What about internal lubrication of PCPs???

[Vana2]

What about internal lubrication of PCPs???



I have read about people adding a drop of silicone oil to the fill probe (occasionally) of their PCPs to (lightly) lubricate the internal seals and parts of their rifles.



In view of recent posts about air leaks I wonder if a small amount of lubricant would be better than running the guns “dry”.



Any thoughts or comments on this?



Cheers!

Hank



By coincidence, a recent posting (28 Apr ’20) on the Pyramyd Air blog is about O-rings and mentions this. Below is a link and a couple of comments (paraphrased) that may be of interest…

https://www.pyramydair.com/blog/2020/04/a-little-about-o-rings/

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RidgeRunner

As you have noted, sometimes a little lubrication can help an o ring immensely. With most PCPs I like to put a couple of drops of silicone oil on occasion in the foster fitting when I fill them. This will enter the air reservoir and disperse throughout the air rifle, many times refreshing the sealing capabilities of o rings. If there happens to be a slight leak at a particular o ring, the silicone oil will migrate to there, lubricate the o ring and usually help seal the slight leak.



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Kevin

I’m fortunate to have one of the world’s largest distributors of o rings 15 minutes from my home. Rocket Seals carries AND MAKES all types of o rings:


Here are some of the things regarding lubrication of O-Rings that they told me that I remember:



1-never use petroleum based lubricants



2-silicone grease or silicone oil is preferred in most applications. Silicone grease stays in place and keeps the O-Ring in place better for assembly-reassembly but for lubing large amounts of o-rings silicone oil is ok. NEVER use silicone oil sprays since they typically contain petroleum based products as carriers. Quit using Vaseline.



3-Food grade silicone grease for many applications is paramount when contact with humans is expected, i.e., scuba diving regulators, medical breathing devices, food production, etc.



As to how much lubricant to apply use common sense. Are you reassembling a watch or are you a plumber putting together a 12″ connection? BTW, silicone grease is so common with plumbing it’s often called and labeled Plumbers Grease.

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Gene Salvino

Most important topic when repairing guns is sizing the seals. There are 2 sizes



- SAE which are #009 etc.



- METRIC which is ID and DIAMETER so a 7 x 2.5mm is 7mm on the ID and has a Diameter of 2.5mm



Keep in mind when repairing a gun with dried out seals sometimes they will look square! Measure the seats and OD to help match up. I would say on average a reseal will last about 5 years with Buna. The longevity of the seals is dependent upon the manufacturers keeping the tolerance tight so the seals will not extrude.



I have a Metric and SAE set at home also for tinkering, problem is the assortments miss allot of the needed sizes. They go off of AC and Air Tool sizes that are commonly encountered in automotive work. Not a bad kit for the money, my kit is older and seals are of US mfg., my friend bought the same kit recently to redo some air tools and they are Chinese seals! Watch out for the Harbor Freight kits, I have redone allot of customers guns from those soft seals! Source them from Grainger or McMaster save yourself some frustration and time.

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[elh0102]

I would not put a drop of anything in the fill probe. Silicone is okay for very lightly lubing O rings when assembling, but it needs to be kept well away from any metal-to-metal bearing surfaces that are under high pressure, as it can cause seizing. Internal lubrication needs vary with rifle design and materials. The only thing banging around in there is the hammer assembly, and the lubrication of that (if any) should be based on the maker's recommendation. It definitely needs to be clean, but some operate dry, others with light lubrication, at least that has been my experience. 

 

[Bigragu]

Correction on the comment regarding metric seals- 1st call out number is the I.D. Meaning Inside Dimension of the Diameter, which is correct as stated above, but the second number is NOT the diameter; it is the Sectional thickness of the O ring.

So in the example given above of 7mm x 2.5mm, it means it’s Inside Dimension of the diameter is 7mm, and the thickness of the O ring is 2.5mm. Some overseas companies like my recent experience with Tuxing when sourcing parts for my Lightning compressor, they gave me o ring sizes with the first number called out in O.D. Meaning outside dimension of the diameter. One must verify that if it is not stated anywhere what the first number means. Don’t assume it is the Inside Dimension.

So in the case of Tuxing, the example size given above using the 7mm x 2.5mm would’ve been 12mm x 2.5mm. That is, thickness x 2 + I.D.



Thats all I have to say about that. 



I keep telling myself to once in awhile to drizzle the fill probe o rings with silicone oil, for the reasons suggested above, but always forget to. I think I’ll be ok, though, cause I’m in and out of my guns often, so there’s always some type of lube in there.

 

[JWilson]

I believe the single most important aspect to maintain the internals of a properly assembled PCP is to feed it clean dry air.

Joe

 

[nervoustrig]

Silicone grease for static seals. Its high viscosity aids assembly and helps minimize the risk of damage during installation.

Silicone oil for dynamic seals. Generally the only place that applies in a typical PCP is the bolt or breech O-ring, and to a lesser extent the check valve O-ring. Otherwise it’s mostly for high pressure pumps.

As Edward said, avoid using silicone lubricants on metal-to-metal interfaces like the hammer. For that, either polished and lubricated with a light oil (almost water viscosity), or dry burnished with graphite, molybdenum disulfide, or tungsten disulfide. For trigger groups, I’ve tried lots of different lubricants and concoctions and have settled on a 50/50 mix of molybdenum disulfide powder and FP-10…at least until I try something else and decide I like it better. You can substitute 30W non-detergent oil for the FP-10 with similar results, just not quite as long-lasting.