At 08:11 AM 2/19/06 -0800, you wrote: >#1--What materials were used in full sized practice and WHY cannot the same material be used in our models? Al, Not applicable. I've never heard of a full size loco with an axle pump, only crosshead pumps. Besides, there are conditions where the materal used in full size will work well on a model, and places where it won't. >#2--WHY must the inside of a pump bore be lapped It's not that it's a "must", but the smoother the bore the longer the O-rings will go between needing replacement, or so I believe. Now is the time to do it, before it's time to cut the chucking piece off the pump body. Regards, Harry 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.