tool offset off mpg or not

[wayneswagon]

i have a new to me 1995 vmc15xt. i have only ran three parts so far all 3d surfacing the finish seems pretty good. the problem i have is on all three different parts new tool setting each time they have been off .003 or .003 to deep i used the handweel twice.Then thinking it was the mpg the the third time i used jog mode. any ideas why i would be off there is no z in the fixture offsets

Thanks Wayne

[DareBee]

ballscrew or thrust bearing backlash will do it.
Setting the tools at different spots on the table will do it.

Also are you setting the tools with the spindle at operating temp?

I have noticeable growth (from cold) after running the spindle at high speed for 1/2 hour.

[wayneswagon]

i looked at backlash tonight i reset backlach to zero on z axis.Then checked it it was off .0016 so i enterend that number as 16 and basicly nothing happened. I rechecked it and it was still about .0015 what would be the next thing i should check thrust bering ? and how ?

Wayne

[denmar]

Set a mag base with an indicator at the botton of the Bs, jog up and down ,
Also hit the E stop and grasp the BS u will fill if is too loose or tight.