Straightness of a cylinder.

[[Da...]]

Straightness. 2 definitions and a misinterpretation.

If the straightness callout is attached to the diameter size, then I would check several diameters along the cyl and recall those circles into a 3d line. Ask for straightness of the 3d line and it will produce the 3d variation of the centerlines of the circles. This would show if the cyl is bent.

If the straightness callout is attached to the surface of the cyl , then I would make a series of axial 2d lines along the surface of the cyl and ask for the max straightness of the group of 2d lines. This would show if the SURFACE of the cyl is straight. (but it will be influenced by whether or not the cyl is BENT).

At least one of our customers refers to straightness as the amount of allowable taper for the DIAMETER along the cyl. (I consider this a misinterpretation).

My current issue is involving a print marked as ASME Y14.5-1994

The straightness callout is for surface of a cyl in 3 separate sections. The tolerance is .0012 mm.
The part has been mfg since 2014. I'm wondering how this is being verified. Should I try single points?

[[Je...]]

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Based on your description, it sounds like your customer is confusing or convoluting Cylindricity with Straightness.

Additionally, based on your description of your work flow (which appears correct btw), have you taken the CALYPSO Expert course? A method is taught that allows a formula based approach to your cylinder measurement strategies and recalls. It allows you to utilize axial 2d lines only for both types of straightness requirement and gives a much more robust analysis of axis straightness. No circle scans needed.

[[sh...]]

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[[Ry...]]

https://jmp.sh/X72WubHh

Since Jeff mentioned Expert class... Attached is the output of the straightness of a cylinder axis derived from 5 linear scans on the cylinder. The attached is output from one of our student's labs.

🙂