Ive seen a few people use break and hydraulic line for air lines. I'd like to use some for an upcoming project. Does anyone know what OD diameter hard line fit into macro fittings?
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Should be 1/4" but I've never done this before so don't hold me to it.
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*brake. Not break.
Yes, 1/4" OD brake line will slide right on into a standard macro fitting.Comment
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304 Stainless tube will work with good quality Macroline fittings if you keep all of the bend out of the fitting (macroline fitting needs a good straight section to work especially with Stainless) Brass tubing works better and is easier to bend the little "teeth" bite into brass more. Make sure you bevel and debur your tube ends to keep from cutting the o-ring on insertion. Square edge of metal tubing will shear your o-ring with ease.
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Yup, 1/4 OD, I use 304 stainless with wall thickness of 0.049 ID 0.152 this has a rating of 6100psi @ 72F . Polish it up before you bend it by chucking into a drill with some scotch brite. This welded tube has markings printed on it. Tubing cutter works great.
Here is the link from McMaster-Carr where I source by 20ft and cut to desired length: https://www.mcmaster.com/8989K731/
McMaster-Carr part number - 8989K731
Not the easiest to bend but pressure rating is greater then anything we will expose it to. Use a good quality bender and I tape the ends after packing with fine table salt. This will help keeping from kinking on tighter bends and all you have to do is flush it out with hot fresh water when you are done. Do not exceed 1/2 inch bend radius. The general thumb rule when bending tubing is 2X OD for minimum bend radius.
oh, sometimes you have issues getting to seal consistently with metal tubing; all you need to do is pop out the o-ring and find one that is slightly thicker and pop it in.
Good old spit works for a lubricant when inserting the tubing into macro-line fittings, no need for anything fancy and your lubricant to evaporate once done the connection will be more stable. Air tool oil works and does not degrade the o-ring but can collect dirt and make it easier for the tube to pop out when you don't want it to [like when you are disassembling for another reason].Last edited by Grendel; 03-02-2022, 02:20 PM.
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Grendel any thoughts on brass tubing source? [asking for a friend
]
Velcor will save us...
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I get pretty much all of my metal from onlinemetals.com. They have a good selection of most everything. -
As Rusty Brass says online metals is a good source with reasonable prices. I've also bought from McMaster Carr (more expensive) and K&S Metals off Amazon in the past. Here is a link to McMaster Carr and as usual I tend to go overboard with pressure ratings even if it means harder to bend. I've been bending tube for 35+ years so not a big deal but bending tube well does have a steep learning curve especially when you are making tight bend in short lengths like we do for paintball. I tend to make the bend with a longer length of tube then I need then once the bend is done trim down the tube to fit. This is a lot more wasteful of tubing but helps avoid all the hassle of working with short tubing and screwing up the bend. Small tube cutter, ream and sand paper takes care of the ends/
https://www.mcmaster.com/tubing/material~brass/od~1-4/
Brass 260 tubing will work but is not technically pressure rated it is more of a structural brass tube [I found 1/4 inch OD tube has a nominal 870psi rating up to 200F and potentially all the way up to 3000psi but it is not tested under ASTM]. Even though McMaster Carr lists the pressure rated tubing as "Bendable - No" it will bend but is easy to kink so this is where you pack the tube with fine salt to act as a mandrel while bending (fine sugar works too) then you just soak and flush out with hot water.
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Will a quality macroline have enough grip to prevent the hardline from flying out when the marker is gassed up? Or does the hardline itself have enough rigidity to prevent 800+ psi from forcing itself out of the fitting?Comment
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First a caveat - the Macro Line fittings we use are not made or rated, in general, for the pressures we typically operate after the ASA and before a secondary regulator. That being said these fittings (metal ones) are hugely under rated because the industry application for them really does not need them to be better rated that is why they work most of the time for our uses in paintball.
Second caveat - Macro Line fittings are designed to work with actual macro line not for hard lines. I have fairly good results with using marcro line fittings with brass and stainless tubing but not 100%. Sometimes they do not hold into the fitting an leave little or no indication the "teeth" are gripping or they just leak especially if the tubing is moved. For leaking usually you can pull the o-ring and replace with a slightly "thicker" one and they seal up fine.
The fitting and the hard tubing is way stronger then the o-ring seal so when ever there is a failure it tends to just vent gas. I have never had a hardline become a projectile and due to how they are used and the required configurations (bends) I can not see any reason to worry about projectile tubing, given you are working on them depressurized to begin with. Once they are fully in place I have a hard time conceptualizing them getting loose to be a projectile.
...does the hardline itself have enough rigidity to prevent 800+ psi from forcing itself out of the fitting? Most definitely either brass or stainless steel tubing has a much higher rigidity then the "best" macro line you will find. It really is a moot point though since the sealing is done by the compression of an o-ring between the body of the fitting and the tubing so that really is the weakest point.
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If you want good safe and reliable air fittings and hardline tubing do not use Macro Line fittings. They are not made or designed for our applications so well be subject to problems. Below are a list of much better products for obtaining fittings that are appropriately designed and rated for paintball. [my favorite are Swagelok fittings]
https://products.swagelok.com/en/fit...c/154?clp=true
https://www.parker.com/portal/site/P...D&vgnextfmt=EN
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