Lee Michaels wrote:

I used to put together dumbells for commercial gyms many years ago. The
allen wrench provided for the dumbells were chap junk that twisted and died
in short order. Iused to buy the most expensive allen wrenches I could find
at an industrial tool supply house.


From my r/c racing days, I have a set of smaller sizes ground from
hardened drill blanks. It's amazing how bad a typical allen wrench can
be...