Fixing a Chipped Japanese Chisel Blade

[Woodbloke]

Not so much a sharpening thread as a 'fixing' one. Last week when chopping out the rear panel rebate corners, my 12mm Japanese chisel stopped behaving as a proper chisel and started cut weirdly. When I took it out of the cut, it soon became evident as to the reason:



Being a 'silly billy' I'd forgotten that I needed to treat these things with a bit more decorum and civility than my Western 'Richter' ones. A Japanese chisel takes an incredible edge but it's so easy to chip it with the slightest lack of due care and attention. I decided this morning then, to do a 'fix', so stuffed it into the Veritas MkII Honing Guide with the chisel attachment:



.... to hone a single bevel at 30deg on a 1000g water stone.

Half an hour later I was still at it with little sign of the chip retreating. Having purchased an Ax 'Ultimate Edge' I wondered if the Japanese chisel would fit into the plane/chisel jig, but surprisingly it did:



With a new 120g belt installed it was only a couple of light passes (with some cold water dunking inc) to remove the last of the chip. I thought I might have to do some work with the 'Kanaban' lapping plate and some coarse valve grinding paste (!!) to shift the 'ura' (the depression in the back) down a smidge but didn't really need to:



...as there was still about a mm between the edge and ura.

Then onto the waterstones and strop to remove the grinding marks and finish the single bevel at 30deg:





Japanese chisels can quite easily be 'fixed' (with care!) but I'd suggest that attempting the repair freehand is fraught with difficulty. Apologies also if the sight of waterstones and sharpening gear make you splutter on your coffee and cause the dunker to break off and disappear to the bottom of your mug - Rob

 

[Cabinetman]

Never had the need for a jap chisel but often wondered what happens when you sharpen back to the ura, do you have to reduce the thickness of the chisel to bottom depth of the ura?

 

[BentonTool]

BTDT...

 

[Dr.Al]

Never had the need for a jap chisel but often wondered what happens when you sharpen back to the ura, do you have to reduce the thickness of the chisel to bottom depth of the ura?

I remember reading somewhere that the laminated construction means that you can (carefully) hit near the tip with a hammer & the softer backing metal will bend slightly and expose more of hardened cutting edge, so there's not as much work needed to flatten it (i.e. you don't have to flatten the entire back of the chisel again).

However that might just be plane blades or it might be me misremembering or misunderstanding: I've never really explored Japanese laminated blades.

I'm sure someone will be along shortly to explain why what I've written there is nonsense!

 

[Woodbloke]

Never had the need for a jap chisel but often wondered what happens when you sharpen back to the ura, do you have to reduce the thickness of the chisel to bottom depth of the ura?

Nope, you just need to pass the back over a coarse/fine stone of some sort to 'shrink' it a bit; doesn't need to be very much, just enough to give some clearance between the depression and the edge. They're very good indeed when set up correctly (that takes some time!) but can be an 'acquired taste'...but they're capable of a sublime cutting edge - Rob

I remember reading somewhere that the laminated construction means that you can (carefully) hit near the tip with a hammer & the softer backing metal will bend slightly and expose more of hardened cutting edge, so there's not as much work needed to flatten it (i.e. you don't have to flatten the entire back of the chisel again).

However that might just be plane blades or it might be me misremembering or misunderstanding: I've never really explored Japanese laminated blades.

I'm sure someone will be along shortly to explain why what I've written there is nonsense!

You can do it that way Dr.Al, but I think you really have to know what you're doing; not something I've ever attempted - Rob