I was given a Luson drill press, model 18A, it says, 3/4" capacity. The chuck key that came with it has the right diameter shaft, 5/16", but the splined part seems to be a smaller diameter than needed. I can use it, been using it, it just seems as tho the splined part of the key ought to engage the notches on the chuck better than it does. Any ideas on getting the correct one? Thanks, Steve