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Valve mod - pcp pistol
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Pauly5 View Drop Down
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    Posted: 03 Sep 2024 at 9:41pm
After a long break from doing anything creative I have started on a new pistol build. This time I am making the valve differently. After some advice from fellow gunners and also copying a proven design I started.

Instead of trying to form a good seal on a surface within the valve body I am making the valve seat out of stainless and it will sit in the body, but can be removed/replaced if needed. You will see in the photo an FX Bobcat valve stem and seat, and next to it my valve seat with O ring groove cut into it and the valve body behind.

Next stage is the valve stem with sealing surface.
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nunga View Drop Down
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what are you making the value out of?
2nd place HP springer - WFTF World Championships 2014
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Pauly5 View Drop Down
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Valve body out of aluminium, the seat made out of stainless and I will use stainless for the opposing valve pin seat too.

My plan is to make the pin out of a screw driver shaft and then use valve grinding paste to bed them in with each other.

That's the plan.

I could make the whole pin and seat out of stainless, but I wasn't sure how well it will handle being struck by the hammer, where the screwdriver shaft is hardened.
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Posts: 2282 		Post Options Post Options   Thanks (0) Thanks(0)   Quote kruzaroad Quote  Post ReplyReply Direct Link To This Post Posted: 04 Sep 2024 at 9:30am
Question, would chisel shaft be better?, as they are designed to take to be hit.
You puting a regulator on it?
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ooh looks interesting
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Pauly5 View Drop Down
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The pin is around 3 - 4mm dia, so while a chisel material is perfect, it's too big.
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xyon View Drop Down
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If you need to machine the valve then a steel than can be annealed and hardened is good.
I've a used Class 10.9 or was it 12.9 bolt as they are strong but still machinable with HSS tooling.
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nunga View Drop Down
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The screwdriver shaft is not hardened only the tips are hardened steel. and you would find it very difficult to machine the hardened steel anyway. you will need grind it.

If it was me doing it i would be looking into 316 stainless for the valve and bronze alloy or brass for the seat. I have both here if you want to play with that. I have 10 and 20mm round 316 bar here. can easily make what ever bronze alloy you want.

Just a thought.
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Pauly5 View Drop Down
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Thanks Xyon, that makes sense, I might go that way. I know I could use HSS drill shanks too, then use the relevant reamer for the hole. But I have no reamers at this stage.

Kruz, I would like to put a reg into it, but they cost about $70 to $80 Euro + delivery each. I should be able to fit one at a later date as the way I have made the body should provide a plenum.
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Pauly5 View Drop Down
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Posts: 1409 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Pauly5 Quote  Post ReplyReply Direct Link To This Post Posted: 04 Sep 2024 at 11:14am
Originally posted by nunga nunga wrote:

The screwdriver shaft is not hardened only the tips are hardened steel. and you would find it very difficult to machine the hardened steel anyway. you will need grind it.

If it was me doing it i would be looking into 316 stainless for the valve and bronze alloy or brass for the seat. I have both here if you want to play with that. I have 10 and 20mm round 316 bar here. can easily make what ever bronze alloy you want.

Just a thought.

Of course, hadn't thought of brass or bronze. That would make sense.

With the screw driver shaft I don't need to change the diameter at all. I just cut to length then harden it. Giving it a polish afterwards.
I have about 1% metallurgy knowledge, but heat to cherry red or non ferrous state and quench in oil.

I have some 8 and 10 mm 316 round bar, but might take you up on the bronze alloy. Would only need a few small pieces.
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