by another_jim on Thu Dec 18, 2008 1:38 am
It's an excellent question, and Randy's given a good answer. I would add that there's no real way of testing burr wear other than a cursory visual inspection. So if I were buying a used grinder, I'd budget in a new set of burrs.
Finally, a critical variable is burr alignment. That is, if the grinder is damaged, the upper and lower burr carriers may no longer be parallel. This can be tested by drawing a magic marker circle around the outer edge of one burr, then tightening them up so the burrs touch,. The ink will transfer in a full circle if the burrs align. If you only get a part of the circle, they are out of alignment. This can be a fault in the carriers and axle, so it requires more repair than just swapping burrs, and it is a red flag.
Obviously, if the seller allows the test, he is entitled to a higher price if the grinder passes, since you no longer bear that risk. My feel is that offering an extra $25 or so for the grinder if it passes this test may be money well spent.