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Chisel Flattening

3K views 16 replies 14 participants last post by  dbray45 
#1 · (Edited by Moderator)
Guys -

I've been "honing" the poo out of this 3/4" chisel I got in a set from Wood River. I know there's better quality out there, but this is what I could afford.

Anyway, after going at it for 30 minutes with a 220 wet stone (that I just flattened) I still have low spots (see pic below). I've probably made a few thousand passes on the 220 stone. That's after about 10 minutes work on the (just flattened) 1000 stone, until I realized I wasn't getting anywhere.

Just so I can verify my technique, I'm letting the back of the chisel hang off the edge and putting all my pressure evenly, straight down on the blade. Every 50 strokes I rotate my stone to ensure I'm wearing it evenly.

A couple questions:

1. Am I doing this wrong, or is this normal?

2. Should I step down to 100grit wet/dry on granite like I use to lap my stones, or just keep going with the 220 stone? I'm not impatient (I find sharpening can be relaxing actually), but also don't want to be wasting my time if there's a better way.

Thanks guys! As always, as a newbie to this handtool/woodworking thing, I really appreciate your help and wisdom.

BW

Wood Tool Knife Metal Blade
 

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#3 ·
Also, I wanted to add that I leave a trickle of water running over the stone as I sharpen. I heard this was a good tactic, but now I'm wondering if it doesn't let the slurry build up on the stone necessary to do the sharpening work. Still don't know how "wet" the stone should be during sharpening.

Thanks guys.

BW
 
#5 · (Edited by Moderator)
Instead of wasting your stones on that. Get some 180 (or 150/120 or so) grit 3×21 belt sander belts from the local big box store, some spray adhesive and a real flat surface. Slice the belt at the seam ( and cut it in half lengthwise) and glue the belt to the flat surface.
Then flatten the back of the chisel. I use simple green ass the lubricant, ymmv.
Then go to the stones.
This also works well for rehabbing old tools, repairing really damaged cutting surfaces/edges and regrinding bevels when needed.
It is cheap and saves your stones for the fine work.
I use this myself and recommend it for my sharpening class as well as general sharpening advice, especially in tool restoration.
And like the others said, you are trying to flatten to much of the back. 1" to 1 1/2" is plenty.
 
#6 ·
Update:

So I think I found my problem. Cut off the running water and got a slurry going. Suddenly - my stone is cutting much faster (face palm). Forget where I read that you should sharpen under a trickle of water, but I don't think I'll do that anymore.

Thought it was kind of strange that my 220 stone was polishing…

Side note: I've had this on the stone for long enough that I'm starting to get some rust on the back where it's not contacting the stone (you can see it in the new pic). Should I just steel wool that when I'm done?

And what do I use to oil it?

So much to learn…

BW

Carbon Audio equipment Musical instrument accessory Microphone Bumper
 

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#8 ·
I have seen mention of leaving water running on your stones also. If I't not mistaken there was an article in Woodsmith magazine (could have been one of the others) in the recent past that had plans for making a japanese inspired sharpening station with a pump that circulated a trickle of water back onto the stone.
Not sure I agree with the method, and your results seem to prove that it was slowing you down!
 
#9 ·
Hmm, two things, 1, I learned something new from WhoMe regarding the sanding belts. 2, Wilbrijo gave it a good effort before asking and was polite thanking people in advance. Not many posters seem to appreciate all the good advice.
 
#11 ·
I wouldn't do this with a new chisel, but I've heard that if you are careful and your chisel is bellied, you can bend it ever so slightly in the middle. I've done that with some success on a plane blade; turned it into a user. I think there is some risk to that compared to just grinding it flat though; you can bend it too much too.

I was also under the impression that flattening the entire back is a good practice, so the whole surface is in plane with the sharp edge; a good feature to have if you are paring deep. Note, I'm not talking about honing and polishing the whole back, just flattening it.
 
#13 ·
Homick, I've bent a plane blade and a chisel carefully using the three dowels in the bench vise trick that I learned here on LJ maybe from DonW. Two dowels on one side, one on the other at the high spot and slowly close the vise just enough past where you want it to end up. If you are careful enough you can bend it just right.
 
#14 ·
The only reason to flatten the entire back is to make it pretty. I only worry about the bottom inch. Polishing the entire back will not make it any sharper. I would concentrate on the bottom inch on the back and the bevel on the front.

- Redoak49
I agree with this approach, with two possible exceptions: for doing very fine paring work, and in the case of a mortising chisel, where having a perfectly flat back helps the eye determine true vertical when chopping the ends of a mortise. But for ordinary chiseling around, what you have now will be fine.
 
#15 ·
I don't know where and when the trend of flattening the entire back started but I can tell everyone here, with 17 years under my belt as a shipwright, it's complete bullocks. I will even say that anyone who needs a completely flat chisel isn't much of a woodworker. Only the first and last 2-2.5cm of the blade needs to be flat. That goes for everything from fine paring work to chopping a mortise. It's even less important for a plane blade. Stop listening to all the self professed woodworking guru's such as Schwarz and Cosman and learn how to use a chisel.
 
#16 ·
You found the problem. I will add:

1. I agree you only need to flatten the first couple inches.

2. make sure your stones are flat & reflatten every so often during the process. And be sure whatever you're flattening with is flat!! I bought a Norton flattening stone only to discover IT WASN'T FLAT!!

3. Like Bondo, I keep dropping grits until I get it flat - all the way to 100 grit if needed.
 
#17 ·
I use DMT diamond plates.
course grit to get it started - extra fine to finish
strop (leather glued to wood block) with green compound to polish the edge sharp (if you cannot split a hair with it, it is not sharp.

I have found that anything more than an 3/4" on the back doesn't do you any good - except keeping the angle of the back in line with the handle. If there is a twist to the blade, take it back if new. If it is pre-1955 or so and has a twist, flatten the back - once. This will be made with tool steel and will take a few hours. If it only takes a few minutes to flatten and sharpen, it will dull faster than it takes to sharpen it.

If it is a Japan style chisel, only the edges (sides and cutting edge) matter, the center is hollow ground.
 
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