The machinist's rule doesn't have a stud at zero to hook into a hole and take away the hole's bevel. However, there is a span gauge made that is metal, similar to a machinist's rule, and does have the stud. When checking a span on the press before drilling, I move the (not spinning) drill bit into contact with the gauge so I can best see exactly where the cut is going to be. I would rather that be soft plastic than metal, although the gauge is certainly softer than the carbide drill bit. Also, the metal gauge is straight instead of curved to the ball's surface so I would have to hold it in place while moving the bit in, just a little trickier. And, maybe most importantly, who wants to change what they've been doing for years? -- JohnP