Rex wrote:
woodworker88 wrote:

On Mar 6, 10:03 am, "T.Alan Kraus" wrote:

What is the usual finish for hydraulic master cylinders internal bores.
Say a brake master cylinder. Would reaming be good enough? Material
is 303

cheers
T.Alan


Usually they are honed with a Sunnen hone. Usually the point is to
remove any striations or rings (lines going either along the length of
the cylinder or around the bore).


Well, yes, but a certain fine finish is desirable, and a mirror finish
is not.

Yes I researched that and found out that there are two issues at play.
One is the obvious piston seal deterioration by friction with a rough
bore surface, the other is an increased stiction for the o ring seal
when the bore surface is too smooth. These two issues work against each
other and there is a happy medium. Somewhere I saw the figure of 20
micro inches or an Ra of 5. Can anyone confirm or shoot this down?

cheers
T.Alan