Concentricity vs. wall thickness

[ME2QE]

Hello All,

I have a small cylindrical part that has a hole drilled into it. I am trying to decide if the OD and the ID (really the diameter of the hole) should be called out as a wall thickness or a concentricity tolerance.

The part is molded out of plastic. I'm leaning towards wall thickness because the fixturing to measure it would be much easier to make.

Thanks for any help in advance!

 

[ME2QE]

Dingy2,

What my inspectors would do is put a pin gauge into the hole, zero off the pin gage, and then runout the OD.

Thats why I just wanted to make sure that the opposite works.

 

[ME2QE]

I've been going back and forth on runout and position with LMC. I decided to try position. I've attached a sample drawing.

assuming i dont want the wall thickness to fall below .0085, does this tolerance make sense? I don't want to submit this to a vendor and have them laugh in my face.

Thanks for all the help! You are all teaching me a lot.

 

[MechNorth]

My my my. First, the datum feature of size (FOS) must have a tolerance on it. Second, the outside diameter must have a tolerance on it. Without the tolerances for size, there's no way to tell what the minimum wall thickness could be. Third, the position callout must be attached to the FOS dimension callout. Fourth, the tolerance in the Feature Control Frame needs a leading-zero ... the nominal diameters are in millimetres (since they have a preceding zero), so the tolerance must also be in millimetres, and therefore must have a preceding zero also.

Jim Sykes, P.Eng, GDTP-S
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