We are doing a short run project for a company. We are a stamping factory. They want to stamp out a flat "V" shaped retention spring out of 0.018" thick steel and measure 0.010" flatness,
unrestrained. I usually deal with material that is thicker than this. Anyone have any ideas?
If the engineer is silly enough to call out a flatness on an .018" part, then as long as the maximum surface deviation is under .010", it should suffice as a reportable data.
Just a thought, but I would try laying the part on a surface plate and probing around with different thicknesses of feeler gage.
If the part moves during this probing I would put an indicator on the part above where your probing and see what's the thickest gage stock I can use before the indicator moves.
unrestrained does not mean you can't hold it with something, it (IMO) means you can't change the sharp of the part with what you are holding it with. Rough guess on the size of the thing is 0.75" x 0.825" (based on your image, with it being 0.018" thick), I would get a binder clip and hold it by the smallest possible edge, then using a probe that is almost parallel to the surface (not perpendicular) and measure a bunch of points and construct a plane and report the flatness.
depending on how big this is, i would build a fixture that has three points (one mounting point at each end and one in the middle where the bend is, apply some glue to the underside where the 3 points contact the part and measure the flatness.
BIGWIG7 Based on my assumption on the size (OP & sketch shows .018" thick so it can't be much larger that 1/2" squared) you would simply zero on the highest point on the top side of the part and look for the lowest point on the top side of the part. One could assume that could be done by simply changing the focus (our Starrett comparators will move almost 3" for adjusting the focus) to see the whole part
dwade How do take into account if the part is potato chip and you are only looking at it in one viewplane? You won't be able to see the "bow". I'm not trying to be difficult here I'm just trying to work out the best way to check this thing if I were in OP's shoes. *smooches*