Cylindricity controlling multiple surfaces.

[KA24DERoadster]

Can you apply Cylindricity to multiple features? I have a piston that has grooves cut into it, making the OD of the part not a continues surface. I need to control the Cylindricity of the entire OD of the part so that it fits properly into its bore. How do I apply the Cylindricity so that it applies to all of the OD surfaces as a single unit? Is there a way to do this or will each segment be free to float independently from one another?

 

[Gilmiril]

Call it a "continuous feature". ASME Y14.5-2009 introduced a symbol for this ("CF" is a hex outline).

 

[powerhound]

An example is on page 29 of the standard

John Acosta, GDTP Senior Level
Manufacturing Engineering Tech
SSG, U.S. Army
Taji, Iraq OIF II

 

[KA24DERoadster]

Thank you for your help. The book shows the CF symbol placed after the dimension for the features. Is this the only proper placement for the symbol? Are there any alternative ways to apply the symbol to the features?

 

[powerhound]

Thta's how it's shown. Just do it like that. Is there a reason you want to do it otherwise?

John Acosta, GDTP Senior Level
Manufacturing Engineering Tech
SSG, U.S. Army
Taji, Iraq OIF II

 

[ewh]

I've placed it below the dimension, depending on space available. I have also checked drawings with the symbol placed before the dimension and not marked it wrong. The main concern is that it not be mis-interpreted.

"Know the rules well, so you can break them effectively."
-Dalai Lama XIV

 

[KA24DERoadster]

I was just wondering if there were other ways to attach it like you have with datum and feature control frames. Sometimes it may be crowded and there is not enough space to throw it on the end of a dimension. If the end of the dimension is the only correct place for it, then that is where I will always put it even if it is cramped.

 

[powerhound]

Oh, I thought he was asking about something more extreme like sticking it in a FCF or something.

John Acosta, GDTP Senior Level
Manufacturing Engineering Tech
SSG, U.S. Army
Taji, Iraq OIF II

 

[Gilmiril]

I'm sure there are other ways to call this out. Maybe a leader note pointing to one surface with the text, "4X SURFACES <CF>"? But even if that's acceptable, I think keeping it with the dimension would make it less likely to be missed.