A weekend class was just completed at MASW, Making a Kumiko Box by Mike Pekovich, a great class and a great teacher. The box was not quite completed in class, so was finished this morning by lid fitting, sanding, shellacking, and waxing. The planned Kumiko was a hemp leaf pattern, the hemp plant signifies growth in Japan. Mike prefers making boxes with a purpose and when providing them as a gift they are often filled with chocolates or other surprises. This is in line with Mike's philosophy on making: Each item made is an example of our "ability to connect to people with the things we make".
We began with grooved and rabbeted cherry for the box sides. A dado for the bottom, a rabbet for the Kumiko panel, and a second dado for the eventual lid joint. The inside of the box was finished at this point, minimizing the impact of later glue squeeze out. The inside face of the board was sanded with 220 and then 400 grit sandpaper wrapped around a sanding block. The rabbet was sanded as well as the bottom. Inside corners were slightly rounded.
Shellac was used for the finish. Mike recommends unwaxed shellac, either a shellac like Zinsser Seal Coat or clear shellac. The latter after sitting usually has a cloudy layer at the bottom of the can, the wax. The top clear layer can be used as it has little wax content. The material in the can was diluted 1:1 with ethanol. The inside face of the wood, the bottom and top edges were all coated with shellac. This first coat raises the finish so the shellacked surfaces were lightly sanded with 400 grit paper. This first coat was followed by a second.
The sheet of plywood for the bottom was also sanded. The box has pretty paper in the bottom and under the Kumiko. The box bottom was sprayed with adhesive and the oversized paper was applied. The edges were burnished a bit to insure good adhesion. The excess paper was cut off with an Xacto knife.
The second task was the miter cuts for the box sides. Before cutting some ghost lines were drawn on the outside face, so the sides could eventually be returned to the same order. The miters were cut on a table saw with a very nice sled from Mike for cutting the sides to perfect dimensions. The blade was set precisely at 45° by cutting four pieces of scrap and checking their fit by taping them together and forming the box. If the resulting "box" is open the blade is less than 45°. The four corners amplify any angular error, so precision is important for a nicely fitting box. Four shots of the miter sled are shown below. I might want to replicate it at some point.
An important note for using a clamping sled for this or any other angled blade cut, the clamp should be on the high side of the blade. Ideally the cut off piece of wood under the blade falls away from the blade after it is freed. Mike's sled was two levels, high on the side above the blade. The piece was cut alternating between long and short, allowing for a continuous grain pattern. The outside of the board was always oriented face up. The miter remaining on the board after cutting off a side was removed before cutting the next side.
In class we worked on both the Kumiko pattern and the box at the same time. In this write-up all of the Kumiko work is described in one block, so I will continue with the box work. The ghost lines were used to put the four box sides in order. The sides were taped together with blue, somewhat stretchy tape holding the pieces close together. Two pieces of tape were used for each joint. The pieces were held against a straightedge during taping. The fit was checked with the bottom in place to make sure the bottom is a loose fit.
Gaps were common at the corners, either shaped like two bows joined at their ends or like two bows touching at their midpoints. Both indicate slightly bowed starting stock. Minor gaps were taken care of during glue up. A band of glue was run in the corner of the vee between boards. A small brush spread this glue to cover all of the end grain. The box was folded up around the bottom with care taken so the last joint is well aligned. The box was left to dry sitting upside down, so any glue squeeze out does not run down to the paper covered bottom.
A 45° sled was used to cut the three splines in each corner. Two stops in the box set up the three cuts. Depth of the spline cut was set so it did not penetrate the inside corners. The strip of wood for the splines should be checked for fit prior to cutting it into the needed twelve splines. It is easier to sand the one long strip than twelve splines. A miter box was used to cut the splines by hand. They are cut so the grain runs parallel to the uncut edge of the triangle.
The splines were dipped in glue and pressed into the cuts in the box. (Wet hand on the splines and dry hand on the box!) After drying most of the spline was cut off with a band saw. The band saw had a straight edge on the inside of the blade and the blade fit in a notch in this edge. The spline excess was quickly removed in this fashion, leaving about 1/16" of material. The belt sander used gently and with care removed the remainder of the splines. The box was held against a stop during sanding both to provide support, but also to keep the box from rotating and sanding only one edge. Sanding was always done equally from both directions by flipping the box over. Sanding was continued until the glue halos from gluing the splines disappeared.
The box lid was cut off next. The blade in the table saw was set to just touch the bottom of the extra dado. A challenge of separating a box from its lid is the box collapsing during the last of four cuts. To minimize this the depth of the cut was set so the blade barely finished the cut. The short ends were cut first and spacers were taped into these cuts. The long sides were then cut. It is important not to pull the sled back and cut the box a second time, so the box was lifted from the sled prior to pulling the sled back. An Xacto knife was used to finish separating the lid from the box.
