MetaRinka
Cast Iron
- Joined
- Jun 23, 2008
- Location
- Ann Arbor, MI
Help me out folks, I'm an engineer trying to get my set of numbers straight so I can sort out the issues with a manufacturing process. Long story short I was given a a table of numbers with circularity calculated but I don't think the inspectors methodology is right and I wasn't able to reproduce the results . Before I go throw sand in their face and tell them they did everything wrong and they are horrible people I want to make sure I understand this issue.
We have a rolled sheet metal cylinder called out at 15.000" on the I.D
The callout is for roundness within 0.030"
straightness within 0.015
The part was set on blocks and measurements taken in 6 places along the circumference. For straightness a straight edge was used and shim gauges used to find the area of lowest height along the longitudinal axis of the part. This was measured as straightness
Now for roundness the straightness measurements were used and the area of lowest height among the 6 areas it was clocked at was doubled and listed as roundness.
This feels wrong to me that would be taking measurements off the longitudinal axis of the part. My understanding is that circularity is the quality of every part on a circle to be equidistant to the center point. Therefore to measure roundness you would take Diameter readings at however many parts, and the Difference between the lowest and highest Diameter would be your circularity. we don't have anyway to spin this part right now precisely, so we're going with taking mic readings at 6 points (3 diameters)
We have gauges but apparently the parts are so far out the bore gauges and other tools for measuring inside diameters we had can't measure them (only go 0.010" or so)
so help out the clueless engineer.
Am I on the right track to calculating circularity?
We have a rolled sheet metal cylinder called out at 15.000" on the I.D
The callout is for roundness within 0.030"
straightness within 0.015
The part was set on blocks and measurements taken in 6 places along the circumference. For straightness a straight edge was used and shim gauges used to find the area of lowest height along the longitudinal axis of the part. This was measured as straightness
Now for roundness the straightness measurements were used and the area of lowest height among the 6 areas it was clocked at was doubled and listed as roundness.
This feels wrong to me that would be taking measurements off the longitudinal axis of the part. My understanding is that circularity is the quality of every part on a circle to be equidistant to the center point. Therefore to measure roundness you would take Diameter readings at however many parts, and the Difference between the lowest and highest Diameter would be your circularity. we don't have anyway to spin this part right now precisely, so we're going with taking mic readings at 6 points (3 diameters)
We have gauges but apparently the parts are so far out the bore gauges and other tools for measuring inside diameters we had can't measure them (only go 0.010" or so)
so help out the clueless engineer.
Am I on the right track to calculating circularity?