I have a cylinder with a simple perpendicularity call out. The is a surface for datum A which the cylinder is to be perpendicular to by .001". When I check as called out on the print I get an output of .0002" to .0003". Looks good right? If I set the cylinder as a datum (C) the check the original datum plan to -C- I get outputs of .00161" to .00190". Still good but why the difference? Maybe the tolerance zones, flat vs. cylindrical? The reason this concerns me is it's an experiment by some of our engineers. The part is being machined on a Jig Grinder with a shim under one side of it, in this case .002". Is the possible answer the way the machining is being done, offsetting the datum surface rather the cylinder? Any thoughts or suggestions would be greatly appreciated.

Joshua A Farmer
Engineering Technician/ Inspector
Whirlpool Corporation/ Specialty Products Division, KitchenAid
1701 KitchenAid Way
Greenville, Ohio 45331
Phone: (937) 548-4126 Ext. 207
Fax: (937) 547-2850
Email:Josh_A_Farmer@email.whirlpool.com