Tuesday, March 25, 2014

Get (un)bent!-Straightening a bent chisel

OK, a good chisel, but one with issues. How far dare I go? The chisel is bent to the front, just a bit, but enough to be bothersome. This could be SO nice otherwise......

The bend.

I warm the chisel with a heat gun, thinking to reduce the shock of bending, somewhat. I am using my big 'ol machinist's vise with 3 movable fulcrums. Two are made out of oak, the third is a brass rod.

 The oak pieces are hook shape and have a small magnet glued into the back, where it contacts the jaw of the vise. The magnet attachment allows you to slide things around, to apply force right where you need it.

I periodically check for flatness by grinding the back of the chisel, using a diamond grit bench stone. There was a fair amount of rust pitting to eliminate, but the hard steel is thick enough that I didn't have to worry TOO much about grinding through, into the soft iron.


Not perfect, but at least something that I can live with.

The diamond stone that I am using isn't truly flat. For that I need to use a different technique.

Lapping the back, using valve grinding paste on a granite plate/tile.

The black stick looking thing is....a stick. I use it to apply more pressure, directly over the cutting edge. My right hand wraps around both the handle of the chisel AND the stick, supporting the weight, my left hand applies the  downward pressure. 

The paste is VERY thick, so I thin it a bit with some mineral oil. Keep the paper towels handy, this is really messy! Ahhhhh.....memories of sandpaper and oil, scary sharp (yuck!).

You can see the rough/grinder spot that I mentioned, the black area on the right. If I try to take the whole back down to that level, I'll lose the ura completely and the hard steel would be getting alarmingly thin. It might become an issue in 10 years or so, but for right now, this is fine.

The lamination line looks very nice. 

Unfortunately, the side of the blade had some significant corrosion issues. I had to grind down the worst of it, leaving the lamination line a touch asymmetrical. Aesthetics aside, this will be a very useful chisel.

The finished chisel. The boxwood handle has been trimmed to shape and French polished. 

I made a new sharpening stone the other day, using some demo waste from our neighbors rock wall. Probably my best local found stone yet. It is hard, a little sticky, and makes a small amount of slurry on its own, but likes a diamond nagura if you are in a hurry. It starts at about JIS#4000 and seems to work up to around #6000. 

There are still a few butt cracks (sorry..), but for the most part, the handle cleaned up nicely.

A slight asymmetry, damned rust!

For sharpening this chisel, I used a nagura, a pink Akapin "Nakayama" that I bought from eBay seller japanathome (could this be another 330 mate name, hmmm?). They are sold as "maruka" Nakayama (highest quality from a particular old supplier), but these don't look ANYTHING like maruka's from reputable sellers. 

That said, the stone does work nicely as a  (big) nagura and for the $25 I paid (delivered!), I like it well enough. I wouldn't pay $50, though....

Even with all of that grinding of the back, the ura is still nicely shaped, go figure. Nice chisel, good thing that it didn't break in two. 

Lucky me.


  1. Awesome blog! I don't usually find too many blogs with Japanese tools, something I'm getting into, so thanks for sharing. I also shared it on my woodworking blog feed, so hopefully you'll get a few more like minded readers, http://woodspotting.com/news/3339

    1. Thanks for your comment Siavosh. The Japanese tool thing has a certain learning curve associated with it, but therein lies the fun! Thanks for visiting.


Like all of us, I am figuring this out as I go, so when you see something that is incorrect or flat out wrong (and you will!), let me know. This is a learning process. Real people and names, please. Constructive comments and questions are very welcome, but hate speak/politics are not! Life (get one!) is too short.

Thanks, Jason