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  1. #1
    Silver Member indianaEPH's Avatar
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    Default What is wrong with this picture (connection problem)?

    I'm a bit stumped at why my hydraulic connections seem to be wrong. Here is the situation: I am trying to install a grapple on my tractor. I have the grapple it has a maile and female flat face skidsteer QD hydraulic interface. I purchased the QD set to mate with the grapple and also bought the tractor side hoses which will supply the hydraulic fluid from the rear remote.

    The problem I have is that when I screw on the QD to the hose connection it is a very loose fit. It does not tighten until the QD bottoms on the hose screw bolt shoulder.

    THe QD screw connection is 1/2" NPTF, the hose is list as a 1/2" Pipe thread.

    When I talked to the "expert" at Rural King he said that the 2 should work together and it will not be tight until you add teflon tape. I don't buy it.

    What am I missing?
    Attached Thumbnails Attached Thumbnails -img_0228-jpg   -img_0227-jpg   -img_0226-jpg  

  2. #2
    Super Star Member J_J's Avatar
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    Power-Trac 1445, KUBOTA B-9200HST

    Default Re: What is wrong with this picture (connection problem)?

    Perhaps someone has used it before to test something and put it back on the shelf. Npt is not designed for repeated uses, as the threads are compressed each time, and you should use paste or tape.
    J.J.

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    Git er done.

  3. #3
    Silver Member indianaEPH's Avatar
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    Default Re: What is wrong with this picture (connection problem)?

    Quote Originally Posted by J_J View Post
    Perhaps someone has used it before to test something and put it back on the shelf. Npt is not designed for repeated uses, as the threads are compressed each time, and you should use paste or tape.
    JJ, thanks for the reply. When I noticed the issue at home I went back to Rural King to see if the parts on the shelf did the same thing. They were the same

    The other connectors to the rear remotes are tight and as I would expect with NPT fitting.I'm now wondering if it is a NPT vs. NTPF issue?

  4. #4
    Platinum Member
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    Default Re: What is wrong with this picture (connection problem)?

    Here's a description of the difference, NPT Vs. NPTF Taper Pipe Threads , Long story short, the nptf thread seals by deformation of the creast of the thread. It's the same pitch and taper as npt.
    It shouldn't bottom out on the shoulder, either the male is cut undersize or the female is cut over......Mike

  5. #5
    Advertiser kennyd's Avatar
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    John Deere 4110, 455

    Default Re: What is wrong with this picture (connection problem)?

    Can you please post a picture of the two fittings NOT connected? I suspect one may be JIC rather than NPT.
    KennyD
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  6. #6
    Silver Member indianaEPH's Avatar
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    Default Re: What is wrong with this picture (connection problem)?

    Quote Originally Posted by kennyd View Post
    Can you please post a picture of the two fittings NOT connected? I suspect one may be JIC rather than NPT.
    Here are the pictures. THe packages are clearly labeled NPT and NPTF. Also, the same items in the store have the same loose fit.
    Attached Thumbnails Attached Thumbnails -img_0232-jpg   -img_0231-jpg   -img_0230-jpg   -img_0229-jpg  

  7. #7
    Platinum Member
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    Kuborta B2400, L2900, L4330; Caterpillar D3B, John Deere 455D

    Default Re: What is wrong with this picture (connection problem)?

    The hose is 1/2 NPT male "swivel", which is a straight mechanical thread rather than a tapered thread.

    NPT swivel fittings are like JIC fittings in that the connecting surfaces are male and female flares.

    You need an adapter or hoses with i/2 NPT male without the swivel modifier.

  8. #8
    Super Star Member LD1's Avatar
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    Default Re: What is wrong with this picture (connection problem)?

    I think the problem is the hose. I just dont see any taper to it????

    If it is lableld NPT that stands for

    National
    Pipe
    Taper

    NOT

    National
    Pipe
    Thread

    as many think.

