How To Measure Backlash and Linear Compensation ??

[Joe_Leen]

How does one physically measure the backlash and linear compensation on a Bridgeport Series II Interact II Mill ?

Need the machine to run as accurate as possible so need this info to set the parameters.

... Just read about using a dial gauge http://www.cnccookbook.com/CCBacklash1.htm to directly measure backlash, but what about the linear compensation ?

Thanks,

Joe

[machintek]

Does your control support linear compensation?
For backlash, I put in a value of .005 inches, cut a circle with a spring cut, measure the circle and i can see the steps as the axis changes direction. This I subtract from the .005 inches and it should be pretty close. Anytime I see a backlash value exceeding .0035 inches, I know that axis has a problem. Also older machines may have the backlash different between the center of the table where the machine is typically used more vs the ends of the table. A ball screw regrind might be necessary.
Pitch error compensation requires a step gauge or a laser.

George