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:
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:
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:
Once the saw cuts were made, two for each ramp, out comes a skinny paring chisel:
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:
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:
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:
Thanks for taking the time out to check in on things here, and I hope to see you again soon. –> go to post 2