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[skychair]

This may well be a really stupid Question, but
What does the 9/16 or 1/2 refer to when a brake line is 9/16-18, or 1/2-20?
Is it the nut size or diameter of the the threads?
I'm ready to do the Master Cylinder up grade, but the adapter I have BLF-26C will not screw into my Dorman M630031 master cylinder.
I dont understand...
Need some help/responses please.
Ron

 

[TigerEyz3]

First off, there are no stupid questions... we all learn something new at some point. Asking questions is often the quickest way to get answers.

Secondly, you're on the right track from a reading standpoint, but those numbers sound huge if you're talking about the actual brake line diameter, which is typically 3/16" or 1/4" for GM.

That said, the values you tossed out certainly sound like nut dimensions and thread counts:

• 9/16-18 is 9/16" with 18 threads per inch
• 1/2-20 is 1/2" with 20 threads per inch