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NPT and NPTF threads

Posted by Flash, Apr 23, 2007
Bolt-on Tech - 4G63 intake, exhaust, intake manifold, ignition, fuel system, cooling, etc.

  1. Flash

    Flash Proven Member

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    I plan to get something that uses sensors that are 1/8 NPTF. And I am wondering if NPTF fittings would fit in a hole tapped for NPT. I read that basically NPTF will create a tighter more leak-proof seal, but I never saw anything about if NPTF is compatible with regular NPT.
    Example of my scenerio: I know the 2g oil filter housing has some taps for 1/8 NPT and the oil pressure sensor is 1/8 NPTF.
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  2. absolute_DSM

    absolute_DSM Proven Member

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    From what I know, since NPT threaded parts require some sort of sealing compound, you can use something threaded NPT in NPFT hole.
    You CANT use a NPFT sensor in a NPT hole because it will more than likely leak. The threads just arent tapped correctly for a NPFT sensor to seal by contact.

    Make sense?
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  3. Flash

    Flash Proven Member

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    So what's a suggestion for tapping a hole that already threaded for 1/8 NPT for a 1/8 NPTF sensor?
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  4. 99gst_racer

    99gst_racer Moderator

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    I was always under the impression that it was tapped for BPT (british pipe thread). All you have to do it chase it with an NPT tap and you're good to go.
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  5. Flash

    Flash Proven Member

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    So chasing the threads in the oil filter housing with like an NPTF tap, it will not screw up the threads?
    Thanks for the info!
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  6. Flash

    Flash Proven Member

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    Paul, I think you mean BSP. I was just reading the 80 page instruction manual that comes with this thing and it said that there is an option to get the 1/8" NPTF thread supplied with 1/8" BSP adapter. Seems a little easier.
    All sensors are NPTF, just can be supplied with adapters for either BSP or M10 x 1.
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  7. Flash

    Flash Proven Member

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    It comes with a fuel pressure sensor too and it's NPTF as well. What do I use? I was planning on running SS line with AN fittings, with a fitting that has a 1/8 NPT tap. I just dont want to screw the NPTF sensor in the fitting and have a fuel leak in the engine bay.
    Suggestions?
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  8. FORMONTOYA

    FORMONTOYA DSM Wiseman

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    The filter housing (or most sensor "pipe" threads on a DSM) is BSP threads.

    I believe you'll be hard pressed to find sensors with NPTF threads as they require more precision to form the threads correctly, especially when a little dab of sealer or tape will seal the joint which will not see a whole lot of pressure....100 or so PSI is NOT high pressure.

    Good luck to you though.



    A little something for those that don't know what NPTF threads are:
    http://www.cutting-tool-supply.com/TechTips/Tapping/NPTvsNPTF/NPTVsNPTF.htm
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  9. daren_p

    daren_p DSM Wiseman

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    From what I have read, it seems you can use NPTF in a NPT hole but you will now need to use a sealing compound. I don't think you can just run a NPTF tapp through the hole & expect it to seal without the use of any compounds. The larger plugs in the oil filter housing are BSP, I believe 3/8". I know when I did my oil pressure gauge I tried a 3/8 to 1/8 NPT adapter but didn't like the fit as it only turned in about 2 turns. I found a 3/8 BSP adapter but this needed to be screwed all the way in & sealed on an oring at the end of the fitting which I didn't feel confident about it not vibrating lose. So what I did was take a stock plug, drill it out & tapp it, screw in adapter that would accept my sensor thread size (think 1/8 NPT) & have the stock plug & adapter welded together. This way everything is a perfect fit & don't have to worry about leaks or anything coming lose.
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  10. Flash

    Flash Proven Member

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    Thanks for the help Daren. This is just really confusing me. This gauge comes with sensors that are all NPTF for coolant and oil temp, then fuel and oil pressure. It confuses me how I am going to make this work.
    http://www.42draftdesigns.com/product/vdo/42921.htm

    Suggestions on how to make the fuel pressure sensor work?
    #10
  11. absolute_DSM

    absolute_DSM Proven Member

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    I believe its the other way around Daren.

    Correct me if Im wrong, but when they say you can use the tap for an application, they are saying the hole would be threaded (tapped) NPTF and a NPT sensor could be used in it.

    Im not doubting that you could use a NPTF sensor in a NPT with some sealing compound, as stated before, 100psi is NOT a high pressure situation.
    #11
  12. Flash

    Flash Proven Member

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    Ok, well I decided to research further on the compatibility of NPT and NPTF fittings tonight. Honestly, there is hardly any info around with this type of info as it pertains to cars. The link I found says: "Male and female pipe threads conform to the Dryseal American Standard Taper Pipe Thread (NPTF) Series which will provide pressure tight joints without the use of a lubricant or sealer. Use of these fittings with non-dryseal NPT pipe or hose ends is not recommended for high-pressure applications."
    http://www.air-way.com/pdfs/ssnptfdata.pdf

    So for a fuel system, that is rather low pressure, I am sure I will be fine to use the NPTF sensor in a 6AN fitting with a tap for a 1/8 NPT fuel pressure sensor. :)
    I thought I would throw this info into the thread to just expand the information collection on DSMTuners.
    #12

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