hey mate, if your after fittings, shraders, go to bridgestone tyre centers, 2 bucks each, (in aus, thats where i get mine. just go into the shop and ask for tubeless tire valves.) then drill a hole 12mm i think it is and then just pull the valve through, the base will seal itself in the metal. the metal cant be a centimeter thick though, if it is to thick, as for the metal motorbike valves. they are threaded, sorta look like this,
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there is a little rubber washer on the flat bit, and that seals your valve, and then just push it throgh a hole in your chamber and then put a bolt on the valve. worked for me.