[gogego]

Recently we had a job made from 8" x 1.6" barstock finished to OAL 1.5" x 2.98"ID , 8"x1" OD (flange), and 3.438" x .5" OD (hub) , the 8" od didn't quite cleanup all around.
In the first machine the part was drilled, faced, and the ID was cut to size, held in softjaws
In the 2nd machine the part was held on an ID collet faced to length, and both 3.348" & 8" ODs were cut.
In the 3rd machine the part was again held on an id collet 4 holes were drilled, 3 holes tapped, and a 3/16 slot was milled in the 8" x 1" portion of the part. from the od to approx. a 6" dia.
I am confident after several samples and many measurements the ID the size was not affected from the id holding,
After machining on the mill(3rd step) the ID shrunk .002", which is over our allowed tolerance. The 3.438" od also shrunk but was within tolerance.
The location of the shrinkage was directly in line with the slot and 1 of the 4 drilled holes
I think it is from slotting the part and am curious if anyone has run into similar situations with this type of material or any other, or was this a fluke.
An thoughts on this would be appreciated.

CHEERS

[timlkallam]

Some times material has stress in it.
You may need to rough it and leave everything .01 under size
and let the part sit overnight and then do the finishing.
I think you problem is with the slot cut it before finishing the
od and id.

I bought some chinese 7075 aluminum last year .
I needed about 1500 lbs of it .It was a dollar cheaper
than the alcoa aluminum .I thought great ill put an extra
$1500 in my pocket.
I ran a few hundred pieces the next day they were .0018
out of round, all were scrap. Sent the rest of the material
back and bought the expensive alcoa and everything was fine.
Lesson learned.