Making a Japanese Plane

Words and photos by Terry O'Loughlin

I saw the traditional Japanese shoulder plane pictured above in AWR#51 in Iain Green's story on the Shuko-kai group and was immediately taken with it. I liked the simple lines, the self-effacing wedge and the elegant escapement for shavings.

Armed with a 19mm shoulder plane blade and a piece of southern blue gum (Eucalyptus globulus) I set about making a copy. Having made it, I realised that there was nothing in the construction that would seriously challenge any experienced woodworker.

The first step is to select a piece of suitable timber: hard and close-grained. Any number of native species fit the bill, to say nothing of the traditional beech, rosewood or ebony.

Marking out

Dimension your timber to length and height, but leave it a bit oversize in width. Ensure that the sole is square to the sides. The grain must run out towards the back on the sole to avoid catching, so clearly mark which is to be the front. Then mark out the rear of the mouth across the sole, up the sides at 50º and across the top of the plane.

This marks the rear of the slot for the blade and wedge. Now mark the front of the slot, 24mm forward of here. From there mark down the sides at 60º for the position of the front of the wedge. Mark out the front of the mouth and the escapement and the chamfer around it. Final adjustment of the shape will come later.

Now for the slot for the blade and wedge. The shaft of the blade is 6mm wide. To allow for lateral movement of the blade, the slot can be 8mm (5/16”) wide. Mark this on the top of the body with a mortise gauge. Then mark the cut-out at the back of the body, and a curve (about 22–25mm diameter) at the front for the round-over of the top of the plane. You can continue marking the round-over along the sides to just behind the blade.

Cutting out

You will find that a 1” or better still a 25mm forstner bit will fit in the escapement. Use this or a spade bit to remove most of the waste. Saw through the mouth, but leave it undersize for now, no more than 5mm wide. Using a 3/16” thick blade, the mouth will end up being about 6mm. With a coping saw, carefully remove the rest of the escapement, allowing a little for smoothing later.

To begin the slot for blade and wedge, mount the body in a drill press vice and align the frog line on the side with a ½” or 6.5mm drill bit, preferably a forstner or brad point bit. Place a square on the drill table to check.

Now drill through to the escapement. You will find that the bit may slide down a little before fully engaging in the timber. Lower the body 10° to line up with the front of the slot against which the wedge will bear. Start the drill back from the line to allow for any movement before the bit goes in. Again drill through to the escapement. With chisels, remove the waste between the drilled holes and widen and square up the slot to the full length and width.

If you have a pair of planemaker’s floats like the ones below above this will simplify the process, but chisels and files will do the job. With files, be careful unless you have one with a safe edge; it is safer to file one surface at a time.

Trim and fit

The wedge will grip front and back, but must not be a tight fit at the sides so it does not split the plane body. Cut it out oversize, but narrow enough to fit the sides of the slot. Now you will need to flatten the frog, firstly with a chisel or the edge of a file. Then with a warding file align the surface at the mouth end for the spade end of the blade. Take your time over this, since a flat frog is essential to ensure the plane works effectively. Be particularly careful not to allow the file to rock. As you approach flatness, you can begin widening the mouth, but keep it tight. It should be only wide enough to let a shaving through.

Trim down the wedge enough for it to start entering the slot to hold the blade. Try out the fit as you go, but do not finally dimension the wedge. Only when you are sure that the blade seats firmly on the frog can you plane down the wedge to reach to the spade end of the blade as in the diagram and the photo above.

Now with a round file finish the inside of the escapement opening. Try to achieve a sweet curve. Then work on the chamfer, again with a round or half round file. This has little to do with the operation of the plane, but is important for the appearance.

Finishing off

Having finished the insides, the outside work is simple. Firstly, saw the cut-out behind the blade and clean it up. The slope behind the blade is at 90º to the blade pitch, and is 10mm deep. Round off the rear corner. Now make the curve on the top from the blade to the front. Plane most of curve and smooth with sandpaper. The body is oversize, but must be carefully planed down to be a few fine shavings narrower than the blade. This will allow the plane to work into corners.

All that remains is fine sanding all over, and your choice of finish. I used a couple of coats of oil and finished up with wax.
Blades can be obtained from: HNT Gordon www.hntgordon.com.au
Planemaker’s floats are available from: Henry Eckert www.henryeckert.com.au

This story was first published in issue 54 of Australian Wood Review.
Terry O'Loughlin makes furniture and woodworking tools and is based in Canberra.