Introduction: Kanna - Japanese Woodworking Plane
Here's how I made a Japanese woodworking hand plane, or kanna.
All you'll need is a kanna iron, which you can find online, some quarter sawn oak, and a few basic hand tools.
I've included the plans for mine, but you can make a longer body (dai) to use it as a jointer, or a shorter body to work more like a block plane. Also, bear in mind you will need to adjust the throat width according to your iron.
Let's get started...
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Step 1: Rip Dai From Stock
Use the iron to mark the width of the dai on the stock, allowing 3/8" each side. Try to align the dai so that the growth rings are symmetrical across the width, and the same at each end (this isn't necessarily parallel to the side of your stock, but should be reasonably close). If you use a full live edge board like I did, then your dai will fall near the centre.
Rip the dai from the stock, using whichever saw you prefer. I used a hand saw, which was probably quicker than getting out a circular saw, or jig saw, or tensioning a band saw.
Step 2: Square the Dai
Before marking out, it's important to make sure the dai is square all round.
If you have a hand plane this will be easy, but if not you could use a rasp, belt sander, or similar.
Flatten one face to begin with, then using a try-square work the sides. Mark the final thickness around the sides, and bring the opposite face down to the thickness line.
Step 3: Rough Out Throat
Use the plans to mark in the shape of the throat on the sides of the dai.
The throat will be about 3/8" narrower than your iron, and we'll deal with that later.
You can bore a series of holes through the dai, where the throat intercepts the sole of the plane (forming the mouth). Then use a chisel to chop out the the sloped ends of the throat, and straighten the throat sides.
Step 4: Iron Grooves
The iron is slightly tapered in it's length, and is held in place, in grooves cut into the sides of the throat, as it gradually wedges tighter when tapped down. The cutting edge will just emerge before it becomes too tight to knock the iron further into the dai.
To mark for the grooves, I planed a short lath to the same tapered thickness as the iron, and used it to knife in a line the correct distance from the bed of the throat (the slope that is less steep). Cardboard cut to size would work just as well.
Now use a small saw to cut each edge of the groove. If you don't have a small saw, you could use a hack saw, inserting the blade in the throat before installing it in it's frame.
Finally, use a chisel to remove the waste from the grooves.
The iron should now insert partially through the dai, tightening in the grooves. It should not tighten in the width though, as this could split the dai, so deepen the grooves a bit if it does.
Step 5: Seat Iron
The plane will work better if the iron is seated tightly across the whole bed, as this will dampen vibrations.
To seat the iron, wipe graphite from a pencil across the back of the iron, and place in the dai. Now push the iron as far in as you can, and wiggle from side to side. Withdraw the iron (hold the to of the iron while tapping the rear of the dai with a hammer) and any high spots on the bed will be marked with the graphite. Use a chisel or scraper to remove a little material where the bed is high, before re-testing, until the graphite is marking most of the bed.
Step 6: Try It Out
Try taking shavings. Start with the cutting edge inside the mouth, and then lightly tap the end until it can just be seen emerging. Increase depth of cut by tapping the iron in further, and reduce cut by tapping the end of the dai. Adjust laterally, if shavings are thicker on one side, by tapping the top of the iron either left or right as necessary).
- Iron can't be driven in far enough for cutting edge to emerge from mouth
Grooves are too thin. Remove iron and widen grooves slightly with a sharp chisel
- Cutting edge emerges from mouth before iron starts to tighten in grooves
Grooves are too wide. Paste a sheet of paper over the entire bed (right into the grooves)
- Cutting edge emerges from mouth, but won't take a thin shaving
Sole of plane not flat. Wipe pencil over whole sole, then rub on sandpaper stuck to a flat surface, until all pencil marks removed.
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