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  1. #1
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    Default Assistance with thread ID

    I was planing on making an adapter from a straight thread to an NTP thread out of some brass hex bar. However I am having trouble IDing the thread. It is a temperature switch off of a Kubota block. See posted picture. I was guessing it would be metric, but can’t match anything.

    This is what I measure:
    Major Diameter 0.65”
    Minor Diameter 0.57”
    More course than 20tpi
    Less course than 18tpi
    More course than 1.25mm pitch
    Less course than 1.5mm pitch

    Any help would be much appreciated!
    Thanks! Brian65a9c6e0-fa5d-422b-b489-9f6b07bec20d.jpg

  2. #2
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    Just to make sure, the thread on the part is the straight thread? Sorry if I am misunderstanding. Based on your numbers, if it is a tapered thread, it looks very similar to the dimensions listed for 3/8-19 BSP.

    BSP Thread Chart with BSPT & BSPP Pipe Fittings Dimensions & Sizes

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    Thanks jspivey, it is a straight thread, no taper. But it looks BSPP in the chart you linked to. It may not be an actual Kubota part, and it did come from Britain, so that may explain things. Next i’ll Have to figure out how to get the lathe geared to 19Tpi.

  4. #4
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    Parker Hannifin offers lots of of adapters including many variations between BSP and NPT.

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    It's been my experience that most Japanese hydraulic fittings are BSP, so the thread is not unknown in Japan.

    Dennis

  6. #6
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    I think I can do 18.963 TPI on my SB-9. I haven't tested that to be sure the gears will physically fit, but the math does work out OK. An idler or two may be needed. Lead screw = 8 TPI. Stud gear = 54 teeth. Screw gear = 32 teeth. With a 4:1 compound between them. That's probably close enough for your purpose. And those numbers should work with any lathe with an 8 TPI lead screw.

    But I am not sure I am still allowed to talk about it here.

    A 19 or 38 (2 x 19) tooth gear in the gear train should allow you to do it on any lathe with manual change gears. You would have to do some experimentation and/or calculations on one with a quick change box. Perhaps set the box for 18 TPI and use a 18:19 or a 36:38 compound between the normal gears.

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    This may be useful and they carry quite a few British to other adaptors:

    https://www.discounthydraulichose.co...read_guide.pdf

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    guys thanks for share this information.

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    A few clarifications. The reason that these Kubota fittings have BSP threads is nothing directly to do with those fittings or other parts being made in UK and therefore having a 'British' thread. BSP and BSPP were some time ago adopted by the International Standards Organisation (ISO) as their standards for pipe thread. That means that you will find them on many types of products manufactured around the world, with the exception of North America, which has generally stuck with NPT. Whilst it might seem odd to use a Whitworth 55 degree threadform for an ISO standard thread this is the standard, and you are very likely to find this on Japanese, German, British etc products.

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    This is off of a Beta Marine Engine, which is a British company that uses Kubota blocks to make a marine engine. Beta makes the heat exchanger exhausted riser, raw water systems. I was assuming the thermostat housing was a Kubota part, but it very well may not be. Will have to look a little closer. I have some tapered BSP taps, as I have run into this a long time ago, but didn’t really think about a British straight thread. And none of my thread gauges have a 13.

    The lathe I normally cut threads on doesn’t list a 13. My other lathe has a standard gearing for 13tpi so I should be all set. I normally don’t thread on this lathe so it didn’t even occur to me yesterday to go look. It was getting late last night.

    As for an off the shelf adapter, something may exist, but I am going 3/8BSPP to 1/2 NPT and the temp probe is a little long anyway, I have the material, so it shouldn’t take long to turn something out, and I can just make exactly what I want.

  12. #11
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    The lathe I normally cut threads on doesn’t list a 13.
    And here I thought we were at 19 TPI

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  14. #12
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    Thanks everyone, cut a 3/8-19 BSPP thread this morning and it is going to work good. The thermostat housing is stamped Beta, so it is British.


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