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Valve mod - pcp pistol

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Pauly5 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Pauly5 Quote  Post ReplyReply Direct Link To This Post Posted: 09 Sep 2024 at 10:06pm
Well I tried cutting one of my donor screw drivers and it was hard. The hacksaw had trouble biting into it. It made a small nick, so I just put it in the vice and it snapped on the nick.

Doing pest control I was always up in ceilings and sparkies often forget stuff and they do like to have expensive screwdrivers which are decenyly hardened. So I have a couple I can wreck. So this will be my valve stem.


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RangerPete View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote RangerPete Quote  Post ReplyReply Direct Link To This Post Posted: 09 Sep 2024 at 11:08pm
Good luck with that 😂
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Pauly5 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Pauly5 Quote  Post ReplyReply Direct Link To This Post Posted: 18 Sep 2024 at 9:50pm
Slowly doing stuff.

NZ Post has botched up Nunga's foundry delivery, so valve on hold. I bought a piece of 3.9 mm piano wire today. Pretty hard, and hopefully harden up, but I might try that for the valve stem.

I also decided to use the .25 cal FX barrel I had. It was off a Bobcat. I cut it down and reduced the breech end to fit into what will be the breech block for this build. Fits nice and snug with no movement.

FX only rifled the last 2 or 3 inches of these barrels and you can see that they make the muzzle smaller diameter to do this, then thread on a piece to match. You can see the marks on the outside where they "squeeze" the rifling in giving it a "smooth" twist.




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Post Options Post Options   Thanks (0) Thanks(0)   Quote RangerPete Quote  Post ReplyReply Direct Link To This Post Posted: 19 Sep 2024 at 10:19pm
So how long are you planning on making the barrel?
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Pauly5 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Pauly5 Quote  Post ReplyReply Direct Link To This Post Posted: 19 Sep 2024 at 11:19pm
Barrel is around 300 mm, so not a small pistol.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote J-S Quote  Post ReplyReply Direct Link To This Post Posted: 20 Sep 2024 at 11:39am
very cool
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Pauly5 Quote  Post ReplyReply Direct Link To This Post Posted: 21 Sep 2024 at 11:46pm
So i found a piece of brass to use. I have made the poppet valve and loctited it to the stem.

After it was fastened I finished off the seat and polished it so the it was concentric with the shaft. I am quite pleased with how it turned out, but of course being pretty doesn't mean it works.

I also polished the valve seat. I have some of the 3M polishing cloths, 800 up to 15000 grit. It is satisfying working through them and seeing the finish improve.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote nunga Quote  Post ReplyReply Direct Link To This Post Posted: 22 Sep 2024 at 8:34am
Silly question, You are going to lap the seat in right? That brass looks nice but is it just the picture or are there a lot of machine marks still on the face of that? hope it seals.

Nice work! I will get the other brass sent out again for you anyway and you can use it on another project if you dont need it for this now.
2nd place HP springer - WFTF World Championships 2014



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Post Options Post Options   Thanks (0) Thanks(0)   Quote KiwiTR6 Quote  Post ReplyReply Direct Link To This Post Posted: 22 Sep 2024 at 8:36am
Paul, I've found Solvol Autosol to be excellent for final polishing.  I'm not sure if it would be coarse enough to finalise the metal to metal seal though.  I have heard of people using moistened cigarette ash on fuel needle jets, but that's probably finer again.
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Pauly5 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Pauly5 Quote  Post ReplyReply Direct Link To This Post Posted: 22 Sep 2024 at 8:49am
Thanks guys, yes I was going to use something to bed the two together. I have Autosol, valve grinding compound and even toothpaste.

Nunga, this is kind of a test run. I don't know how well this will work and so the good thing is that I can take the whole valve system out and replace it, so I will use your piece of brass because it was made for it. It means something to me to use the piece cast especially for it. I can make the mistakes on this first one.

The other thing I was going to do was make the seat out of delrin.
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