Straightness Tolerance Box 1

[ImnotfromMars]

Hello,

Today I saw a tolerance box for straightness which had a tolerance of .005/1 RFS.

I guess it means the part must be straight within .005 per inch. Does anyone know where in the ASME Y14.5 it allows this? I was unable to find it.

 

[Belanger]

See paragraph 5.4.1.3 of the standard ASME Y14.5-2009. Also see Fig. 5-4, which shows that "per-unit" idea as a subset of an overall straightness tolerance (although the overall straightness isn't necessarily required).

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

 

[tbuelna]

Just a minor point, but that straightness tolerance likely applies to a specific surface or feature and not the entire part.

 

[ImnotfromMars]

Yes, Thank you.

 

[DanAbbott]

This type of unit restriction can also be used with flatness. I've never seen it by itself -- always as a composite control with an overall tolerance above and a smaller unit tolerance below.