A quick question on total runout

[MacomMech]

My question is this:

If I specify a total runout of 0.05mm on an OD of 6.05 +/-0.05mm, does that mean when it gets inspected by QA the maximum allowable diameter is 6.15mm or 6.1?

 

[TheTick]

It sounds like runout is not what you need here. Sounds like a cylindricity requirement.

 

[TheTick]

Went to check my books. Judging from your last description, it sounds like cylindricity is what you need.

Here's an example: You have a shaft of Ø10 ±0.5. You need outer surface to vary only within 0.1 band, but the size tolerance is larger. Applying a cylindricity of 0.1 would accomplish this. Your size tolerance is large, but the amount of variation along the entire length of your cylinder is restricted, i.e. you could allow variance of Ø9.7 to Ø9.9 or Ø10.3 to Ø10.5, but you could not allow variance larger, like Ø9.7 to Ø10.3.

In application, cylindricity is a little more involved, but it accomplishes your goal. You may still be able to use runout in a similar fashion, but keep in mind that there are differences.

 

[Xplicator]

Cylindricity could work, but on your latest comment on the ideal size and tolerance. It sounds to me like you may have to look for a new tubing supplier? Perhaps a higher grade precision seamless and possibly a different material as well.

Hope this helps.

 

[MacomMech]

The Tick's final post is what I'm trying to do. (Sorry I'm new to this forum and haven't worked out how to quote yet) I chose TR over cylindricity because that might be easier to inspect given a suitable measurement jig.

I'm off to buy a GD&T book....

 

[ringman]

MacomMech,

I have some slightly used GD and T books for sale. Reasonable. Is there a way we could hook up?

 

[MacomMech]

May be moving back to the old tube supplier, currently getting a 30% failure rate on the part, used to be 2% or less. The tube is bespoke in Aluminium Oxide 96 ceramic.

Ringman where are you based, I'm in sunny Glasgow UK.

 

[KENAT]

MacomMech - what drawing standards are you using.

I can't remember if this is one of the areas ISO (hence British Standards) differ from ASME Y14.5 but seeing rule #1 referenced made me think.

I believe most of the above posters work to the ASME specs.

KENAT, probably the least qualified checker you'll ever meet...