Strategy For Chisel Backs

[Jack Straus]

Hi all, first post here. Hoping someone out there has an idea for working these chisel backs. I found this set on ebay about a week ago. I have been casually looking for a 10 piece set with the kaku-uchi shape, so when these revealed themselves for a couple hundred bucks, I figured I did not have much to lose and clicked buy.

They arrived this morning (fast shipping!) and here is how they look with the lacquer off and a quick pass on the lapping plate to see what kind of shape the bevels were in ( I think "convex" would be the the appropriate descriptor).

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And here is a shot of the stamp. Some of the handles still had their sticker, which read "Narumiya Sato"

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So far so good. The superficial rust, stains on the handles, and rounded bevels were all to be expected on this cheap used set. I went to work lapping the backs so that I could get these bad boys sharpened up.

As I draw the first chisel across the stone I feel a disturbing rocking and feel a corner dig in (keep in mind the ura looks brand new). I get confused and see if there is a chunk of dirt or something on the stone that is causing the chisel to rock. No dice, stone looks clean, and back of the chisel looks like it just came from the smith's shop. So I reference the back of the chisel on my DMT plate (flattest thing I own) and the chisel is rocking back and forth like crazy. There is a clear "high axis" from the back left to the front right corner. Below are two pictures with me pressing on the respective "low spots" with a .020 feeler gauge underneath the resulting gap.

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I think maybe this a just a bad apple, start checking the others it the set -- and they almost all have the same issue with the exception of a few of the smaller sizes.
So where to go from here? Should I rub these against a lapping plate for the rest of my life? I am sure I could eventually get them flat, it would take some time and create a very asymmetrical wear pattern on the ura.

Should I just focus on creating a flat behind the cutting edge? I would be able to get the chisels sharp, but couldn't use the chisel back as a reference when paring.

Can I beat these with a hammer a little bit to try in move the back into a single flat plane? Like an aggressive version of tapping out?

Any suggestions appreciated.

- Jack

[djwong]

Hi Jack,
You ask a great question for your first post. Unfortunately, I do not have a good answer for you. I have a set of Kunikei chu-tataki chisels, and many of them have convex backs. I decided to only flatten the front area of the chisels to avoid lapping away too much metal, and to not mis-shape the ura too badly. Of course this means I cannot register the full bottom of the chisel to guide a cut. I did consider beating the chisel (with a block of wood or soft metal ), but I did not want to try this on my new chisels.

I previously posted about this here.

[Matt J]

No good answers here, either. I'd probably just flatten the fronts. But if you do decide to give them a whompin', you might warm them up a bit first- not hot enough to affect the temper, but just enough so they're a little relaxed, not cold and brittle. I'd try leaving one blade down in a cup of very hot (or maybe even boiling) water for a minute or two, then whomp with a wood block, or squeeze in a vise, etc. Definitely don't hit the ura side directly with a hammer. Actually I wouldn't hit either side directly with a hammer, unless tapping out.

[Brian]

This is a tough one, .020" is a ton IMO. I'd like start by working with a large wooden drift pin then finish the job via tapping out. Tapping out aggressively on chisel with ears, as most have) stands to weaken it from what I've been told. I tend to tap out very minimally on chisels with mimi and more freely on chisels without or plane blades.

A good ura can be achieved in all likelyhood but how you manage the work before going to the stones will likely determine.

Konobu, as an example, never seem to contact at the front edge without some work. The first few I treated as normal chisels just working the backs with rough stones...,it took hours and the backs were ok but not as sexy as when I received them. The remainder I tapped out to wonderful effect and took maybe 5-10 minutes to setup the backs.

[djwong]

Think the chisel reads 菊之助 - kikunosuke. Either the brand or someone's name.

[Brian]

Konobu had a sori situation, the left side were tapped out and finished on 10k then natural stone , the right side worked from 1k through natural

https://brianholcombewoodworkerblog.fil ... g_7477.jpg

[Jack Straus]

Thanks for the ideas. I ended up taking the chisel to the anvil -- promptly broke a massive part off of the corner, got into the fetal position and let the despair sink in. When I regained consciousness, I ended up grinding about 3/8" off the tip, ground a new bevel, and did more tapping out than I would wish upon anybody. Now I have a much shorter chisel, with a flat back and a decent looking ura, so success? I have a penchant for learning things the hard way. I will try a different approach with the other 9 chisels in the set.

[djwong]

Jack,
Sorry to hear that. I know it does not help, but we all have done something like that. Here is mine.



Can you say how you attempted to flatten the chisel on the anvil? Did you have the hard steel or soft iron on the anvil? Did you strike a wood block on top of the chisel with the hammer? I still would want to try this someday, but probably on an old chisel first.

[Brian]

In the same camp, and rather unexpectedly since it was going quite smoothly until it didn't. It prompted me to re-evaluate my process however and now I can tap mostly with confidence (unexpected things can happen).

This blade, likely for reasons like having a poor lamination at some spot in the weld, made a massive crack after some tapping out. I never hit the hard steel, and in fact the crack formed (I heard the ping) while I was holding the blade and walking over to the stone, rather than while actually tapping.

https://brianholcombewoodworkerblog.fil ... g_5319.jpg
https://brianholcombewoodworkerblog.fil ... g_5320.jpg
https://brianholcombewoodworkerblog.fil ... g_5321.jpg

I thought to trash it, but I ground past the crack and fixed the blade:

https://brianholcombewoodworkerblog.fil ... g_5626.jpg

I'm glad I did because this blade sings! Really an awesome piece of steel and iron.

[Chris Pyle]

my suggestion: sell them on ebay and try to recoup your money and replace them with something like this: http://www.ebay.com/itm/Set-of-ten-Japa ... SwHjNWBmaA I've seen sets go in the upper $200s but usually average around mid 300s

I'd be shocked if those Kikuhiromarus had anywhere near that amount of distortion. I'm all for learning on cheap tools but the remaining 9 chisels may end your affair with J chisels and that would be a shame.

But if you don't want to sell or that's more than you'd like to spend, I hope the chisels serve you well (after you pour yourself into them).

I've come around to the idea there are very few "deals" when it comes to Japanese tools. American culture is driven by the "deal" mentality but I think it's far safer to assume 'you get what you pay for'. Certainly people can find a good blade or a good chisel on an auction site but I know how I'll spend my money with any future purchases.

If you do continue setting them up, let us know how it goes.