Ura-Dashi Musings

[Brian Holcombe]

Hope you guys are well, been working away but most of my work as of late are repeats of my recent builds. That is good for me, but a bit boring for the blog, so I wrote up some details of how I've improved upon my ura-dashi in recent months.

This is an off-shoot of a post I did a while back called Ura-Dashi: Failure and Success, detailing my improvements and newly formed goal.


https://brianholcombewoodworker.com/...dashi-ito-ura/

[ken hatch]

Brian,

I just finished reading you post, as always good info.

Thanks
ken

[William Fretwell]

I've watched some Japanese videos doing this, all in Japanese of course. The best was a Japanese University video studying chip breaker position and presentation angle for different depths of cut as it relates to tear out especially against the grain.
That video is essential viewing for Japanese planes and totally applicable to Western planes as well. I did not store the link but should be searchable.

[John Stevens]

Thank you very much, Brian. I had tried to do that with my chisels after reading Toshio Odate's book, but your photo essay gives me a lot more info.

--John

[John C Cox]

I really wish these techniques were applicable to western chisels and plane irons. A very slight dish on the bottom of a chisel or plane iron makes the very hard high quality steel just so much easier to sharpen... Add to that the thin sliver of hard laminated to the bottom of the soft... And I think this adds up to why western planes and chisels tend to be made of much lower carbon steel tempered much softer....

"Good" conventional steel western chisels run between 0.75% and 1.2% C.. Japanese chisels run 1.2-1.4% C on the cutting edge. Its just too hard to sharpen conventional western chisels when you run the hardness and carbon content way up there to where the Japanese run them...

[Brian Holcombe]

Thanks fellas, I appreciate the comments!

[Stanley Covington]

Allow me to point out a small detail about what Brian has done.

Note that the chisels he worked on are not conventional ones made to be hit with a hammer, but are closer to carving chisels in construction. You can see the difference in the photo where the line of high-carbon steel goes straight across the bevel and does not wrap up the sides of the blade. As Brian noted, they are made by Konobu, a blacksmith located about 20 minutes from where I live and who specializes in carving chisels. With few exceptions, he does not make standard chisels with HC wrapped up the blade's sides. Wrapped steel construction adds considerable strength to the blade, strength and rigidity absolutely necessary in the case of chisels intended to be struck with a hammer.

My point is that chisels of any width like the ones Brian showed respond well to uradashi. However, standard chisels with wrapped hagane will not deflect properly at the sides of the blade due to the extra strength the wrapped hagane affords. Therefore, and especially in the case of standard chisels with wide blades, uradashi can be made to work at the center of the cutting edge, but not the sides. By extension, trying uradashi on narrow blades can actually break them.

My advice is to make sure you are good at doing plane blades before you try uradashi on standard chisels.

Stan

[Phil Mueller]

Brian, while I'm pretty sure Ura-Dashi isn't something I'll ever tackle, your posts are welcome information on a very interesting technique. Appreciate the time you took to put this together. And thanks also Stanley, for your added insight.

[Brian Holcombe]

Stan, thanks for commenting! I think I will add to my comments on the chisels on the blog so that people do not start doing ura-dashi on their chisels.

BTW you've probably seen this already but Konobu recently started making plane blades, I picked one up (42mm). Excited to try out his work in this context.

My pleasure Phil!