Apr 2011
Ura-dashi (tapping out)
29 April 2011 Filed in: Tools
Finished the latest project …
And having a few days of relaxation to spoil daughter, who’s going to spend a few days with us from Tokyo, before I get started on the next major challenge.
A few people from one of the forums mentioned the ura-dashi process after reading my piece on tuning my plane, so I thought this would be a good opportunity to describe how I carry out this important step in the correct use and maintenance of Japanese planes.
The overall process consists of two parts: ura-dashi (裏出し) tapping out; and ura-oshi (裏押し) flattening the back.
Ura-dashi is normally done when the blade edge has been sharpened to the rim of the hollow (called the ura-suki 裏透き). It can also be done on new blades where the ura is not flat, either on one side or the other, or in the middle.
I’ll emphasize here that there are many ways of tackling this, and provided they work, each one is as good as any other. This is the method I use, and it works for me.
The first thing to do is check the cutting edge in the mouth. Eventually with sharpening over time the cutting edge will extend beyond the sides of the mouth (ha-guchi), and if this is the case you will need to file back or grind the mimi (blue arrows). You will know if this needs to be done because the shavings will become caught up in the mouth.
This plane is OK (green arrows), so on to the ura-dashi.
This photo shows where to hit with the hammer.
Too close to the edge will crack or chip the hard steel (hagane). I only tap on the back half of the blade bevel (kireba 切れ刃). In the case of this blade, the left-hand side of the ura-suki (hollow) is slightly deeper, so I needed to tap slightly more on this side. The key point here is to look closely at the blade, and find out what its characteristics are, if any.
I use the edge of my workbench to support the blade, as shown in this photo.
My workbench is Queensland maple, a reasonably firm hardwood. You can use any firm surface provided it gives good and solid support for the blade. I’ve rounded off the edge of the workbench for the blade, and filed the vertical corner to give a flat reference surface for my left forefinger. In Japan I used the end grain of a large board of keyaki (zelkova). Anvils, and short cut-offs of railway track are also used.
I use the corner of my gennou to tap out. This one is about 200 g, and it gives me good control. Any size or weight is OK provided you have control over where it strikes.
The point here is not to hit too hard. Many moderate taps is better than a few hefty smashes, which will almost guarantee a crack or chip. It also ensures better control of the hammer. You can tap slightly harder further away from the cutting edge, but the closer you get to the hagane, the gentler the tapping should be. And always ensure the blade is fully supported at the striking point, so move the blade rather than the hammer. That is, always strike at the same point, but use your thumb to move the blade to the left, right, up and down.
The next photo shows the result - an even distribution of tap indentations. And importantly, no chips or cracks. As I mentioned before, from this I continued to tap out with somewhat more bias towards the left-hand side because of the blade characteristics.
That completes the ura-dashi, now on to the ura-oshi.
I use my normal Shapton stones for ura-oshi. It is important to make sure that the head of the blade (atama) does not sag down as you flatten the back. So when doing this, you should feel as though you are lifting the head up slightly while applying the downward pressure to the edge, as shown in this photo.
You shouldn’t actually lift the head up though, as this would give the blade an unwanted back-bevel, just feel as though you are. Regularly check the shape and adjust the pressure as necessary.
This is the blade from my first plane I bought quite a few years ago, and this is what happens if you let the head sag. This was a source of great embarrassment for me at the College, and complete humiliation when my instructor looked at it and simply said “Hmmmmm”.
First, I give the back a few swipes on the 5,000 grit stone to check the condition of the ura-dashi, and make sure there’s an even protrusion. If that’s OK, I move to the 1,000 grit stone.
Another point to take care with is that as you move the blade left/right on the stone while flattening the back, you should also move it forward and back 10-20 mm so that a ridge doesn’t form near the cutting edge.
Then progressively through the 2,000 grit…
5,000 grit…
and 8,000 grit.
This is how it ends up. A clean even ito-ura.
The geometry of the blade has been changed slightly, so I also have to check how the blade sits with the chipbreaker, and adjust the chipbreaker as necessary.
From here it’s on to the normal sharpening process.
And having a few days of relaxation to spoil daughter, who’s going to spend a few days with us from Tokyo, before I get started on the next major challenge.
A few people from one of the forums mentioned the ura-dashi process after reading my piece on tuning my plane, so I thought this would be a good opportunity to describe how I carry out this important step in the correct use and maintenance of Japanese planes.
The overall process consists of two parts: ura-dashi (裏出し) tapping out; and ura-oshi (裏押し) flattening the back.
Ura-dashi is normally done when the blade edge has been sharpened to the rim of the hollow (called the ura-suki 裏透き). It can also be done on new blades where the ura is not flat, either on one side or the other, or in the middle.
I’ll emphasize here that there are many ways of tackling this, and provided they work, each one is as good as any other. This is the method I use, and it works for me.
