Tramming a Jet 15
- So I just bought a 1986 vintage JND-15 at a flea market and after manhandling it on and off of my truck and hoisting it onto the stand I knew it was off... checking with a dial indicator showed about .017" between the high and the low side. Anyway, I measured the variation with the indicator attachments I happened to have on hand, then laid it out on the CAD on my laptop, and happy coincidence... the double jointed indicator bar I had to chuck in the collet put the indicator on a 6.5" diameter... which is as close to the corner to corner diameter (6.36) of my column base bolt pattern as makes no difference.
Anyway, shimming the column base by the indicator readings at the 45° locations brought me into perfect alignment within .001" (↓.0005) (after fixing my mistake of adding when I should have been subtracting, but I digress). Sure simplified the math! So if you don't happen to have a set like mine that just happens to be the right length, make your tramming bar the length of the diagonal radius of your bolt hole pattern, and tramming is simple .