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View wilbrijo06's profile

Chisel Flattening

by wilbrijo06
posted 11-20-2016 09:25 PM

16 replies so far

View paratrooper34's profile


915 posts in 4033 days

#1 posted 11-20-2016 09:34 PM

BW – you are polishing way too much of the back on that. You need only polish about an inch or so (max). Try polishing to that and you should have much better luck. As it is, you are trying to polish a lot of metal.

-- Mike

View wilbrijo06's profile


8 posts in 2820 days

#2 posted 11-20-2016 09:41 PM

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.


View Tim's profile


3859 posts in 3042 days

#3 posted 11-20-2016 09:53 PM

What Mike said and yes, go way down on your grit until you get it flat, then move up through the grits. Careful, sandpaper can round the edges. Personally though, I would take back a chisel that was that far out of flat.

View WhoMe's profile


1568 posts in 4324 days

#4 posted 11-20-2016 10:04 PM

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.

-- I'm not clumsy.. It's just the floor hates me, the tables and chairs are bullies, the wall gets in the way AAANNNDDD table saws BITE my fingers!!!.. - Mike -

View wilbrijo06's profile


8 posts in 2820 days

#5 posted 11-20-2016 10:07 PM


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…


View bondogaposis's profile


5986 posts in 3432 days

#6 posted 11-20-2016 10:07 PM

Use a coarser grit, you should be able to flatten it in 5 minutes or less. If it takes longer than that keep dropping grits until you get it. I use a coarse diamond stone for flattening.

-- Bondo Gaposis

View GregTP's profile


63 posts in 2024 days

#7 posted 11-20-2016 11:09 PM

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!

-- From exercise machine warning label: "Step ladders can cause injury and even death; the ROM machine is more dangerous than a stepladder"

View mike02130's profile


170 posts in 1753 days

#8 posted 11-20-2016 11:23 PM

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.

-- Google first, search forums second, ask questions later.

View Redoak49's profile


5242 posts in 3069 days

#9 posted 11-21-2016 01:55 AM

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.

View Homick's profile


23 posts in 3002 days

#10 posted 11-23-2016 03:07 PM

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.

View HokieKen's profile


17542 posts in 2219 days

#11 posted 11-23-2016 06:49 PM

FWIW, I did flatten the backs all the way on my paring chisels. All others just get the inch or so at the cutting end though.

-- I collect hobbies. There is no sense in limiting yourself (Don W) - - - - - - - - Kenny in SW VA

View Tim's profile


3859 posts in 3042 days

#12 posted 11-23-2016 11:37 PM

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.

View ClutteredShop's profile


38 posts in 1633 days

#13 posted 11-24-2016 04:57 AM

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.

-- Cluttered Shop

View Lemwise's profile


91 posts in 1698 days

#14 posted 11-27-2016 10:08 PM

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.

View Robert's profile


4556 posts in 2562 days

#15 posted 11-28-2016 03:17 PM

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.

-- Everything is a prototype thats why its one of a kind!!

View dbray45's profile


3408 posts in 3857 days

#16 posted 11-28-2016 03:52 PM

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.

-- David in Palm Bay, FL

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