CTF (Critical To Function) indication for a dimension 1

[freerangequark]

Our company's notes include the following:

There is some debate in our group as to whether the racetrack symbol should be simply a symbol placed in front of the dimension/tolerance, or whether the dimension/tolerance should be encircled by the CTF racetrack.

Is one way right and the other wrong? Is this ambiguous?

Is there a ASME Y14.5 standard for use of the racetrack symbol or for CTF dimensions in general?

Thanks!
Glenn

 

[lucky-guesser]

I have zero evidence to back this up but I'm fairly certain it is supposed to enclose the dimension. At least that's how I've always seen it done.

 

[Garland23]

I don't think there's any standard for how those symbols are to be used -- that's somewhat of a gaping hole considering that everything else seems to be defined (overdefined?) by industry standards these days. Therefore, each company that uses those symbols should have a note on the drawing or an internal company standard that addresses it (as the notes you give are showing).
That said, whenever I've seen the oval used for "critical" or Cpk purposes, the number has always been enclosed inside it.

 

[CWB1]

There is no correct method nor applicable standard bc you're using the print for something its not intended while trying to do somebody else's job. I'd recommend deleting those notes, they're a big red flag for any suppliers or customers who see them.

 

[3DDave]

It's an indicator of a Key Product (or Process) Characteristic - KPC. All the rage for some companies.

https://www.nist.gov/system/files/documents/2018/04/10/4mq7_brown_optimizingmbi_mbpc.pdf

for example.