If you are experimenting with pneumatics being able to attach an airline or foot pump to your system is useful and to do so is easier if you can use a schrader type valve. In this instructable I will deal with making a standard rubber mushroom type valve stem as used on steel wheel rims into a screw fit valve stem.
you need either a rubber and brass valve stem as used on steel wheel rims which can often be had for the asking at any tyre depot that does a free valve and balance promotion as they cut the old ones off and bin them. If you have to buy a new one it's probably better to work out how to use it as designed rather than do this modification. If you happen to get hold of a solid brass (or sometimes alloy) stem as used on some lorry wheels or alloy car wheels you can skip the step about removing the rubber and go straight to the thread cutting.