Building a Prototype

Since my early days of being a youtube woodworking video junkie, there’s one project that I keep coming back to. One that I want to try. One that I think, “I could do that”. One that that seemed within a reasonable reach. One that didn’t require me to buy new tools. Patterned plywood. Thanks to Michael Alm (https://www.almfab.com/videos) for this obsession. The other draw is the materials. Basically everyone on youtube uses Baltic Birch plywood for like everything. You’d think the stuff was free, they go through so much of it. Personally, I have never used it. There isn’t a store local to me that even carries it on the shelf. Not the big box stores, not my local lumber yard. It’s also pricey. Not crazy, but certainly more than what you think a sheet of plywood should cost. What set all this in motion? Woodcraft (https://www.woodcraft.com/) had a sale. They had small 12″ by 12″ squares for only a few dollars each, so I purchased a handful, thinking pieces of that size would work for patterned plywood projects.

Once I got them, I couldn’t bring myself to use them. What if I mess up, what if it doesn’t look right? How could I waste actual Baltic Birch plywood? So to address this irrational concern that I had for a $5.50 piece of wood (that I got on sale for like $3), I decided to try it out on cheap(er) pine plywood from the big box store. That way I could use leftovers from my various shop furniture projects. I would make a prototype and see how it worked. Then, if my practice run worked, I would go ahead and make the real thing with the fancy plywood. First up was which of the many patterns to try. I eventually decided on one where each “piece” was made up of two pieces of plywood and one small piece of an “accent” wood. Of course for that I chose walnut.

I had no measurements to work with, so I just went with what looked right. I cut some plywood so that it was square on one side, and had a 45 degree bevel on the other. Two pieces like that got glued together using rubber bands for clamps. Once dry, I could fit a long square shaped piece of walnut “inside” the mitered joint, with glue and clamps to hold it in place. Once that dried, I had the basics of my pattern. I cut off a few small pieces (basically a cross section of the long piece I made) and started to fiddle with layout for a pattern. I quickly discovered that my blanks were not perfectly square and even if they were only off by a 1/16 or a 1/32 of an inch, once you placed several next to each other, the discrepancy compounds and before you know it, the pattern visually doesn’t line up anymore. Ugh. I need to be more precise. To correct what I had already made, I attached a sheet of sandpaper to a piece of hardboard with spray adhesive. This gave me a flat surface to sand on, and I clamped it to the table. Using digital calipers to measure the various dimensions until they were all within 1/64th. This was time consuming. I think the cause of the inconsistency is the throat plate on my table saw doesn’t sit perfectly flush to the table and on small pieces it can cause a wobble as the wood passes through the blade. Something I will have to address before building with the good stuff.

Now that my blocks were square and consistent, I could make slices. I got out the cross cut sled, set my stop block (https://kmtools.com/collections/frontpage/products/the-katz-moses-universal-no-deflection-stop-block-version-2-0-1) and made as many as I could with the blanks that I had made. I sorted the pieces in to the proper pattern, and then I realized, I needed to make a jig to glue these up – actually two of them, so I could glue them both up without waiting. This is a common theme in this project – having to make a jig for each step along the way. In this case, some scrap melamine boards served as the base (wood glue won’t stick to them), and I made a 90 degree angle with some scraps I covered with packing tape (so the glue won’t stick to them either). Finally, I could break out the glue and assemble them. Once assembled, some extra scrap with more packing tape, served as cauls to allow me to clamp everything nice and tight while the glue dried. This gave me a top and a bottom. Then I modified the pattern with the remaining pieces, and repeated the process to make a second top and bottom.

Next up, sanding. Yay, sanding. Starting with 80 grit to get rid of all the glue squeeze out, and all the way up through 220 to get them nice and smooth. At this point, I could have stopped and said, “yes, I can make a patterned plywood rectangle” and moved on to the baltic birch plywood. Instead, I decided to make them in to full boxes as my prototype, and then decide if I should do it all again with the fancy plywood, and some fancy hardwood for the box. Since it was a prototype, I simply used a piece of clear pine. First, I wanted to reduce the thickness, as 3/4 inch sides seemed too much for a small box. I ran them through the planer until they were 1/2 inch in thickness. Using the pattern plywood rectangles as the guide for the size of the box, I rough cut the pine to width and length on the table saw. Then I cut two grooves on the inside of each, one to inset the top, and one for the bottom. This was done on the table saw, using the actual plywood panels to test the fit.

