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question

Posted: Sat Sep 22, 2007 2:41 am
by watto
Hi
Should the part of the barrel that contacts the piston be sharp or completely flat.
thanks

Posted: Sat Sep 22, 2007 2:44 am
by jackssmirkingrevenge
Sharp will dig into your seal like a cookie cutter. Completely flat will do the same. What you want is to cut it at an exact right angle then bevel the edges slightly with light sandpaper.

In short:

> - bad

] - bad

) - good

Posted: Sat Sep 22, 2007 3:26 am
by Novacastrian
Just how my barrel is for my incomplete pneumatic :D

Posted: Sat Sep 22, 2007 5:07 am
by jackssmirkingrevenge
Novacastrian wrote:Just how my barrel is for my incomplete pneumatic :D
...which we would really like to see finished *hint hint nudge nudge* :D

Posted: Sat Sep 22, 2007 3:53 pm
by psycix
jackssmirkingrevenge wrote:Sharp will dig into your seal like a cookie cutter. Completely flat will do the same. What you want is to cut it at an exact right angle then bevel the edges slightly with light sandpaper.

In short:

> - bad

] - bad

) - good
thanks for this information :)
I was always wondering it but not asking since I am not building a pneumatic yet.

Posted: Sat Sep 22, 2007 11:21 pm
by meatballs
you want it to make good sealing contact so it dosn't leak, which is easier with a more pointed edge, but you want to avoid cutting through the sealing face. so i would change that analysis slightly:

> - bad

] - fine, but not the best. can work fine.

) - ideal