O-ring sizes?

Joined: May 14th, 2004, 4:11 pm

September 21st, 2009, 3:38 pm #1

Does anyone know the oring sizes that fit around the valve and the fill adapter to seal against the inside of the air tube? They are parts #18D and 37B on the parts diagram, not the actual part #'s. The Crosman parts list does not mention the size. Also what would the best material and hardness?

Thanks
Jeff P
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Joined: September 21st, 2007, 12:13 pm

September 21st, 2009, 5:21 pm #2

those as O-RING, AS568-016 that would be the size. I just bought a bag of Mil Spec Viton fromhttp://www.mcmaster.com/
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Joined: May 14th, 2004, 4:11 pm

September 21st, 2009, 5:48 pm #3

I suppose the bolt orings are good at 90 durometer but seems these should be softer?

Jeff P
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Joined: September 1st, 2009, 8:19 am

September 21st, 2009, 7:11 pm #4

O-Rings are normally sold in dash sizes For example a valve o-ring might be a dash 016, 70 often written as -016/70 The second part of the number indicates the hardness. You really need both parts of the size to get a correct o-ring. As example a tank o-ring might be a -016/90. That o-ring will fit the valve that specs a -016/70 but it will not work correctly because it is too hard. On the other hand the -016/70 o-ring for the valve will fit the tank, but because its too soft it wont last long at all.

If we were talking about paintball guns, I could tell you the correct size/hardness o-ring for about any area of any gun, but I dont have that knowledge for pellet guns. NORMALY most parts lists will have the correct o-ring size in the part number (no sense in reinventing the wheel). So if I see a part number like UR-01670 I can make a good guess that its a urethane -016/70 o-ring. Sorry I can give you exact sizes for pellet guns.

Craig
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Joined: May 14th, 2004, 4:11 pm

September 21st, 2009, 8:15 pm #5

I knew that not only size but hardness was important. The Crosman part no. is AS568-016, so other than the 016 size it does not seem to reveal its hardness.

Jeff P
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Joined: September 21st, 2007, 12:13 pm

September 21st, 2009, 9:36 pm #6

I suppose the bolt orings are good at 90 durometer but seems these should be softer?

Jeff P
75D. I've found that with the harder 90's are less compliant, and require
much more force when installing the valve and gauge block. So even though I polish, and bevel the tube end,and use sil. grease, I feel that they might shave a bit when starting them into the tube. As far as the bolt o ring, I don't like the extra effort needed to seat a 90d ring on closing the bolt, and since this o ring is only under pressure for a fraction of a second, I don't see any gain in using a 90d over a 75d on the bolt.
Some folks have had problems with the bolt jumping on firing, and use a 90d ring to try to increase radial pressure on the bolt to help keep it from jumping open.
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Joined: September 5th, 2008, 1:33 am

September 23rd, 2009, 2:16 pm #7

when you say "75D", you are using "D" to stand for durometer, not the hardness scale.

Elastomer hardness is typically measured on either a "Shore A" or a "Shore D" scale. The "A" scale is 'softer' than the "D" scale. The two scales overlap.

A comparison of these scales can be found at:
http://www.machinist-materials.com/hardness.htm

Don't mean to nit-pick your post, but didn't want someone who wanted a 'soft' o-ring to order a "40D" hardness o-ring when they were really after a "40A" and end up a hard one similar to a "90A".

Other examples of hardness of different elastomers can be found at:
http://www.hapcoweb.com/GeneralPages/hard_chart.htm

Cheers,
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Joined: September 21st, 2007, 12:13 pm

September 23rd, 2009, 6:05 pm #8

my ref's are Shore A Dur. hardness scale.
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Joined: July 14th, 2008, 8:33 am

September 27th, 2009, 3:22 am #9

O-Rings are normally sold in dash sizes For example a valve o-ring might be a dash 016, 70 often written as -016/70 The second part of the number indicates the hardness. You really need both parts of the size to get a correct o-ring. As example a tank o-ring might be a -016/90. That o-ring will fit the valve that specs a -016/70 but it will not work correctly because it is too hard. On the other hand the -016/70 o-ring for the valve will fit the tank, but because its too soft it wont last long at all.

If we were talking about paintball guns, I could tell you the correct size/hardness o-ring for about any area of any gun, but I dont have that knowledge for pellet guns. NORMALY most parts lists will have the correct o-ring size in the part number (no sense in reinventing the wheel). So if I see a part number like UR-01670 I can make a good guess that its a urethane -016/70 o-ring. Sorry I can give you exact sizes for pellet guns.

Craig
any ideas what O-ring would fit a Nitro regulator for a 68 cu in paintball tank?

That's the one that seals the regulator to the tank.

TIA
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