Hole machining in Mastercam

[lzerroug]

Hello everyone,

I have a little beginner problem with some parts i'm machining, they have a hole of 1.258 +0.002 -0.0. i use circle Mill on mastercam to rough and another seperate circle mill toolpath to finish with an M01 between the two,

Now the problem i have is that the hole is not completely circular, i measured many different values ranging from 1.250 to 1.265 in the same hole. i try to change my offset to get the right tolerances but it can't seem to have one value when measures,

i used my Lathe to create a kind of Go/Nogo, to quickly verify my parts, the go side has 1.255'' and the no Go has 1.563''. can i just rely on weather the go enters or not? or is my go way too small to give the right readings?

 

On a seperate question concerning machining tolerances, i have had to machine a part like the one in the picture with a tolerance of 0.003'', but as you see the space walls are too long, so i can't have only one constant measurement between the walls all along them. (PS: the units of the drawing are in millimeters) 

[Leon82]

Do you have the look ahead on in the machine? 

Are you using an overlap in circle mill?

how fast are you machining?

Your guage idea would depend on what roundness or workmanship spec they call out

[Matthew Hajicek - Singularity]

Have you measured the backlash in the machine?

[Guest]

Have also seen eggs machined when using R values instead of IJK values