    I think what you have is a male NPSM fitting on that hose

    Which stands for

    National
    Pipe
    Straight
    Mechanical

    There are only two ways those fittings work. Either in conjunction with a female NPSM fitting, which the females ALSO work with NPTF fittings

    or if used with an o-ring like an o-ring fitting.

    If I am correct that those are straight threads, I doubt thread sealer is going to work, and if so, not for very long.
    ".........there is only one way to find out."
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  9. #9
    Platinum Member
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    Default Re: What is wrong with this picture (connection problem)?

    LD1 is right: the correct name of the fitting on the end of the hose is a National Pipe Straight Mechanical thread (NPSM). The "mechanical" means that the thread is designed for the mechanical work of holding two fittings together, and not for sealing the join between the two fittings (as in the case of National Pipe Taper (NPT) or National Pipe Taper Fuel (NPTF).

    But I am fairly certain that the NPSM (male) fittings on the hose will not provide a seal against hydraulic fluid (or any other liquid) if connected to a NPSM (female) fitting; since neither thread is tapered, the male and female threads will have about the same clearance between them as a standard hex bolt and nut even when screwed together as far as they will go.

    But the NPSM (male) fittings on the hose are not mistakes; they are part of the common agricultural/construction hydraulic fitting class known as "pipe swivel." The male fitting, like the hose, has a 30 degree chamfer in the end of the fitting. The female fitting has a matching 30 degree cone which is pulled into the chamfer by a swivel nut on the female fitting.

    Other than the thread sizes and degree of flare, these fittings are similar (but not interchangeable with) the JIC flare fittings (37 deg flare) and SAE flare fittings (45 deg flare). Note that in the JIC and SAE fittings the swivel nut is on the chamfer or female flare end, and in the pipe swivel fittings the swivel nut is on the cone or male flare end.

    So, the original poster needs to obtain hoses with a true National Pipe Taper (male) fitting to match the National Pipe Taper (female) ports on his QD's. The packaging of his hoses is misleading: is describes the fittings as NPT Swivel when it should have said simply Pipe Swivel or more descriptively NPSM Swivel.

  10. #10
    Super Star Member LD1's Avatar
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    Default Re: What is wrong with this picture (connection problem)?

    Quote Originally Posted by Farmerford View Post
    But I am fairly certain that the NPSM (male) fittings on the hose will not provide a seal against hydraulic fluid (or any other liquid) if connected to a NPSM (female) fitting; since neither thread is tapered, the male and female threads will have about the same clearance between them as a standard hex bolt and nut even when screwed together as far as they will go.

    But the NPSM (male) fittings on the hose are not mistakes; they are part of the common agricultural/construction hydraulic fitting class known as "pipe swivel." The male fitting, like the hose, has a 30 degree chamfer in the end of the fitting. The female fitting has a matching 30 degree cone which is pulled into the chamfer by a swivel nut on the female fitting.
    A NPSM female and NPSM Male WILL seal when used together.

    What you are refering to that I highlited in red IS a NPSM female swivel fitting.

    Those female fittings that have that 30 degree cone in them will work with EITHER NPSM or NPSM fittings.

    The threads do NO sealing. It seals like a JIC flare fitting. Only the flare is inverted.

    So to simplify, we agree that he has a hose that has NPSM male threads

    You dont think it will work with a NPSM Female fitting. But your description of what that hose DOES work with (in red) IS a NPSM Female fitting. So they will work together.

    You are correct, the OP needs to buy a hose that is ACTUALLY a NPTF male end and NOT a NPSM Male.
    ".........there is only one way to find out."
    "Ok, hold my beer and watch this.........."


    Ford 5500 Backhoe
    Kubota L3400GST W/LA463 FEL
    2005 Dodge 3500 4x4 Diesel
    8N Rebuilt and restored
    Bushhog 306
    3 Homemade wood hauling trailers
    Dolmar 6400 84cc ported
    Sachs-Dolmar 120SI Ported
    (4) Sachs-Dolmar 116SI Ported
    Dolmar PS540
    Sachs-Dolmar 115i
    Sachs-Dolmar 117
    Sachs-Dolmar 112

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