After cutting a few dives short, some very uncomfortable deco stops and some near misses I decided it was time to get a P valve.
Now I could have just gone out and brought one but that would in no way help justify the purchase of my lathe/mill. So after a bit of research I found a design that was easy to make and proceeded with it.
Its a basic design that many have used before. The main body is made out of Acetal ( Delrin/POM) as is the external nut. There is a stainless steel bolt with a O ring that provides the opening and closing of the valve. A hose runs from the condom to the brass barbed fitting on the P valve body.
I have never cut threads on a lathe before so this was a bit of a learning experience. I needed a external thread on the main body and an internal one on the nut that clamps the valve to the suit. The other internal thread for the stainless bolt I cut with a tap.
The whole valve is quite compact and weighs about 80 grams, 35mm high and 40mm round.
I decided on an unbalanced valve as I can easily adapt it to balanced if I have any issues with it being non balanced and also unbalanced is also more reliable.
