled sharpening plate, obviously. I like these a lot for plane irons and chisels because the swarf (that's the 'metal dust' that is abraded from the object being sharpened) falls into the 'holes' and doesn't cause scratches in the finish. These are not great for small gouges or small knives or anything else that will poke into the holes and get maimed. For that you want a flat, undrilled plate, which DMT makes as well.

Next comes my first polishing stone. This is a ceramic stone.

I like ceramic stones a lot because they cut fast, and will happily do the job with just a touch of lubricant, which can be anything handy. I use mineral spirits as the lubricant for both the diamond stones and the ceramic stones, because it evaporates and won't cause rust.

Here are the water stones. I've got two 1000 grit Nortons, plus an 8000 grit Norton. The reason I got two 1000 grit stones is so I could use Rob Cosman's method of keeping the stones flat. It works.

And here is my current sharpening jig which I use when grinding the bevel. I do
honing by hand, and I'll get to that in a minute, but I like the jig for getting the angle right on the bevel. I use the Veritas Mark II, and I have the cambered roller for lightly cambered blades (smoothing planes).

So what do I actually use? Good question. At first I used the jig on the diamond stones and was happy. The blades weren't really sharp enough at only 1200 grit, but most of the time it was actually just fine. When I needed more sharpness I bought the ceramic 8000 grit stone. It's too small to easily use with the jig, but I used it anyway and it worked.

When I heard the siren call of the water stones I pulled out the VISA card and bought them, took them home, and spent a weekend sharpening everything I owned. At first I liked them. I really did. If you're going to do a serious hours-long sharpening session, they work great. For touch-ups they suck. Why? Mud. They get mud all over everything. It's horrible. And if that wasn't bad enough, I found spots of rust on some of my blades the next day, and also on the bedding surfaces of the planes. I thought I'd wiped them off well enough, but I guess I hadn't. That wasn't a good morning for me. I wasn't happy at all.
At one point I considered using just the 8000 grit water stone, because it doesn't need to be soaked, just spritzed with water. I could use a diamond stone to keep it flat, and just leave the 1000 grit stones in the cupboard. Then I got wise.

I got myself a 'secret weapon'. Yes! Cast a loving eye on this beauty!
What? You expected high-tech? From the hand-tool-only guy? Nope. An elderly Craftsman hand-cranked grinder with a hard felt wheel charged with the green honing compound that Lee Valley sells. Oh, it's... it's just magical. I can take a chisel from the 1200 grit diamond stone, give it a quick hone on the hand grinder, and it is shaving-sharp. I mean, the unwary could shave clear down to the bone in a heartbeat. It's wicked sharp. So once in a blue moon I use the non-rusting-mineral-spirits-lubricated diamond stones with the jig to establish my angles, then I just buff the tool as required on the wheel. No need to remove the wire edge, either... it just 'vanishes'. When it's gone, you're done. You don't touch the back of the blade, you just hone the bevel. This thing works gangbusters for carving knives and whatnot.
Of course, 19 times out of 20 you just need to touch the edge to the wheel again to re-hone it. Re-grinding the bevel is a rare occurrence around here.
I'm considering making a grinder (yes, a powered one) that would have easily replacable wheels so that I could have different firmnesses of felt, or a buffing wheel, or different profiles (for gouges, etc.). I'm still mulling over the design.


Andy said...

Hi Mike
I have the exact same sharpening set up as you,(diamond stones, felt wheel with compound) the only exception is my grinder is a Delta variable speed. My problem is when I put a beveled edge to the felt it seems to round over the edge. Do you use a jig of some kind or do you free hand it on the grinder?
Also I'm having problems keeping the compound on the felt, from the look of your photos the compound has really adheared well to your felt, any tricks in that regard?
Andy in Sudbury

Metalworker Mike said...

I free-hand them. I use a *hard* felt wheel, not a soft one. That's liable to make a difference. I used to have a leather wheel, believe it or not, and that worked pretty well, too.
As for loading the wheel, there are two things that interfere with getting the compound to stick: The first is speed. Speed isn't a problem for me since my grinder is hand-cranked so I can run it as slow as I want to for loading. Since I can run it so slow I don't need to do anything else for loading, but if your grinder won't go that slow then you really have to worry about the second thing, and that is fuzz. The fuzz on the felt wheel will seriously interfere with loading. When you get a new felt wheel you de-fuzz it by passing it through a flame from burning newspaper or some other cold flame. You want to burn the fuzz but not cook the wheel. A propane torch could work if you closed the air gap so that you had a cold yellow flame instead of a hot blue flame.
Once the fuzz is gone then you can treat the surface with mineral spirits to soften it up temporarily, then you run the wheel as slow as you can and press the compound in. Once you have a good layer of compound on the wheel you won't have to worry about it any more - the new compound will stick to the old. Just make sure you keep the speed down and you should be good.