We make a part out of an aluminum extruded tube 2 inch OD 1 inch ID. Have made them for years. Went to set it back up ( we have 8 Mazak lathes) and this time I could not get round bores to save my life. I cut the jaws to match the part OD I even cut the OD in the engine lathe to be sure of roundness. The part is chucked up on about 1/4 inch and I bore right up to the 1/4. Second spindle grabs the part it gets cut off and head two finishes the back side. We recycle the ring left in head one. Then I noticed the chuck jaws were not moving evenly. I grabbed the jaw and it moved quite a bit in and out. Checked the other machines and they did not have this movement. Well 10 years and 2 shifts the chuck was worn out for this type of chucking. Ordered a new chuck recut the jaws and I am back to perfect bores. So if you are having an issue like this you might want to check out the condition of your chuck.
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