Tapping a gauge...
Well first off you need to drill a hole slightly smaller than the gauge and or blowgun and and get a tap the size of the treads on the gauge and or blow gun. Tap the hole that you made so that the gauge and or blowgun will tread in to the hole. Always use tethlon on the treads of the gauge and or blowgun this will make it easier to just twist the gauge and or blowgun in just don't tighten them down to much, remember you don't want to strip your newly threaded hole. Good luck hope this help you
The term "tap" means to make female threads.
Last edited by sgort87 on Tue May 01, 2007 2:35 pm, edited 1 time in total.
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jimmy101
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You can usually "tap" the threads for the gauge without actually having a tap. Taps (the tool that cuts threads in a predrilled hole) are kind of expensive.
PCV (and ABS) is pretty soft stuff. Take a hunk of scrap and drill various size holes in it that are a bit smaller than what the gauge (or blowgun) needs. Carefully try to thread the gauge (or blowgun) into the hole. It is important that you start out nice and square to the hole. If you can't get the threads to catch in the hole then the hole is too small. If the threads catch in the hole very easily then your hole is probably too big.
Once you can get it to work on a piece of scrap then you can drill the same size hole in your gun and do it for real. If you are working with something that is fragile, many pressure gauges are pretty fragile, then see if you can find a pipe with the same threads. Use that piece of pipe as your tap to create the threads. Once you have the threads then your expensive / fragile device can be threaded into the hole without putting too much torque on it.
To test your "ghetto" tap job grab the gauge (or blowgun) and pull hard. Can you pull the gauge (or blowgun) out of the hole? You should not be able to. It is a good mental exercise to calculate how much force the gauge (or blowgun) threads will need to withstand. The force the threads have to withstand is just the area of the whole (in square inches) times the maximum pressure the chamber will be used at. For a combustion gun figure 80 PSIG maximum pressure in the chamber. For a compressed air gun figure 150 PSIG max. (If you have access to a kick-ass compressor then multiply the compressors peak pressure by say 1.5 and use that as the max pressure.) For example, a 1/2" diameter hole in a compressed air gun charged from a 120 PSIG max pressure compressor needs to withstand pi*(1/2/2)<sup>2</sup>*120 = 24 pounds of force.
Like ArticWolf said, don't over tighten your gauge (or blowgun). PVC is soft and you'll rip your nice new threads right out of the hole.
PCV (and ABS) is pretty soft stuff. Take a hunk of scrap and drill various size holes in it that are a bit smaller than what the gauge (or blowgun) needs. Carefully try to thread the gauge (or blowgun) into the hole. It is important that you start out nice and square to the hole. If you can't get the threads to catch in the hole then the hole is too small. If the threads catch in the hole very easily then your hole is probably too big.
Once you can get it to work on a piece of scrap then you can drill the same size hole in your gun and do it for real. If you are working with something that is fragile, many pressure gauges are pretty fragile, then see if you can find a pipe with the same threads. Use that piece of pipe as your tap to create the threads. Once you have the threads then your expensive / fragile device can be threaded into the hole without putting too much torque on it.
To test your "ghetto" tap job grab the gauge (or blowgun) and pull hard. Can you pull the gauge (or blowgun) out of the hole? You should not be able to. It is a good mental exercise to calculate how much force the gauge (or blowgun) threads will need to withstand. The force the threads have to withstand is just the area of the whole (in square inches) times the maximum pressure the chamber will be used at. For a combustion gun figure 80 PSIG maximum pressure in the chamber. For a compressed air gun figure 150 PSIG max. (If you have access to a kick-ass compressor then multiply the compressors peak pressure by say 1.5 and use that as the max pressure.) For example, a 1/2" diameter hole in a compressed air gun charged from a 120 PSIG max pressure compressor needs to withstand pi*(1/2/2)<sup>2</sup>*120 = 24 pounds of force.
Like ArticWolf said, don't over tighten your gauge (or blowgun). PVC is soft and you'll rip your nice new threads right out of the hole.
so that means I have to drill normally but with a hole slightly smaller than the gauge right?
wat mm drill bit should I use for a schrader valve?6.3500 mm I hope that is right if that don't work this will help. You can try this if you can get them it is a bolt in valve stem like in the pic. This could be mounted any were the bottom of it is wide so should work any were
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- bolt in valve stem
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Any auto part store, they should have them. Auto Zone and the like carry the but you might have to ask about them if you can't find them they should be around they reguler valve stem's But they are called A bolt in tire valve lol
A bolt? haha I'll try to find 1.. Where I live(Singapore) there's no Auto Zone.Thanks loads though... 
You drill a hole and they bolt in pic's might help
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- This is the top were the nut tightens it down
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- This is the bottom of tire valve
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frankrede
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DWV!ArticWolf wrote:6.3500 mm I hope that is right if that don't work this will help. You can try this if you can get them it is a bolt in valve stem like in the pic. This could be mounted any were the bottom of it is wide so should work any were
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