I’ve been reading that o rings can be easily damaged when putting together a gun. How do you take caution not to cut the o ring?
How to not damage an O-Ring during assembly
- Thread starter Pale_Rider
- Start date
Always lube o-rings before installing. They don't have to be dripping wet at all, just a very thin coat all over the o-ring. Make sure the parts where the o-ring seats are spotlessly clean with NO burr or sharp edges. Gently seat o-ring/parts together with the appropriate twisting or back and forth angle insertion as needed to give the o-ring the least chance of being pinched while properly seating it...
jmo
jmo
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ANY and ALL edges the o-ring must pass over needs to be chamfered / deburred. If you can slowly rotate the parts while assembling it will help the ring climb or get past possible catches that could nick it. Silicone grease on the rings is also suggested.
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1. Deburr and slightly radius/chamfer the holes with a rat-tail file, diamond ball burr, ball hone, etc
2. Apply silicone grease for assembly. Diver’s (SCUBA) grease or just automotive dielectric grease. For stubborn applications or things like a valve where it has to slide a long distance, lube both the O-ring and the tube. For example, my usual approach for installing a valve is to use a foam mop to apply a very thin film of silicone _oil_ (30W) to the tube and a little silicone grease on the valve O-ring and perimeter.
3. If the O-ring is still getting cut, use a blunt object to press down the O-ring while gently advancing it past whatever hole is cutting it.
And a couple of things that are obvious but are sometimes easy to take for granted:
4. Use the correct size O-ring. There are a lot of places where a dash size (imperial) can be used in place of a metric, and vice-versa…but sometimes the slight difference is just enough to make one more apt to getting cut.
5. Use the correct durometer. A high durometer (hard) O-ring is more likely to get cut on installation. 70 durometer is good for most AG applications if a particular durometer is not specified. 90 is good if you can get it installed. 50 is generally too soft for high pressure applications because it may extrude into the gap and fail.
2. Apply silicone grease for assembly. Diver’s (SCUBA) grease or just automotive dielectric grease. For stubborn applications or things like a valve where it has to slide a long distance, lube both the O-ring and the tube. For example, my usual approach for installing a valve is to use a foam mop to apply a very thin film of silicone _oil_ (30W) to the tube and a little silicone grease on the valve O-ring and perimeter.
3. If the O-ring is still getting cut, use a blunt object to press down the O-ring while gently advancing it past whatever hole is cutting it.
And a couple of things that are obvious but are sometimes easy to take for granted:
4. Use the correct size O-ring. There are a lot of places where a dash size (imperial) can be used in place of a metric, and vice-versa…but sometimes the slight difference is just enough to make one more apt to getting cut.
5. Use the correct durometer. A high durometer (hard) O-ring is more likely to get cut on installation. 70 durometer is good for most AG applications if a particular durometer is not specified. 90 is good if you can get it installed. 50 is generally too soft for high pressure applications because it may extrude into the gap and fail.
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As mentioned, pre-lubricating the o-rings is a must - to help them glide to/through where they need to go.
Another pointer is.. make sure that they're installed 'straight on'. level/plumb..
That way, their full circumference goes in all at the same time..
Very slight twisting or even a very small circular motion can also help..
Just don't install dry or slide them to/through at any sort of angle..
Also - If you feel as if there is any excessive resistance..
Back them out and try again.. Don't put too much force.. they can roll and/or be clipped/cut that way.
Sam -
Another pointer is.. make sure that they're installed 'straight on'. level/plumb..
That way, their full circumference goes in all at the same time..
Very slight twisting or even a very small circular motion can also help..
Just don't install dry or slide them to/through at any sort of angle..
Also - If you feel as if there is any excessive resistance..
Back them out and try again.. Don't put too much force.. they can roll and/or be clipped/cut that way.
Sam -
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No one mentioned O-Ring material. I switched to 90 durometer Urethane and I'll never go back to another formulation!
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While I do like D-urethane, and many other materials,, I find any o-ring material will pinch/cut/nick/leak if the basic above mentioned assembly tips are not followed. What I mean is no material is immune to nicks/pinches/cuts,,, its all in the precision of assembly and the preparation of parts...
jmo
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Polyurethane really shines in the area of tear and abrasion resistance. I used to be a proponent of it for general use but nowadays I only use it in places that are subject to abrasion (e.g. bolt / breech O-rings). Its tear resistance doesn’t translate so much into avoiding getting cut by a burr or pinched by a sharp edge.
For static O-rings—and that’s 90% of our uses—it doesn’t hold any particular advantages. For the most part, it’s just a more costly and harder-to-find alternative to Buna-N.
The other thing is its shelf life. Whereas Buna-N is 15 years, common polyurethane is only 5 years. The more costly cast polyurethane can be extended to 10 years.
But for a bolt O-ring? Yeah, polyurethane all the way.
For static O-rings—and that’s 90% of our uses—it doesn’t hold any particular advantages. For the most part, it’s just a more costly and harder-to-find alternative to Buna-N.
The other thing is its shelf life. Whereas Buna-N is 15 years, common polyurethane is only 5 years. The more costly cast polyurethane can be extended to 10 years.
But for a bolt O-ring? Yeah, polyurethane all the way.
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