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I'm rather pleased with the outer dimensions of the parts I'm printing; on a 1" feature, it seems that I can expect a tolerance under .005.

However, the inner dimensions are consistently off. If I have a hole that's supposed to be .5" diameter, it will come out .014 under, at .486. The .014 is pretty consistent (averaged over multiple tests).

What settings can I adjust to fix this? Is this an extrusion factor error (currently set to 115%, after extended testing)?

Check this out: http://hydraraptor.blogspot.com/2011/02/polyholes.html

g.

That is extremely helpful. Thank you!

Well, that did help, but it was only an adjustment from an average of .014 off to .012. It seems like my only option is to manually scale all internal features before exporting to STL.