The cabinet body, and it's shelves, are all six sided figures. Each carcase has permanently attached top & bottom shelves. Both of these shelves have to be identical. So there is a total of four (4) shelves that have to be cut exactly the same. Due to the angles and dimensions, it's hard to cut this shape on a table saw & get right once, let alone multiple time. So just how do you ensure that all four shelves will be identical?
The answer is to use a pattern. We carefully cut one shelf to size & shape using a cheaper material, in case we screw up & have to do it again. Once the pattern is created, we can then use it to lay out the four copies. These are then cut out over size using a circular saw and a straight edge guide. Lastly, the rough cut shelves are cut to final size & shape using a bearing guided straight bit in a router.
I had picked up a couple of quarter sheets of 3/4" thick MDF from Home Depot a week before the lumber arrived. Home Depot calls these "handy panels". They're a lot lighter than full sheets of MDF. One of these would become the pattern for the fixed shelves. The other will become the pattern for the adjustable shelves when I get around to cutting them.
I carefully laid out the shape of the top & bottom on one piece. The results can be seen in the picture below.
The next step was to cut off the waste on the left side of the pattern. Here's the set-up I used to make this cut. And yes, I'm positive this speed square is indeed square, and that the 45° corners are indeed truely 45°.
I lined up my guide with cut line. Then I clamped my speed square to the blank to make sure it wouldnt't move & to keep the guide square. Then the guide was clamped to the blank. The whole set up is sitting on top of 4 pieces of scrap to keep them elevated above the work surface. Next the speed square is removed & the cut is made.
Now I removed the waste in the upper right-hand corner of the blank. Here's what that set up looked like.
The speed square was clamped to ensure the saw would cut at a true 45° angle to the edge. I started on this side because I had the greatest confidence in the measurements of that corner.
After making this cut, I then cut the other 45° corner off using a similar set up. I wanted to make sure that these two cuts met at a true 90° angle. Here's what the pattern looked like after these two cuts were done.
Now it's time to cut off the short corners. To do this, I turned to my table saw. I set up the rip fence so that the saw would cut off the short corner opposite the long edge I placed against the fence. This takes advantage of the fact that the short corner is parallel to the long edge opposite it. The following picture might make this clearer.
After making this cut, I then rotated the blank 90° and repeated the cut with the fence unmoved. This is what the blank looks like after these cuts are made.
Just one cut left, to form the short edge parallel to the long front edge. This was done by adjusting the fence to the right value & cutting. The finished pattern can be seen below.
After cutting it out, I compared the length of the right short side to the left short side and they are within 1/16" of each other. This is close enough for me; an observer will never be able to see that difference. I am extremely happy with the way this pattern turned out. Thank you, Jesus!
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