Design for Tolerance
This is my own take as to when and where tolerance should be applied. My experiences are from the 4 months I has working at crafter’s lab, which highly involve me making wooden boxes like shape.
This was a problem when I tried to assemble a box for a trophy, which needed to look amazing in both craftsmanship and accuracy. And what I had was definitely not a good crafted box.
Therefore, to actually be able to call this a trophy worthy box, I need to improve my craftsmanship. And what better way than to start from the source, as I realized a lot of my cuttings are too “perfect“. Therefore, if I make a mistake somewhere at the start of the process, the result after suffers.
From the thinking above, I realized that tolerance needs to be designed from the top of the process down. The further along the process a part is needed, the more tolerance it needs.
Take the trophy box again for example. How it is assemble is as shown below.
The first piece doesn’t need any tolerance, if anything, it needs minus tolerance, buts that’s beyond the scope today. But to align the first to the second piece, some human errors could occur. It could be aligned twisted, off centered, skewed and so on. Therefore, 2 of the edges needs to be longer and trim short after it is secured together. However, in my workshop, only one of the edge is longer as due to the limitation of our tools, we could trim another edge. But after these alignment, The 3rd, bottom piece, needs to have even larger tolerance to account for all the possible misalignment that could have happened during the alignments of pieces all before.
Why we don’t put the tolerance in the thickness but rather length is because the tools we have, and it is also to get an even length rather than thickness, due to the amount of materials needed to cut. But how we are trimming the edges is with a router, and a router can’t eat through a lot of material at once. Hence, it is both easier and beneficial to cut the edge than face.
