By Ken Levine, senior electrical engineer
I have a Sears Craftsman hand-powered, reel-style lawn mower. The handle is shaped like a U. It connects to the lower U-shaped piece with four bolts (two on each side). The handle and lower parts are made out of metal tubes, about 1/2″ diameter and about 1/16″ wall thickness. Where the handle bolts to the bottom part, the handle is flattened. I bought this lawn mower two years ago to replace the hand operated reel mower that worked for 30 or 40 years. Unfortunately, parts were no longer available.
About six months after buying the new one, the handle sheared off at the top bolt. Sears replaced the lawnmower, but only after claiming my yard was larger than what the lawnmower was designed for. I tried to explain the replacement would also break because the design is faulty. The replacement mower lasted over a year. Yep, you guessed it, the handle sheared off at the top bolt. Still under warranty, so Sears will give me another faulty mower. The Sears design monkeys must not understand how to calculate mechanical stresses, especially in flattened tubes that have bolt holes drilled in them.