Help drilling bronze

[Brian AbbottParticipant @brianabbott67793]

Hello all, need a bit of help and advice again,

I have been making myself a pm research water pump with the intention of using it to test my boiler when complete, put a gauge on it tonight to see how well it works, no problem upto 100 psi plus but will not hold pressure, drops down to about 30-40 psi.

Have tried taping the bearing down to get a better seat but does not improve things, am I expecting to much for it to hold the pressure, would I be better adding a stop valve?

thanks for any help.

[KWILParticipant @kwil]

You need a stop valve between the pump and your boiler, otherwise you are testing both together, whereas you just want to see if the boiler holds pressure!! 100 psi so the boiler working pressure will be 50?

[Nigel McBurney 1Participant @nigelmcburney1]

most of the drill problems with bronze (and brass) happen when a pilot hole is opened out or on drill breakthrough and on machines where there is no positive feed on the drill,or the work is not secured from lifting,i.e. drilling machine with work held by hand or in a light vice,or on a milling machine with hand fed quill.Where a controlled positive feed is used,i.e. lathe tailstock the drill will not spiral into the work ,unless the work is not tight enough in the chuck, jobs with long production runs are usually tooled and jigged to avoid such problems,its the short run or one offs that can lead to problems. Now some ask why bother to back off a drill,well a ordinary jobbers drill has a spiral which gives an approximate cutting rake of about 25 degrees, now they would turn or bore using a cutting tool with little or zero rake,yet feel that backing off a drill with a lot of cutting rake is not necessary.!!! During my apprenticeship and afterwards most of the work was in brass and bronze or cast iron and it was shop practise to back off a drill for these materials,it was a small company and I have often wondered why they did not have at least one set of backed off drills in addition to the conventional set to save regrinding when cutting steel and aluminium.

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