Tuesday, December 21, 2010

Ramping Up for New Action

In order to have a shot at working the curly bubinga for the current Ming-inspired table project, I anticipated I would be doing a lot of scraping. With a card scraper, and the acreage of wood needing surfacing, my thumbs were facing a nightmarish scenario. While it wasn't keeping me up at night, or giving me thoughts of skipping town, I was looking into alternatives. So, taking another tack, I was thinking of obtaining a scraping plane, say one made by Lie Neilsen or Lee Valley, but before going that route I decided it would be worthwhile making a plane dai to bed one of my existing plane blades at a steeper angle. If that did the trick, then I wouldn't need to bother with the scraping plane.

Now, I'm not entirely sure exactly what the magic number, in terms of angle, I need to set the plane blade at so as to have no tear out with curly bubinga. To be on the safe side, given that I would be chopping into a carefully hoarded 30-year seasoned piece of Japanese white oak, shirogashi, for the plane's block, I decided to place the blade at a 60˚ angle. I figured that would likely work - if i could pull the 70 mm plane in such a set up.

Now as all those math-heads and battle-scarred SAT veterans know, a 60˚ angle, which is part of a 30-60-90 right-angled triangle, is formed by a right angle with a rise of 1, a hypotenuse of 2, and a run of √3. In a post (<-- a link) way, way back in time, I described how that special 30-60-90 right triangle is found using the compass and the vesica piscis. In this case, cutting to the chase, I used some trig, taking the tangent of a 30˚ angle, and then measuring out a large right triangle using that obtained measure and so produced a 60˚ angle. Then I set my bevel gauge to that angle:

And, with the aid of a try square, transferred the 60˚ line to my precious piece of white oak:

Now, I took way too many photographs today. Over-indulged, you might say, so in the interest of keeping the post to less than 30 photographs, I have to cut out the odd step. Sorry about that.

Once the lines for the plane blade were laid out on the dai, I took it over to the hollow chisel mortiser and made a start on the excavation:

Then, out comes a bench chisel:

A few minutes later, I was digging that proverbial hole to China:

As I got closer to the bottom of the block, I flipped it over and made some preliminary chops on the mouth opening:

A while later, after some vicious kickboxing, I had punched a hole through the mouth:

A view from the other side:

Then I started tidying up the mouth a little bit, using a paring block set at the angle I wanted, which was 80˚:

Then I returned my attention to the top of the dai, and began paring the sidewalls, using a gauging block and, well, would ya lookit that! - the jointer table comes in handy!:

With the side walls of the opening in plane with the sides of the dai -- oh, did I mention that this all began with a dai that was straight and square? -- little details, I know, but an important one, with the side walls ready, I laid out the lines for the side trenches which hold the blade and got out the detail saw:

These little ramps are quite critical parts of the set up and its important to be fussy and get them right.

Once the saw cuts were made, two for each ramp, out comes a skinny paring chisel:

Here's the resulting rough-cut dai:

So all the above hacking and stumbling went fairly quickly, maybe an hour. The next part took quite a while longer - fitting the blade to the mouth.

Attempt 1:

Now, to gauge the fit, what you have to do is find a way to transfer marks from the spots that the blade rubs on. I've tried using pencil/graphite, and I've tried using camelia oil. What I find works the most effectively, however, is neither of those: it is both of them combined together. I rub the blade with a carpentry pencil, then put a few drops of camelia oil on and rub it around, then fit the blade. It works like a charm. At the first attempt, the blade barely fits and there was but one small area of contact:

And then the process is repeated, and repeated, and...well, here's the scene a few steps further along:

Now you can see that the blade is now at least on speaking terms with the dai:

A while later, and they're starting to get real friendly, like:

You could say this is the beginning of a beautiful friendship, though things are definitely touch and go:

Now, in the early stages of fitting the blade, I use a chisel to slice the points of contact down. That allows the blade to move down in a reasonable amount of time. but as one gets closer and closer to the final fit, just like with joinery work, it is the time to slow down and do a little less with each round of material removal. some people like to use a file, or a file with a burr rolled on one end, however I like to use a bottom-scraping chisel or soko-zarai nomi, to make those fine adjustments in the final hour or so of fitting:

