Run out

[Whaler]

I just ordered a dial indicator today to check the run out on my lathe and DP. I feel that I have a problem with my lathe drill chuck.
When I get it I have no idea what kind of run out is acceptable.
What do you use as a max number?

[LCHIEN]

You can affect the measurements greatly depending upon where you measure.
For example on a DP assume you place a 5" perfectly straight rod in the chuck.
If you measure the runout of a slightly bent quill at .002 right below the chuck then it might measure .010 at the end of the rod.

You have to take in the exact geometry of the situation and whether its bent or maybe just a bit non-concentric.

I'd say a DP runout of .002-.003 is probably pretty good measured right below the chuck. .005 is getting pretty marginal.
But I'm no expert. Also you need to take into accoount, an .002 off-center rod will go .002 to one side then .002 to the other side giving a total of .004 movement on the dial gauge. Do you count that as a run out of .002 or .004??? I'd call it .002 myself.

Another thing to consider is how much is "chuck slop". If you measure one number, take the rod out of the chuck and rotate it 60 or 180 degrees and re-chuck it. see if the number is the same and even high on the same side of the chuck. Do that a few times.