Flattening back of a mishandled chisel

[Gary Herrmann]

I use a belt sander with 80 grit on it for this kind of thing. Get's the bumps out fast. I wrote metal inside the belt so I wouldn't use it on anything else.

[Mark ten Haaf]

Thanks. That makes sense. No reason to work more than necessary. :-)

(....he said on the neanderthal forum....)

I'm just saying.......

[Tony Shea]

IMO, lots of these older chisels we come across were manufactured with an ever so slight belly. Not sure what the exact reason is but may have something to do with getting a bit more handle clearance in certain situations. Maybe some are caused by improper honing of the back but it really seems odd to me that same brand chisels found at different locations have identical bends to their backs. It shouldn't be a huge belly but like has been stated it really is only the first inch or a bit more that needs to be flat.

Im by no means 100% sure they were designed this way but have come across enough of them that instills this theory.

[Jim McFarland]

I have a couple of Japanese paring chisels with significant bellies (1/32" on 1 & 1/16" on the 2nd). Being accustomed to Western (LN) chisels with reasonably flat backs, I asked the reputable vendor if this was common or a defect. The response was this is common for these chisels and the curve provided "steering control." Vendor could have been blowing me off but...just in case they weren't...think of all the "steering control" you have with your chisels and just flatten the tip! I don't really know what steering control means but the chisels work well enough and I quit worrying about the belly.

[John Coloccia]

If the belly belongs there, why do they hollow grind the backs of the chisels? As I understand it, the only reason for doing that is to allow you to flatten and maintain the chisel in a reasonable amount of time given metal used for the back of the blade. If they wanted it curved, wouldn't it be simpler to not have a hollow ground there? I'm no Japanese chisel expert to be sure, but the explanation seems a little fishy. Maybe I'm missing something.

Anyhow, the most frustrating thing in the world to me is trying to pare with a chisel that isn't flat. I go over the same spot 15 times and miss. Then I lift the back just a tinny bit and miss again. Then I lift a little more and it digs in and takes off too much. When the back's flat, paring seems much simpler to me.

[Jessica Pierce-LaRose]

I had a wide chisel I bought at a junk shop, that had a bit of belly on the back - it was taking a bit too long to lap the back, so I went with a tip I think I read in Garrett Hack's book; I used a small grinding wheel, the kind you chuck in a drill. I used that to grind away a bit from the middle, keeping away from the cutting edge. Then lap a bit more, to see how things are looking, and grind a bit more. Back and forth for a while; I ended up with a very, very slight hollow grind that has since mostly disappeared after lapping the back briefly after sharpenings. I did this a long time ago; I have no idea if this is a good idea or not, and I've only done it a couple of times, when I had a situation where lapping was taking an obscene amount of time, even with course paper. But just thought I'd mention it.

[Pam Niedermayer]

...Anyhow, the most frustrating thing in the world to me is trying to pare with a chisel that isn't flat. I go over the same spot 15 times and miss. Then I lift the back just a tinny bit and miss again. Then I lift a little more and it digs in and takes off too much. When the back's flat, paring seems much simpler to me.

You might want to try a bevel down approach.

Pam

[Staffan Hamala]

The work is going slowly forward. The back is getting flatter, but I still have the two dips in the corners which I need to remove.

Just to get a bit of a change, I left the 3/4" chisel be for a while, and gave the same treatment to a 1/2" chisel. Which this one I concentrated on the first inch right from the beginning, and not more than an hour later, I had gone through 80, 180, 240 grit sandpaper and 800,1200 and 6000 grit water stones, and am really delighted with the result. I'll finish the 3/4 inch chisel in the next few days as well.

I tried to get a photo of the mirror polish of the 1/2" chisel but it's really difficult to get it to show on a photo.

I'm attaching a couple of photos anyhow. The finished chisel, the half finished one, and one photo of the both of them. Very interesting to note that one is so much shorter. I guess it was my grandfather's favorite! :-)

[Staffan Hamala]

I finally gave up on trying to fix the corners, so I concentrated on getting the rest of the first inch flat.

IMG_3448b.JPG

I managed to get a good edge however. But I'm a bit annoyed that I didn't manage to fix the corners. I might give it another go later on, or I might just grind away the first 2-3 mm of the chisel. For now, I'll use it as it is.

[Harlan Barnhart]

Joshua, I tried something similar but I used a regular grinder instead. I held the chisel to side of the wheel at a VERY low angle and CAREFULLY ground a hollow in the back. You want to practice with a junker first. I probably would not practice with an old swedish Berg from my grandfather...