As parts get more and more complex, you will see part tolerances get tighter than ever. We’ve all seen the (+ -) .0001” size on a turn or bore, but what about concentricity? Quite often, it’s a call out that’s just plain missed. Catching the spec is one thing, meeting it is another.
Here’s some helpful ideas.
First of all, concentricity starts with “round” features. Remember, you cannot check for concentricity between two journals; maybe the spec is .0003” if one of the journals has .0004” run out in itself.
Second, boring the spindle tooling while positioned in the spindle, especially for the 2nd chucking, is a must. If you’re talking .001”, probably not needed, but if the print calls for .0004” concentricity or less, bore the spindle tooling and your success rate goes up.
Third, for the most demanding concentricity specifications, machine all the critical features together. This trick is pretty well understood in this industry but be careful, it’s not a 100% guarantee. There are a lot of factors that affect concentricity, Example: Balance, tool pressure, excessive part clamping pressures, to name a few….…
