Tuning Peek poppet lapping for seal

Jump to latest Follow Reply
Airgunmann

Airgunmann

Member
Jun 2, 2018
3,038
1,195
Minnesota, United States
What are you using to lap in your peek poppet to seal I have used some metal polish that had worked a couple times but this time I can't seem to get the poppet to seal all the way up I also tried a 30 degree and 35 degree taper just won't seal at 150 bar I now peek will seal all way down to like 500 psi I've had one do that for me please any suggestions for what to use to lap it into that valve Thanks 
 
  • Like
Reactions: monstr2
I had that problem on one of my valves and found that my valve stem clearance was a bit tight. After I took care of that it sealed just fine. Possibly I had a very slight angle on my stem but I just couldn't see it? Anyway after a tiny bit of polishing the inside of the valve where the stem rides was done it sealed up just fine.
 
  • Like
Reactions: monstr2
Upvote 0
You're on the right track. A concave face is as forgiving as you can get for a difficult material like PEEK. How confident are you that both the rim and its corresponding seat are free of tiny scratches? If unsure, color both parts with a Sharpie and apply a light abrasive like J-B (or a thick oil and diatomaceous earth slurry) and spin them together lightly for a few seconds. If the Sharpie marking isn't removed neatly on both the poppet and valve seat, the problem area should be clear.

Otherwise it's most likely as Biohazardman indicates, something is slightly out of square. The first PEEK poppet I ever made with caveman tools (drill press) was that way. To address it, I made a simple jig. It's just a 1-inch scrap of hardwood with a hole just big enough for the stem to pass through.
C8uR8U7.jpg
2B869CA3-5555-40F8-9025-611AB22ECDB6.jpeg


Then I used a hollow punch to knock out a bunch of holes in a piece of 220 grit sandpaper, which you see in the photo. From there, it's just a matter of putting the stem through the sandpaper and the wood block, and grabbing the stem from the back side with a drill and spinning it against the sandpaper to true it up. PEEK is tough as nails so it may take a while. Then a little time with 400 and 600 grit to smooth it.

Lastly, I lapped it to the valve with a light abrasive slurry using the Sharpie trick to gauge when I had done enough.

Naturally it's best if the hole you drill in the jig is perfectly perpendicular so do it on a drill press if possible, but even if it isn't perfect, it will still work. It will just make the poppet face slightly convex but still true to the stem.
 
Last edited:
  • Like
Reactions: monstr2
Upvote 0
I made the poppet on the lathe older atlas I have and tried seating or lapping it in with metal polish can see a slight black ring all the way around the poppet where it was spun in drill held to the poppet and the stem threw the hole last one I did sealed up right away almost now this one is being a pain I made the angle using the lathe the first one I just used a file while spinning with a drill so I don't know the angle would valve grinding compound work then lapped against the valve then use metal polish to clean it up farther I was holding onto the peek my stem is just press fit in 
 
Upvote 0
When I lapped my valve seal and seat I would often put the spring in, put the valve together and give it a little pressure before I chucked the stem in a drill a and spun it up. I did not notice the spring tearing this up inside so figured I was golden. I had one or two give me a hard time but I eventually prevailed. 

I have not used peek though always been Delrin.
 
Upvote 0
Derlin is easier to get a seal on found that peek can be a real pain some times lol . I may give his jig a try and see if that helps I got a few different steps in sand paper up to 1500 grit and Some metal polish to finish it out I'll drill a hole about same size as my valve throat or just undersized and sand it with a few different grits and see if that takes care of it hopefully it will not like it is a big leak but you can hear it with the barrel removed coming out transfer port


 
Upvote 0
What a coincidence. Today I was at a machine shop and I got my existing valve peek poppet re-cut to a smaller OD and I did myself polished a radius only on the lathe (R about 0.2-0.3 mm). I got home and put the Impact together (actually I have re-sealed everything what was on the table in bits and pieces). Air up the system and after some 2-3 hrs no leak yet. I am expecting when I start shooting the peek and the steel will match the seal.

Initially I did that power upgrade last year (peek poppet and larger porting in rear block and valve house), I polished high to shiny the metal valve seat only and the peek poppet was working out of machine...

Edit:

I found the pictures from exactly one year ago (I did not wanted to modify the original parts but I bought an extra set and re-machined those, when all was ready on the table I just replaced the parts). You can see the shiny surface in the upper valve housing? This all you need to do, the radius on the peek poppet will find a proper seat.

20201227_160847.1637554136.jpg

 
  • Like
Reactions: monstr2
Upvote 0
Makes me wonder if I don't have a oring leaking at the front of the valve it's a raw gun so if the oring leaks at the front of the valve it can travel up transfer port making you think it's the poppet I tried a different oring but wasn't sure it was the right size old oring I couldn't see anything wrong with it I'll have to double check that I guess to
 
Upvote 0
You must log in or register to reply here.
Top Bottom
Back
Home
Forums
Resources
Menu