I have been having trouble with a female taper I am machining in titanium.
the angle of the taper is 4 deg (2 deg each side), +/- 2mins 30secs.
The pocket has two parallel sides with a 2x .170" rads connecting the sides at either end. the overall depth of the pocket is .660".
I am using a custom made end mill with a 4 deg taper ground onto the tool, with a 2mm rad.
the problem is the results. In plastic test parts,the angle of the parallel sides comes out at - 32.4 secs while the curved end comes out at 1min 19.2secs. this is still within the tolerance.
When cut in titanium however the difference in the angle ranges from + 28.8secs for the parallel side, to +5mins 9.6secs for the curved side.
Can anyone explain the difference between the angles?
P.S.
The amount of material left to be removed from the semi-finish pass is 0.25mm.