Mathematical and Other Errors

Mathematical and Other Errors

In last week’s issue, Rob asked if other woodworkers had had mathematical errors compound their problems in woodworking projects. Your answers: yes. – Editor

“Does this question bring back memories! In Grandfather’s garage in Vinita Oklahoma, we ripped 1-in. x 12-in.’s down to maybe 3-in. for a contract for 100 mirror frames for the new ‘old folks home.’ I was there for the summer, and he thought I would be occupied by this most of the summer. I found out what ‘off by a little’ meant when I drilled a hole for the dowels that were to align and hold the corners of the frame together. After drilling at an angle (downward) I wound up doweling and gluing the first one to the plywood frame we built to align them. After chiseling the piece off the frame, the remaining 99 were done a different way.” – Riley Grotts

“As far as today’s request about mistakes made in the past, I probably have an abundance of them I could share. But the single largest batch of mistakes made involved a restoration of a 1965 vintage ’26 sailboat that I completed after five years of hard work. Had I known now what I did not know when I started, I could probably have done the restoration in two and a half years since I probably made enough pieces to restore two boats as I learned what worked and what did not.  What can I say? Woodworking keeps me humble.” – Jerry Carpenter

“While growing up, my dad hammered me with the idea of accuracy. He often told the story of “old Greenaway,” under whom he had served as an apprentice on the Victoria Railway in South Africa. The teaching point was how far out of alignment would one track be if 1/16-in. per foot error was extended to the end of the mile. I hesitate to put my math abilities on display, so I’ll let you do the math. What I really recall was when Dad ‘encouraged’ me to lay out the 1/16-in. error on the street in front of our house using the curb and his chalk line for presumably parallel rails!” – Roland Weisser

“Who hasn’t done the old use the one-inch mark for zero and forget to add one inch to the end?” – Bob Janousek

Some managed to still make their projects work, even if the math was a little iffy. – Editor

“Once I built a 4-ft. diameter waterwheel with 16 sections for my goldfish pond. With 16 sections, each joint was 22-1/2 degrees and therefore each cut had to be 12-1/4 degrees. Then, too, I had two sides that had to match with the paddles to make the 16 buckets. Due to my design, much like yours, I was able to allow for the little error. On top of that, the wheel had to be balanced when finished. When I completed it, I was well-pleased. All the buckets held water without any sealing and the wheel was so well-balanced, without having to add any additional weight, that with the ball bearing pillow block supports, the wheel would continue turning for 30 seconds after the water flow stopped. Now, with all that said, were there small cracks in places? Of course. I was using an older chop saw. The waterwheel worked really well for about eight years before the pressure-treated materials just finally gave it up. After a day of teaching school and driving a school bus, I would sit and watch the waterwheel turn from my recliner in the den. It was just like unwinding a spring that had become wound tight during the day.” – Charles Buster

And, for this reader, it wasn’t so much the math problems as it was the attention problem. – Editor

“My recent mistake wasn’t so much of a math problem as it was a lack of paying attention. I was building two foot placement aids for my daughter’s softball pitching instructor. (In February, all of his equipment was stolen from his pickup truck in his driveway.) He had commercially made equipment, but I offered a free, wood-made alternative. Anyway, I cut my pieces, six in total for two traps. Each one has two long sides of 18-in. and a spreader of 6-in. I decided to use dovetails as opposed to pocket screws and butt joints. I don’t have a jig made to cut box joints, so why not use dovetails? I cut my tails first and marked out the pins on the spreader boards. Cut all of the tails and pins and dry fit them, sort of. I never flipped the spreader the right way for the pins and never caught my mistake. So I made new spreaders, paying close attention to direction the second time around. They are made from soft maple that I salvaged from a desk someone was throwing away last summer, and applied BLO to the pieces. He was very happy with the foot traps.” – Kevin Hanes

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