Print asking for Straightness of 0.013 and it has a note "Any Radial Element"

[jager]

I have a print asking for Straightness of 0.013 and it has this note "Any Radial Element". Can you tell me what that means? Does it mean straightness over the total part? It is a small washer. Thanks for any help.

 

[Jim Wynne]

Re: Straightness 0.13 Any Radial Element

I have a print asking for Straightness of 0.013 and it has this note "Any Radial Element". Can you tell me what that means? Does it mean straightness over the total part? It is a small washer. Thanks for any help.

I can't imagine what a straightness callout would do for a washer. If you could post the drawing (or a detail view from it) it might be helpful.

 

[jager]

Re: Straightness 0.13 Any Radial Element

I think they should have used Flatness instead. I don't think I can attach a drawing, but it is a washer with a 1 inch OD and in the ID are 4 equally spaced small radii and the part is about .030" thick. I hope that helps. Thank you

 

[Jim Wynne]

Re: Straightness 0.13 Any Radial Element

I think they should have used Flatness instead. I don't think I can attach a drawing, but it is a washer with a 1 inch OD and in the ID are 4 equally spaced small radii and the part is about .030" thick. I hope that helps. Thank you

It's common to see flatness/parallelism callouts for washers, but not straightness. You should talk to whomever it is that owns the drawing and make sure you understand what's intended.

 

[jager]

Re: Straightness 0.013 Any Radial Element

Thank you. I see a lot of prints with small errors and unclear notes. We'll check it out.
I appreciate your reply.

 

[David DeLong]

Re: Straightness 0.13 Any Radial Element

I agree that it should have been flatness but let's get back to your original question.

Straightness is a line or axis and is set up by 2 points at the ends of the line. If one has a drawing with a straightness feature control frame and stating "all radial elements", it means that one has to check in many locations from the centre (radial element) out to the circumference. The straightness tolerance applies to each element.

Please remember that the actual straightness is the worst condition found on any of the radial elements. Do NOT total them or combine readings.

 

[zancky]

Re: Straightness 0.13 Any Radial Element

my modest opinion:

it is right that flatness and parallelism callout are the most appropriate requirements for a washer but You may consider how to check it too.
Flatness may requires special device (very low flatness value can be check by glass light franges e.g. checking micrometer, common flatness values are inspected by CMM, etc).
Asking for Straightness seems to me your customer is requiring / suggesting a profile tracer as device (easy to use and easy to print out results)

by the way are you talking about 0.013 inch or mm?

 

[jager]

Re: Straightness 0.13 Any Radial Element

Thank you for the additional explanations. They are helpful and I do now understand radial elements. I would use the worse condition on my layout.

The spec is 0.013mm.

Thanks again.

 

[Stijloor]

Re: Straightness 0.13 Any Radial Element

It's common to see flatness/parallelism callouts for washers, but not straightness. You should talk to whomever it is that owns the drawing and make sure you understand what's intended.

Although not very common, I've seen straightness applied to surface elements and median/center planes of planar features.

Stijloor.