The first thing to do is check the cutting edge in the mouth. Eventually with sharpening over time the cutting edge will extend beyond the sides of the mouth (ha-guchi), and if this is the case you will need to file back or grind the mimi (blue arrows). You will know if this needs to be done because the shavings will become caught up in the mouth.
This plane is OK (green arrows), so on to the ura-dashi.
This photo shows where to hit with the hammer.
Too close to the edge will crack or chip the hard steel (hagane). I only tap on the back half of the blade bevel (kireba 切れ刃). In the case of this blade, the left-hand side of the ura-suki (hollow) is slightly deeper, so I needed to tap slightly more on this side. The key point here is to look closely at the blade, and find out what its characteristics are, if any.
I use the edge of my workbench to support the blade, as shown in this photo.
My workbench is Queensland maple, a reasonably firm hardwood. You can use any firm surface provided it gives good and solid support for the blade. I’ve rounded off the edge of the workbench for the blade, and filed the vertical corner to give a flat reference surface for my left forefinger. In Japan I used the end grain of a large board of keyaki (zelkova). Anvils, and short cut-offs of railway track are also used.
I use the corner of my gennou to tap out. This one is about 200 g, and it gives me good control. Any size or weight is OK provided you have control over where it strikes.
The point here is not to hit too hard. Many moderate taps is better than a few hefty smashes, which will almost guarantee a crack or chip. It also ensures better control of the hammer. You can tap slightly harder further away from the cutting edge, but the closer you get to the hagane, the gentler the tapping should be. And always ensure the blade is fully supported at the striking point, so move the blade rather than the hammer. That is, always strike at the same point, but use your thumb to move the blade to the left, right, up and down.
The next photo shows the result - an even distribution of tap indentations. And importantly, no chips or cracks. As I mentioned before, from this I continued to tap out with somewhat more bias towards the left-hand side because of the blade characteristics.
That completes the ura-dashi, now on to the ura-oshi.
I use my normal Shapton stones for ura-oshi. It is important to make sure that the head of the blade (atama) does not sag down as you flatten the back. So when doing this, you should feel as though you are lifting the head up slightly while applying the downward pressure to the edge, as shown in this photo.
You shouldn’t actually lift the head up though, as this would give the blade an unwanted back-bevel, just feel as though you are. Regularly check the shape and adjust the pressure as necessary.
This is the blade from my first plane I bought quite a few years ago, and this is what happens if you let the head sag. This was a source of great embarrassment for me at the College, and complete humiliation when my instructor looked at it and simply said “Hmmmmm”.
First, I give the back a few swipes on the 5,000 grit stone to check the condition of the ura-dashi, and make sure there’s an even protrusion. If that’s OK, I move to the 1,000 grit stone.
Another point to take care with is that as you move the blade left/right on the stone while flattening the back, you should also move it forward and back 10-20 mm so that a ridge doesn’t form near the cutting edge.
Then progressively through the 2,000 grit…
5,000 grit…
and 8,000 grit.
This is how it ends up. A clean even ito-ura.
The geometry of the blade has been changed slightly, so I also have to check how the blade sits with the chipbreaker, and adjust the chipbreaker as necessary.
From here it’s on to the normal sharpening process.
Comments
Tuning my finishing plane
19 April 2011 Filed in: Tools
The weather has been a bit all over the place over the past few days, and while I was waiting for the finish on a couple of frames to dry, I checked my finishing plane for movement. The changing weather had affected it, and it needed to be tuned. It wasn’t too bad, and normally just a couple of minutes with the dai-naoshi kanna would have fixed it, but thought I would completely tune it from scratch, and put the photos here to show how I do it.
This is my finishing plane for rails, stiles and narrower pieces, so I have three touch points, shown in the next photo: what we would perhaps naturally call the front of the plane but is actually the back (daijiri 台尻) - 1; the area forward of the mouth - 2; and the front (daigashira 台頭) - 3. The surface between these three points is slightly concave so it doesn’t touch the wood being planed. The plane therefore “glides” along the planed surface on these three points. Because this is my finishing plane, these concave areas between the touch points are relieved only very slightly.
This photo shows what I use for tuning.
Yes, it is sandpaper, and it works well. 220 grit sandpaper stuck on to 16 mm MDF, the plane being tuned, my dai-naoshi kanna (a scraper plane), and a small gennou for removing the blade. I also use a chisel.
First, I retract the blade slightly so it’s protected from the sandpaper, but down far enough so that it still applies the normal tension to the dai. Then I completely flatten the sole (dai shitaba 台下端) on the sandpaper using a normal planing motion.
If you’re concerned about grit from the sandpaper attaching to the plane (it didn’t seem to worry any of the master craftsmen instructors at the College), you can wipe the sole with turpentine or the like after using the sandpaper.
Once the sole is perfectly flat, I then start on the concave areas between the touch points.
First, the parts to the left and right of the mouth. I simply use a chisel to carefully pare away a small amount of wood shown by the red arrows.
I now work on the concave area between touch points 1 and 2. To start, I simply turn the plane around so it’s perpendicular to the sandpaper, and carefully sand the required area. Care must be taken not to sand too far either to the left or to the mouth.
