To make the stand for my lathe, I had to use a lot of clamps and put my ten homemade clamps to good use. Up til now, these have been used rarely, so they haven’t been given a good workout.

While clamping a part on the stand, one broke:

Pretty loud snap! It startled me but really didn’t surprise me much. I knew the bar on these was the weakest part, especially where they are notched out.

Part of the reason for the failure could be in the selection of the wood used. Straight grained, defect free wood is best, but these were made from scraps so I couldn’t be too picky. The notches could have been a lot shallower as well – 1/8″ deep would probably have been deep enough. Making the bar thicker would have made the biggest difference, and this combined with the other two fixes would make the clamp much more rugged, without increasing the size significantly.

This is a good example of a situation where I should have built a prototype to test before going ahead and making ten of them. There is an arrogance that comes with designing something that can sometimes blind us to the potential problems. This is the first one to break but I’m sure it won’t be the last.

My newer design deals with this problem effectively by adding the strength of steel threaded rod to the bar and those clamps can exert significantly more force without the threat of breaking.

These are all valuable lessons learned, even for an old(er) dog like me.