Then I extracted my 45 degree angle sled from previous projects, and started making my miters for the box sides. Checking the size against the actual panels each time. I am more accurate doing it that way, then trying to measure and transferring the measurements. Once I cut all 8 sides (2 boxes, four sides each), I could lightly sand them, and then assemble. For this I used the blue tape folding method. Basically, you line up the four pieces in order, edge to edge with the miters facing down. Tape each of the joints together, and then flip it over. Then apply glue to all the joints, insert the top and bottom into their grooves, and then fold the sides around the top/bottom until they meet. Then tape that joint once it lines up. Lastly, I could not help myself and added some clamps.

Once the glue dried, I could extract the boxes from the clamps. They were a bit out of square. Something I will have to work on next time. I am not sure if it was the cuts, the assembly, or the clamps, that caused the issue. More practice is needed for this step. At this stage, I have two boxes assembled – but they have not been sawn through to “release” the lid. The miter joints in the corners are also not the sturdiest, so the next step was to reinforce them with splines. If you are not already familiar with splines, essentially you cut a perpendicular groove in the corner and then insert a piece of wood to fill the groove. It provides much more glue surface, and it is face grain to face grain, which also helps. Often splines are done in a contrasting color, so I decided to go with walnut, of course.

First, I would need to make another jig, a spline jig. Basically this is a 45 degree cradle that is attached to a sled, and holds the box, or picture frame or whatever, allowing you to pass the corner of the object through the saw to make a groove that extends evenly on both sides away from the corner. It also allows you to consistently put the splines in the same place on each corner of the object, in my case, the box. I hade done this before, but not in ages, and don’t know what happened to that jig, so I made another one.

My saw blade leaves a 1/8 inch groove (known as the kerf) so I needed to make splines that were 1/8 inch thick. I marked out some lines on a small piece of walnut, and cut the splines on my band saw. They were not consistently the right thickness, and I ended up hand sanding each spline, and fitting them in the grooves one by one. There were 24 of them in total. I might try this on the table saw next time. Now with the grooves cut in the boxes and the splines made, I could glue them all in place. This time, no clamps needed. Just a friction fit until the glue sets.

After the glue dries, the splines need to be flush cut. The box was too tall for my bandsaw, or my table saw, so I cut them by hand with a Japanese pull saw. This worked well for most of them, but because of its size, and my right handedness, and the spacing of the splines, some of them were very hard for me to get the proper angle and I nicked the sides a bit. This was another lesson learned, and a smaller saw recently arrived from (https://kmtools.com/collections/frontpage) so that I shouldn’t have this problem the next time. Now that the splines have been cut, I can sand the outside of the box to be sure all the sides are smooth. Once that was complete, it was time for the lid.

I like building boxes this way – you make a solid box, and then run it through the saw to separate the lid from the base. This way everything aligns, rather than trying to make a separate bottom and a separate top. I just about maxed out the capacity on the band saw, but it worked great. I actually marked out the cut line and then did it freehand. I was so worried about getting the fence square, that I simply opted not to use it and went very slowly. I cut both boxes this way. The results worked out fine, and I was able to sand it flat on the sandpaper that I had adhered to the hardboard. After another round of hand sanding all over the boxes, and softening the edges a bit, I applied a coat of boiled linseed oil. I had never used it before, but since this was a prototype, seemed like a good place to try it. The finish goes on very easily and it gave the box the look I wanted, while helping show off the pattern in the plywood top and bottom. I left the inside bottom walls unfinished.

Now I was in the homestretch. My plan for this box was to have a friction fit lid, rather than hinges, so I needed to create a liner – a think piece of wood on each of the inside panels of the bottom of the box (that I left unfinished, so the glue would still stick), that would extend up past the sides by about 1/4 inch. This allows the top to seat against it and hold the box shut. Simple and effective, if you can get the fit right. Once again, I needed thinner stock. I took a 3/4 inch think piece of pine, scrap from the outside of the box, and sliced it in thirds on the bandsaw. My cuts were not great, so I had to make a small jig to hold them up to the belt sander to get the thickness more consistent. Not perfect, but acceptable. Next time I may try to use the planer, with a sled to hold the small parts.

Nearly there. I cut the various pieces to size simply by sneaking up on the cut and test fitting about a zillion times. Finally, I could glue in the liner pieces and complete the assembly. Then some final sanding to round off and smooth the edges of the part that sticks up above the box side. Just like that, the boxes were complete. Now I could step back and admire my little project and think, “I wonder how these will look with baltic birch plywood?”. Probably about time to find out, and to put the lessons learned above, in to practice. I will be sure to post the results in the project section.

Thanks for reading along.