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All Springer/NP/PCP Air Gun Discussion General > Machine Shop Talk & AG Parts Machining

Machining port into aluminum airtube?

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Volvonium:
Howdy all, I was considering picking up a couple of aluminum air tubes from Travis @ JSAR for my Marauders/Armadas.  Aside from weight reduction and balance improvements, one thing that I did want that they do not currently include was a port for the valve metering adjustment screw when using the stock Mrod valve. 

I have also been considering relocating the gauge port to the side, rather than on the bottom (I want to make some custom stocks), so I was thinking of picking up a couple of his tubes without the gauge port.

My biggest concerns when drilling an aluminum air tube are safety and structural integrity, since these are on the high pressure side.  If this is a feasible thing to do, what process and finishing considerations would I have to bring to a machine shop so that they can drill out these ports in a safe manner that does not compromise the integrity of the tube? 

rsterne:
The velocity adjustment screw is behind the valve O-rings, so that part of the tube is NOT pressurized.... If you install a gauge block, likewise it has O-rings both sides of the hole for the gauge, so that area BECOMES unpressurized.... Just make sure you carefully deburr the gauge hole, particularly on the inside, otherwise it will shred the O-rings on installation....

Bob

Volvonium:
Damage to the o-rings is one thing I had in mind, the other was whether there was a realistic concern for things like microfractures developing around the drilled area after many cycles of the tube being pressurized and depressurized.  I'm overly cautious because high pressure rifles are still relatively new to me, but I suppose if the seals are operating as they should, there could be quite a lot of holes in that entire unpressurized area, akin to the unpressurized rear section of the tube where the hammer, spring, and sear are located. 

Thank you for the input, Bob!  I was overthinking the issue, but can never be too safe.

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