[coldelectrons]

The rundown:

Machine: Taig CNC mill, Gecko G540, LinuxCNC with Mesa 6i25/7i76. VFD spindle. Tweaked, tuned, fitted. Minimal backlash, smooth motion in all axis.

Software: Qcad, CamBam, and G-Wizard.

Material being cut: Hardwoods and phenolics/composites.

I'm working on calculating the actual OD of my cutter, which has a nominal of 0.03125". Using a process of "cut, measure, correct, and repeat", I have come to a tool diameter of 0.02925", with which I can consistently (within 0.0002" with my gauge blocks) make slots or pockets at any target size.

HOWEVER...

Using the same calculated tool diamter, and the same part profile, the same roughing and finishing passes, but for the outide of a part instead of the inside of a pocket, results in a part that is consistently 0.0045" smaller than the target size in both the X and Y axis.

Simplest solution: Tell CamBam to leave 0.00225" stock on my finishing cuts for outside cuts.

I can work with this, but I find it perplexing that the same tool would have a differently OD wether cutting an inside or outside profile.

Do the more experienced minds here have any suggestions?

[redbaron88]

Are you cutting the same direction on both passes? ie climb milling or conventional