Can anyone help me to figure out why sometimes round elements in my cutting paths do not come out round I made a series of progressively larger holes all cut with a 1/8 tool, they look fine when round object are inserted into the holes they look good. the next thing I did is a pump housing with an oblong cavity 2,1/2 inches long 1,1/4 high 1/2 deep 5/8 radius thru 180 at either end with small 1/4 1/16deep pockets at the center of each radius wen I cut this the 1/4 pockets were obviously not round and when the 5/8 radius is felt with a finger a break or step can be felt. with the machine being new I had not entered any values for backlash so I checked for backlash and found.011 onthe y axis and.003 on the x axis I entered these values and recut the shape, this time where the small 1/4 journal pockets where simply not round now they resemble very rounded footballs or a square with very large radii on two opposite corners and slightly smaller radii on the other corners. I doubt it is a deflection problem as i am cutting in wood before wasting any more expensive material. I suspect it might be something to do with fixtures, but I do not know what they are or if they should be saved after each session or not. any help will be greatly appreciated .

                                                                                                       

Crusty,
    Can you post pictures of the cuts and the G-code? Also a sketch of what they should look like.

Brett

OK I've made a simple scetch of the 1/4 circle after I set the backlash I saved the scetch as a dxf file I will try to in clude the Gcode as well  I will also include part of the original drawing as a dxf let me know if you would like another file ext. also can anyone explain fixtures. I wil dig out the camera and take some pictures maybe I can get some good ones with my phone. thanks gotta go