Runout - Axial vs Radial

Symbol on the print is a single arrow.

We actually indicated a part this morning still in the machine. The feature that reports out of tolerance runout indicated to about 0.0005" on the indicator. I asked the machinist to move the indicator to the large cylinder since that is the datum and it measured about 0.004" on the indicator on the end to the large cylinder. I asked him to move the indicator to the other end of the large cylinder is it measured about 0.003" on the indicator.

The machine has the tail stock engaged and I think its moving the part when it engages.

{"data-align":"none","data-size":"full","data-tempid":"temp_23811_1669738835180_793"}
Put the part in a good "V" Block and check concentricity of the two diameters cut during first operation. They should be as good as machine can make them!
This will help determine where in process the problem occurs.​
HTH

acgarcia this is how to measure circular runout

Thanks for the info DAN_M as this always confuses me. Due to the size of my Datum A which is like 8 inches in diameter by 8 inches long, and my runout feature being about 3 inches in diameter but only like 1 inch long, it would only make a cylinder about .0.100" long because the the extension on my touch trigger head would crash into the part. I thinking about checking a part on 1 of my LSP CMMs. I might be able to make a longer probe to try and get a nice spread out cylinder. I haven't tried but I don't think that a short cylinder would make a difference compared to a circle.

I went ahead and reported true position for reference and you can clearly see the axial deviation. You can rotate the part 180 degrees on the CMM and my axial deviation move to the opposite directions so that pretty assuring. A machinist manager checked things out and found runout in the CNC. The drill that makes the hole and chamfer for the tail stock is slightly off center causing the tail stock to *** the part over. I haven't been asked to check anything differently or change anything like number or points or circles to cylinder yet.

DAN_M How would cross section 2 give you a value of 0.0008? Asking honestly.

min+max = 0.0008

acgarcia
mathematically, you should have the entire datum surface measured and then as much of the evaluation surface as you can. Only measuring .100 of a 3 inch long diameter will not yield correct or repeatable results

I would definitely look into using larger hardware if you need to keep this on the CMM or just do it on the surface plate

The example of shared with you, the result you would report is .0008 because its the distance between the lowest & the highest point of the “worst” analyzed cross section

DAN_M Thanks for the help. I got some work to do.

DAN_M Thanks for the help. I got some work to do.

goodluck