You can tell you're getting closer, not only by how far down the blade goes, but by how completely the surface is blackened by the blade rubbing on the wood:

A while (or was it a lifetime?) later I had the blade within a millimeter of peeping out:

This is the view at that point inside the mouth:

If the blade were driven down much further, it would run into the escapement, and if I wasn't paying attention might split the wood out. Not a great thing to have happen. I made a second paring pass on that 80˚escapement using the paring block, just to make a little room. I want the mouth to be fairly tight, but I'm not obsessive about that. The tightness of the mouth opening plays a role in getting good results, but I haven't found it to be extremely critical.

Once I made a few more tweaks, the blade was down. What I aim for is a fit where the blade fits snugly all the way around the lower end of the back of the blade, just before the blade bevel begins. You can see the dark even mark formed by that area of the blade in this picture:

Okay, well there it is, a 60˚ version of a 70 mm Funahiro Tenkei:

The working surface, prior to tuning:

As for how/if it works, well, stay tuned for a follow-up post.

Thanks for taking the time out to check in on things here, and I hope to see you again soon. --> go to post 2


  1. Beautiful work Chris. Have you studied with Inomoto-san or did you learn on your own? I'm looking forward to seeing your post on how it performs.

  2. Thanks Dale.

    I learned on my own, picking up what I could wherever I could find it. Still learning!


  3. Chris - this is possibly the best write up on making a dai I have seen. Not having to obsess about he mouth opening gives me encouragement to have a try at this myself.

    One thing I don't understand is the use of Japanese white oak. Is this just a matter of tradition or does Japanese white oak have some unique properties necessary for dais? If not, what else can one make dais with?


  4. Anonymous, I will allow your comment this time though you do not append your name. I make the exception only because your question was something I thought would be of interest to others. While I'm not a total rule freak, I've had problems in the past with anonymous commenters so am somewhat of a stickler on this matter.

    To you question: Japanese white oak is possibly the most perfect material for a dai, due to it's density and 'just right' amount of elasticity. It's a very stable wood, is easy to sight along because it is light in color and wears well. My favorite wood for a dai.

    You can make dai out of a wide variety of woods. You need something stable and not overly brittle, tough enough to wear well, and not too hard to chop out. Lignum vitae would be a tough wood to make a block out of. Purpleheart would be about as hard as might be ideal. I've made dai before from American Red Oak, which is not what I might recommend, but it worked out just fine. Live Oak, if you could find some stable material, would be a good choice, as would Hop Hornbeam. Even beech. There are many possibilities.


  5. Hi Chris, just wishing you and your family a great time over xmas. And thanks so much for all your efforts during the year to keep everyone informed to what i think is the best blog on Japanese woodwork. The totally thorough approach to your work both theoretically, and practically is a constant source of informed knowledge.

    On a more basic note can you tell me the brand of Nomi you tend to use.
    And if you have any information on where i can buy a Japanese Dovetail plane i would be very appreciative.
    I really like tapered sliding dovetails but can't seem to find a dovetail plane anywhere apart from the ECE brand.


  6. Hi Chris

    This is for sinjin: http://japantool-iida.com/plane_others/2009/05/dovetail-plane-by-tasai-and-ki.html

    Hida has one listed as well: http://www.hidatool.com/shop/shop.html

  7. Hi Chris,

    Thanks for publishing my comment. My apologies about not putting my name. It wasn't intentional and certainly didn't mean to have my comment trashed!

    Also thanks for answering my question about the choice of wood. I think I can manage to lay my hands on one of those species. If nothing else, I can get some "white oak". I also learned about Hop Hornbeam for the first time. A lot of this is new information to me and I appreciate your sharing of it.


  8. Cadjedi (aka RS Johnston)December 22, 2010 at 10:30 AM

    All my best to you and yours in the Holiday Season.

    Another wonderful piece of work Chris. As always, practical and informative. Makes me want to dig out that piece of oak left over from my stair job. I will definitely be bookmarking this one for a future project.

    Yes, in agreement with a previous comment, the best blog on the net for this subject.


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