Fitting the lid was the next order of box business. Squeeze out in the corners can give a false tight fit. This can be verified by checking the fit of each side at an angle. If all fit the culprit is glue in the lid corners. This is removed carefully with a chisel. Another common problem are steps in the corners from the four cuts used to separate the lid. Sanding or a corner plane will flatten these. If the lid fits, but one side is slightly proud and the opposite sits a bit low a corner plane is used to trim the ridge holding the box. Ideally, a very thin and even cut line will run around the periphery of the joint. One should either strive for a press fit, so the box owner needs to hold both the bottom and the top to separate the parts or more commonly a loose fit, where only the lid needs to be touched. Binding in just one location should be avoided. I chose a loose fit as that is what my lid gave me.
With the lid making a pleasing fit and joint the bottom of the top was sanded with 150 grit paper. A sanding stick was used to sand the top surfaces of the box. The top and bottom edges of the lid joint were very lightly rounded providing a consistent shadow line. As Mike said, "There is no sense hiding the fact that this is a lid on the box." All box edges that will be touched were slightly chamfered. The sides were sanded with 220 and 400 grit. The splined edges were touched once with 400 grit just to take off the sharpness.
The finishing continued with shellac. Again a 1:1 mix with ethanol was used. The first coat was followed by a light sanding with 400 grit sandpaper. This was followed with four more coats of shellac, all applied within minutes of the previous coat as the ethanol evaporate that quickly. After a more prolonged drying time, ten minutes, a coat of paste wax was applied with #0000 steel wool, following the grain. The box was buffed with a soft rag. The Kumiko panel was fit in the lid and the box was complete.
Many lessons were learned from the box construction, but I went for the Kumiko. This began with strips of white pine cut to size and notched for this design. These were glued together, though only gluing the outside joints. The panel at this introductory stage is shown below.
Mike provided sets of fixtures for the students to use for accurately and repeatably cutting the pieces making up the pattern. He also sells these as a set. A chisel was used to make most of the cuts with a Japanese pull saw used to make the rest. The cuts with the saw were all rough cuts. The chisel is held between the fingers with a finger or thumb on the back of the blade. The chisel is pressed so either the face or the edge are held against the fixture during the cuts. Multiple cuts each shaving off a bit of material are used to plane the wood to the correct angle.
The diagonals were the first pieces cut and installed. (Clean hands are important as the pieces are not sanded on their faces!) A length of the pine (1/8" X 1/2") was held on the grid and marked about 1/16" long. It was cut at the mark with the saw. The remaining seven diagonals were cut to the same length.
Both ends of the diagonals end in 90° points so the 45° fixture is used to cut the ends. The ends are cut so the point ends up centered on the width of the part. A gentle press fit is desired. After cutting an end the correct fit was snuck up on with repeated cuts. Once it and a second piece fit well at right angles in two blocks without deforming the squares, the remainder of the pieces were cut to the same length. All of the these pieces were put into the grid.
The next parts were made in two stages. One end of these parts fits between the diagonals and the grid sides, so the internal angle is 22.5°. The fixture for this angle was used. Thirty-six pieces were cut 1 1/16" long, four extra and longer than needed. Only the pointed end fitting into the corner was cut on each piece. Following this cut, one complete 67.5°bevel was cut across the end, leaving the part still too long as seen below.
The complete bevel was then trimmed on both parts until they fit. Care was taken, removing only shavings, as the change is doubled. Once the gap vanished the rest of the pieces were cut to the same lengths. Some of these parts in place are seen in the first photo below. Pencil lines were drawn along all of these ends. These pencil lines will eventually be joined. The second bevel on this face is the same angle, but in this case the point of the end should not be centered, but instead the pencil lined face should be about one third of the width of the wood, with the cut made second making up 2/3's. All parts cut in this fashion are shown in the second photo below.
These last parts in the grid are loose of course. The final piece serves to lock the entire square in place. Cutting these pieces required some custom fitting. Both ends ot these short keys are cut with 45° bevels producing a 90° end. One part was iterated and tested until it fit tightly in one square. The length of this part was repeated in a second and it was also tested until a square was found to fit. Iteration continued, though many were fit with the first setting of the fixture's stop block. The last few were fit locking all of the squares in place, as seen below. The parts were all tapped flat to the table using a block of wood that was slightly smaller than the dimensions of the grid square.
The Kumiko panel required only a bit more work before it was completely finished. The first step was gluing all of the pieces in place. Normally the pieces would be removed square by square, glue applied, and the pieces put back together. A student suggest and tried using superglue instead. Mike was impressed, tried it himself and the rest of the class followed suit. A small amount of superglue was poured into a container. A toothpick was used to place drops on the joints. The medium consistency glue wicked into the joints and quickly dried. No accelerant was used.
The tabs were sawed off and then the outside sanded. Sanding was continued until a tight fit in the lid was achieved. The grid was sanded on the show face with 150 grit paper. Any holes were touched with a dab of white glue and the sanding repeated. The unsanded face, like the bottom has decorative paper attached. Glue was sprayed onto a piece of cardboard and the grid pressed into the glue. The grid was then set on the paper and the paper cut to fit. This completed the lovely Kumiko panel.
