Design criteria for a Bar Straightness Gauge

[DerrickWayne]

I need to build a gauge to confirm the straightness of various diameters of 12' long bars, used in the manufacture of screw machine parts. As the "straightness" of the raw material has a direct relation to the run out of the parts being machined on a screw machine, I need to be able to verify straightness. I have not been able to find design criteria or specifications relating to this, having consulted typical Gauge standards.
I have a basic design, which should meet my needs but I need to confirm if will comply with a known standard. Do any members have information which could help me in this.
Your assistance is appreciated.
Thank you very much.

 

[randi]

It's difficult to assign a solution unless the inspection requirements and tolerances are known in advance. On a scew machine you could be making parts that are only a few inches long or several feet long. I am assuming the screw machine as a general lathe machine term. But today you alos have NC lathes whose specification requirements for finished parts may be toatlly different.Specification and tolerances for straightness, concentricity, ovalness etc. may be obtained from the bar stock manufacturer, or per the applicable ASTM spec. applicable for the raw material Bar Stock.

Anyway one time we were chacking some thinwall aluminum tubing, that had lengths from 15 to 20 ft long. We layed the tubes on two sets of rolling disc stands ( the kind that are used for static balacing of impellers, manually )at either end. This way we were able to check the straightness at several points with a dial indicator along the axis by rotating it. You could also check the the o.d. and i.d. at extreme positions ( ends) for concentricity or ovalness etc.