# How do you re-flatten a hollow ground chisel?



## Lola Ranch (Mar 22, 2010)

All,

I have a set of Japanese chisels I've had for many years. The back side of each chisel has a hollow ground depression and what used to be a flat area about 1/4" ending at the leading edge. Some of the chisels have been sharpened enough times that the cutting edge has reached the hollow. 

I've never had to re-flatten them before. I think you are supposed to tap the edge with a ball peen hammer on an anvil. Then of course you would have to lap the back side again and grind a new bevel because I am assuming you will have a crooked edge after the back was re-flattened.

I'd like to hear from an expert on this matter before I jump into it. I love these chisels and I don't want to damage them.

Thanks, Bret


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## sawdustfactory (Jan 30, 2011)

Bret, I remember seeing something about this, I just can't remember where. You might want to check JapanWoodworker, it may have been on their website.

Memory isn't failing me after all. Here's the link. http://japanwoodworker.com/page.asp?content_id=2744


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## Lola Ranch (Mar 22, 2010)

Thanks for the link. I'm glad I asked. The method is much different than i thought.

Bret


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## firemedic (Dec 26, 2010)

Lola Ranch said:


> I've never had to re-flatten them before. I think you are supposed to tap the edge with a ball peen hammer on an anvil. Then of course you would have to lap the back side again and grind a new bevel because I am assuming you will have a crooked edge after the back was re-flattened.


I'm really intrigued by this. A peen hammer?


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## woodnthings (Jan 24, 2009)

*I was interested also*

So I copied the text from the link: 
http://japanwoodworker.com/page.asp?content_id=2744

"A new chisel should always be honed prior to use. First, the back of the chisel must be honed on a flat coarse stone (#1200 or #2000 grit stone preferred) until the area directly behind the cutting edge is completely flat across the width of the chisel. To do this, rub the back of the chisel side ways along the length of the stone. The proper technique is to keep the chisel flat on the stone with finger pressure applied directly on the bevel. Keep rubbing until the area directly behind the cutting edge is flat. This will be obvious by inspection. Second, transfer the chisel to a flat #6000 Finishing stone or #8000 Polishing stone and hone as above until a mirror surface is obtained.  Future sharpening will require that the chisel back be honed only on the Finish or Polish stone *unless after repeated sharpening the cutting edge reaches the hollow grind. *If this happens, it is easily corrected by following the above procedure until about 1/32" of flat area is re-established.  
After the back has been honed and polished, the bevel of the chisel is sharpened. This is done by rubbing the bevel on a flat coarse stone until the "burr" is turned up. At this point, transfer the chisel to the finish stone and alternately hone the bevel and back of the chisel until a razor edge is obtained." 


What I don't get is, when the hollow back extended to the cutting edge, how you get back to a straight area ...*without reducing the thickness of the tip*? Maybe that's just the way it is. :blink:​


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## firemedic (Dec 26, 2010)

Bill, the hollow on the back is very very shallow. It takes very little lapping on the back to reestablish a flat at at the edge. 

It's thinning the chisel, yes but minutely. No different than when you hone the back of a regular chisel. It's usually doesn't come up if you regularly lap the back as part of your sharpening routine. 

The point of the hollow on the back is to allow for quick and accurate flattening.

I was asking about the peen hammer because Brett knows his tools and I'm stumped as to what he's talking about :huh:


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## Lola Ranch (Mar 22, 2010)

Gotter done. It took about 10 minutes of lapping on a fine ceramic stone. It could have taken less time if I'd started with a medium grit.

Bret


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