Your experience of using o rings is totally opposite to that I experience. I
only use red or white silicone rings and they have quite a good stretch and
compression range. If a piston is a bit tight I simply skim the groove
deeper and lo and behold the fit is freer, its the same for piston rods
although I measure the od of the ring whilst it is on the rod and bore to
suit.
O rings are amazing if used correctly to suit our applications, remember
they are designed for super high pressures in hydraulics etc and the fits
need to be tighter, our fits need to be far less so need common sense
applied, which is where most who fail are failing.

----- Original Message -----
From: "John" <catboat15@...>
To: <halfinchlivesteamforum@...>
Sent: Wednesday, May 27, 2009 6:12 AM
Subject: [Half inch live steam forum] Re: O ring query


> Also remember the "rubber" or elastic material of an O ring is not
> compressable like convential packing. So the cut out for the ring must be
> wide enough to allow the ring to flex and expand out to the side as it is
> squeesed between piston and cylinder wall or shaft and gland.
>
> To me "O" rings were the greatest invention since mixing gin with bitters.