JIC Hydraulic Fittings Problems - Practical Machinist

I've been making custom small hydraulic jacks. The way all the fittings are connected to the portapower is through a manifolds and rigid flarable-stainless tubing (0.250").

I've been flaring the ends (37 degree) and assembling the systems, but I still get light weeping in half the fittings at connection. Is this normal to have this many problematic fittings? Any suggestion on a different fitting series?

BTW, the system has static pressure, and it gets disconnected from the portapower. So it needs to hold pressure (psi) almost perfectly. The flare is the likely problem. Any quality JIC fitting usually seals like a dream.

Imperial tool with roller cone, 37 degrees, flare not too big to enter nut but enough for collar to grip. (If you have the correct Imperial tool the flare size can be preset before flaring).

Excuse me asking a dumb question but you do not say how much experience you have with JIC flares. You are using the proper nut and collar with your tube?

Brian I dont' have much experience at all with JIC fittings. All the fittings, collars and nuts are from the same 37 degree series (according to McMaster).

My Emperial kit has both 45 and 37 degree cones, I've been using the 37 degree cone. I think my problem is that I was having the tubing stick out too far, and it wasn't seated against the jaws at all while flaring, so it was making a flare in open space. I did a couple of flares where the material gets compressed against the jaw, it seems to make a more uniform flare. I guess I'll have to redo all my flares Applied,

Most of the tools for 37 deg flares do not seat on the jaws. This is a mistake that is made by careless people who do not read the directions. I do not know if you have the directions or not but I caution you as I have seen this happen more than once. The tube must stick out of the jaws a set distance, usually this is determined by a stop on the tool. Before you risk damaging your tool please reveiw the directions. I have used the emperial tools before and have never had any trouble with the flares if you follow the directions.

Please let us know what you find out, every tool is a little different.

Charles CBlaire,

Sort of one of the reasons I'm asking is because I've read the instruction that were given many times, and I still dont' get it.

They say that tubing + 1/4" stick out 1/16", but the for 1/4" and under the jaws have a counterbore, and they say it's recessed into the counterbore for proper positioning (in tubing under 1/4"). There's not stop on this tool. I think you guys may be talking about 2 different imperial flaring kits. I will use McMaster carr page numbers to illustrate. I have experience with both.

Catalog 112
1: Page illustrations B & K
2: Page illustration M

The first one is similar to every 45 degree tool you have seen. The cone pushes the tube against the female cross bar. My experience is that this works but can be problematic with hi pressure leaks.

The second one is the one referred to as having the tube stick out a certain distance. It uses the roller cone and the tube does not rest against the cross bar. While more expensive it does work really well and would solve any questions about sealing. It also takes less physical effort to flare the tube. This is one I now use for everything. Works pretty slick.

I may have missed it but be sure you are using 37 degree flared fittings. If you haven't split the tubing yet when flaring then you must have tubing that is not too hard. This is a good thing. Hard SS tubing tends to split when flared.

Hope this helps

Southeastern, ILGoing to order some hyd hose. I don't know how to tell what size the fitting is. I know they do the fittings in numbers. My JIC female end takes a 7/8 wrench. The threads inside are .672. TIA


Eastern NebraskaTHey are the same thread as fine threaded bolt I believe Maybe this chart will help



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Lawton, MI7/8 wrench probably a number 8 or standard size for 1/2" hose

Edited by andyn269 2/1/ 18:11




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Dills, FLhttps://www.hydraulicsdirect.com/Fitting-Thread-Chart-s/.htmGates has a really nice set of templates for all types of fittings and hoses.


Central NEAfter working around them for awhile, you'll be able to size them by eye, like a bolt. Use a open end wrench to size and then use the other posters chart.

ETA... slip open end wrench over the male threads, to size.

Edited by gemarsh 2/1/ 19:01
if they're not totally corroded you can usually see the number on one of the flats of the female fittingNtIf it's on a 3/8 hose it would be an 06-08. On a 1/2 hose it's an 08-08 fitting. Easy way to remember it's in 1/16ths. 08 is 1/2". Deere uses some 05 fittings on fuel lines. 10 or 5/8 is less common. Some on axial flow combines. 06 and 08 jic are the most used and go back and forth on 3/8 or 1/2 hose. Stock both hose size ends.

Galena ILNice chart

Wallis, TX - 2/1/ 20:55

If it's on a 3/8 hose it would be an 06-08. On a 1/2 hose it's an 08-08 fitting. Easy way to remember it's in 1/16ths. 08 is 1/2". Deere uses some 05 fittings on fuel lines. 10 or 5/8 is less common. Some on axial flow combines. 06 and 08 jic are the most used and go back and forth on 3/8 or 1/2 hose. Stock both hose size ends.

There are jump sizes, using just the hose size will get you the wrong end about 20% of the time.twraska - 2/1/ 20:20

- 2/1/ 20:55

If it's on a 3/8 hose it would be an 06-08. On a 1/2 hose it's an 08-08 fitting. Easy way to remember it's in 1/16ths. 08 is 1/2". Deere uses some 05 fittings on fuel lines. 10 or 5/8 is less common. Some on axial flow combines. 06 and 08 jic are the most used and go back and forth on 3/8 or 1/2 hose. Stock both hose size ends.

There are jump sizes, using just the hose size will get you the wrong end about 20% of the time.

If you follow my post I'm referring the op original fitting question. He had an 08 size fitting. Unknown whether it's on a 3/8 hose or 1/2. I'm giving him ammo so he knows what size he has.

Central IllinoisUse an open end wrench to quickly size the male thread. Wrench size is not always consistent on the swivel nut. There are standard and Heavy gauge swivels that take different size wrenches,

NW WashingtonThe tube fitting size number is the number of 1/16" of the tube or fitting. That is a number 4 is 4*1/16 or 4/16 which is 1/4" and so forth, a number 8 is 1/2" a 16 is one inch.dtracy
Posted 2/2/ 11:25 (# - in reply to #)
Subject: RE: How can you tell what size of JIC hyd fittings you have?...todd.crow
Posted 2/2/ 15:22 (# - in reply to #)
Subject: RE: How can you tell what size of JIC hyd fittings you have?


East Central MNSurplus Center has a really nice chart you can print out that is actual size to compare to the fittings .

http://www.surpluscenter.com/images/techhelp/JIC.pdftwraska
Posted 2/4/ 09:05 (# - in reply to #)
Subject: RE: How can you tell what size of JIC hyd fittings you have?