Al Good ol' LBSC used to recommend - instruct - that pistons should be half screwed onto the piston rod. The other half should be a tight push fit, the reduced size being the same as the OD of the thread. The screwed part was at the outer end, of course! That way concentricity and security was assured. Regards Dave Saudi-Arabia-On-Sea --- Allen Messer <al_messer@xxxxxxxxx> wrote: > Harry, I must confess to threading the piston rod the full length of the > piston plus the height > of the nut. If this is improper practice, what diameter shoulder should be > allowed for the piston > to butt against? And I do agree that the piston should be finish turned on > its own individual > rod. ___________________________________________________________ To help you stay safe and secure online, we've developed the all new Yahoo! Security Centre. http://uk.security.yahoo.com MODEL ENGINEERING DISCUSSION LIST. To UNSUBSCRIBE from this list, send a blank email to, modeleng-request@xxxxxxxxxxxxx with the word "unsubscribe" in the subject line.