plane blades, non western

[Ron Petley]

Not to hijack Dereks post I have started a new one.
Dered posted this site which has some intersting items in it to say the least:
http://japantool-iida.com/plane_smoothing/2009/02/ichi-seisu-by-yokoyama.html

Onec I got past the price of these things, the detail of them is impressive, all hand made, hence the price, free to look though.
How the chip breaker and blade have a "scooped" grind to them has caught my eye. It is on both the cap iron and blade. The "western" thinking has run along the lines of a flat back of the plane iron, to seat tight on the "ramp" of the plane, not so in this case.
Also the extent of the scoop runs very close to the iron edge, so only the very edge will contact the plane body.
This also might limit the sharpening millage from the blade before it would need some serious re working, this part is spec on my part. At that price I would be wanting this thing to go to the kids when I am dust.

Cheers Ron.

[Sam Takeuchi]

When the hollow gets close to the edge, simply do uradashi to create flat area immediately behind the edge and flatten to level the newly created flat area with the rest of un-scooped area. It'll definitely last beyond your life time.

Check out this page (http://www.tsune36.co.jp/repair.html). Scroll down to the middle of the page, it shows a plane iron, perfectly used to the very end without destroying the hollow. That's a plane iron used by a professional carpenter and took 30 years to get that much. That's one of the most perfectly and skillfully maintained piece of blades. I think for a mere woodworker, it'd take a few generations to finish it off like that.

[David Keller NC]

Ron - You may have something a bit confused. Japanese planes, like their western counterparts, are generally bevel-down tools, not bevel up. So the hollow in the back of the balde actually faces up in the plane stock, not down. The "front" of the blade has no hollow, and beds into the plane body just they way you would expect on a western wooden plane.

The hollow is there, by the way, not for chip clearance or other consideration with respect to its use in a plane body, but as a sharpening aid. Because these blades are laminated, with a very hard white or blue steel that forms the cutting edge laminated to a soft wrought-iron blade blank, it would take days to flatten the back of the blade as one does with a western plane blade. For this reason, the back is ground hollow so that only the very tip of the iron need be flattened. Once the edge approachs the hollow, the plane blade is bent by hammer taps or the use of a tapping tool to re-establish the flat, then the blade is put back on the stone and this area flattened to restore the blade to its original, albeit shorter, configuration.

As you might have surmised, in Japan it is all about the blade, not the carrier (the plane body). Most of these that are carried in high regard are made one at a time by a very skilled blacksmith artisan. Some of these blades by famous blacksmiths can cost over a thousand dollars.

[Ron Petley]

Thank you David, yes bevel down now makes sense once you say it.
Also the part I was missing was tapping the blade edge flat before reworking it.
Thanks for clearing it up, it all makes sense now. also it is eaasy to get a sense of respect for the iron maker, as it should be for such a highly refined metal working skills.
Cheers Ron.

[David Keller NC]

Ron - If you're interested in this subject, consider buying a copy of Toshio Odate's "Japanese Woodworking Tools". It's inexpensive, and is the bible on these types of subjects. He's got a good 20 pages discussing japanese plane blades - the types, how they're produced, and how they're maintained.

[Ron Petley]

Thank you David.
Ron.