I then use the dai-naoshi kanna to cleanup and refine this concave area. As an aside, I always sharpen the dai-naoshi kanna blade before I use it. The sharper the blade, the better, cleaner and faster it removes fine scrapings of wood.
Next, I work on the concave area between the mouth and touch-point 3 (daigashira) with the dai-naoshi kanna.
I also use a sharp chisel to scrape away wood from near the mouth. This gives more control close to the mouth, and prevents the possibility of accidentally scraping away parts of touch-point 2.
Once I’ve finished this, I check the sole lengthwise, across and diagonally. The area in front of the mouth is especially important.
After I’ve finished the dai, I check the blade. I sharpen often during use, so I have to tap out (ura-dashi) quite regularly.
Here, the flat (ito-ura) is becoming quite narrow, so I’ll need to tap-out at the next sharpening session.
This is my finishing plane, so I progress through the grits up to 12,000. I use Shapton stones - 1,000; 2,000; 5,000; 8,000; and 12,000. For my non-finishing planes, I stop at the 8,000 stone. After sharpening I put the blade back in the plane and give it a try to make sure the tuning was successful.
And as they say…
The proof of the pudding is in the eating.
This is my finishing plane for rails, stiles and narrower pieces, so I have three touch points, shown in the next photo: what we would perhaps naturally call the front of the plane but is actually the back (daijiri 台尻) - 1; the area forward of the mouth - 2; and the front (daigashira 台頭) - 3. The surface between these three points is slightly concave so it doesn’t touch the wood being planed. The plane therefore “glides” along the planed surface on these three points. Because this is my finishing plane, these concave areas between the touch points are relieved only very slightly.
This photo shows what I use for tuning.
Yes, it is sandpaper, and it works well. 220 grit sandpaper stuck on to 16 mm MDF, the plane being tuned, my dai-naoshi kanna (a scraper plane), and a small gennou for removing the blade. I also use a chisel.
First, I retract the blade slightly so it’s protected from the sandpaper, but down far enough so that it still applies the normal tension to the dai. Then I completely flatten the sole (dai shitaba 台下端) on the sandpaper using a normal planing motion.
If you’re concerned about grit from the sandpaper attaching to the plane (it didn’t seem to worry any of the master craftsmen instructors at the College), you can wipe the sole with turpentine or the like after using the sandpaper.
Once the sole is perfectly flat, I then start on the concave areas between the touch points.
First, the parts to the left and right of the mouth. I simply use a chisel to carefully pare away a small amount of wood shown by the red arrows.
I now work on the concave area between touch points 1 and 2. To start, I simply turn the plane around so it’s perpendicular to the sandpaper, and carefully sand the required area. Care must be taken not to sand too far either to the left or to the mouth.
I then use the dai-naoshi kanna to cleanup and refine this concave area. As an aside, I always sharpen the dai-naoshi kanna blade before I use it. The sharper the blade, the better, cleaner and faster it removes fine scrapings of wood.
Next, I work on the concave area between the mouth and touch-point 3 (daigashira) with the dai-naoshi kanna.
I also use a sharp chisel to scrape away wood from near the mouth. This gives more control close to the mouth, and prevents the possibility of accidentally scraping away parts of touch-point 2.
Once I’ve finished this, I check the sole lengthwise, across and diagonally. The area in front of the mouth is especially important.
After I’ve finished the dai, I check the blade. I sharpen often during use, so I have to tap out (ura-dashi) quite regularly.
Here, the flat (ito-ura) is becoming quite narrow, so I’ll need to tap-out at the next sharpening session.
This is my finishing plane, so I progress through the grits up to 12,000. I use Shapton stones - 1,000; 2,000; 5,000; 8,000; and 12,000. For my non-finishing planes, I stop at the 8,000 stone. After sharpening I put the blade back in the plane and give it a try to make sure the tuning was successful.
And as they say…
The proof of the pudding is in the eating.
Couple of relaxation pieces
09 April 2011 Filed in: Art
After finishing the landscape piece above, I needed something less taxing to give my mind a bit of a break.
As an aside, I used eight different patterns in the piece: kuruma-kikkou, dahlia, kaza-guruma, rindou, kawari-yae-zakura, yae-zakura, yae-asa-no-ha, and kawari-asa-no-ha. All these patterns are described in the Patterns 02 section.
The two pieces I finished next are asa-no-ha in a diamond (hishi-gata) jigumi. A very simple pattern and design, but I think quite effective in their simplicity. Wife Mariko designed the first piece, and the second is my design effort. Kumiko timber is Huon pine, and the frame is kauri. For these frames I used a gloss finish, rather than the usual satin finish.
Over the next week or so I’ll add a tools section detailing the tools that I use in my kumiko-zaiku. If I can get it to work properly, over time I’ll also add short videos on how I use the specialist tools, and also bits and pieces on Japanese tools, especially hand-planes, in general.
[Sleeker_special_clear]