A rough figure is to 'assume' the o ring is 0.0625 dia which it isn't, a
1/16" o ring is 0.070" section so you get a bit of nip. Basically I adjust
to suit what I'm making as I see fit.
A 0.25" hole with a 0.125"id ring would give a nice sliding fit on 1/8" rod,
if you make the hole slightly bigger the ring can expand a bit so the fit is
freer but could leak under high pressure, this is where the 'I see fit' bit
comes in, I have to apply a bit of practical knowledge of what I'm using the
ring for.
The limits & fits tables in the reeves book are quite good as a base line, I
can scan tonight if you like? Just off to work.
Simon.

----- Original Message -----
From: "david_steam" <no_reply@...>
To: <halfinchlivesteamforum@...>
Sent: Tuesday, May 26, 2009 8:53 AM
Subject: [Half inch live steam forum] O ring query


>I recall somewhere seeing a 'limits and fit' table for O rings?
>
> Assuming a 1/16" O ring, if I wanted an, ID of 0.25" what depth and
> diameter spotface cutting would I require?
>
> Again if the OD was the critical factor of 0.25" what would the ID have to
> be?