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Thread: M6 bolt thread pitch

  1. #1
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    M6 bolt thread pitch

    I drive a '99 XJ8 Vanden Plas. I am about to replace my thermostat housing. I purchased the necessary M6 x 20mm and M6 x 25 mm bolts for the job. Does anyone know what the thread pitch is for the original bolts?

    The guy at the parts department told me that all M6 bolts have the same thread pitch. I am skeptical of that info. Can anyone confirm if it is 1mm pitch?

    Thanks muchly.

    Pete.

  2. #2
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    OK, I decided to take a chance and try to remove one of the bolts without breaking it off. I got lucky. It came out very cleanly. So, yes indeed, the M6 x 20mm bolts on the thermostat housing are, in fact, 1mm thread pitch.

    FYI: I have discovered though that there is a "fine" thread pitch of .75mm out there too.

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    Quote Originally Posted by Imanonamas View Post
    OK, I decided to take a chance and try to remove one of the bolts without breaking it off. I got lucky. It came out very cleanly. So, yes indeed, the M6 x 20mm bolts on the thermostat housing are, in fact, 1mm thread pitch.

    FYI: I have discovered though that there is a "fine" thread pitch of .75mm out there too.
    Yes, but you're unlikely to encounter it. The standard 6/1 is what you find 999 times out of a thousand. Thread gauges aren't expensive. Why not invest in a few of the common threads and pitches?

  4. #4
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    That's a very good idea. It would be a good investment.

    I was concerned about the pitch because the A4 engine on MG's had bolts of varying size/pitch. I was constantly running into that problem. Mind you, with my Jag being a '99, perhaps all of the bolts are more standardized and uniform. It seems they are. That's reassuring.

    Thanks for your reply. I'm going to pick up a gauge this week.
    1999 XJ8 Vanden Plas

  5. #5
    Junior Member Bayern_jag's Avatar
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    Hello Pete,

    M6 without any additions is normal metric 6 mm thread with 1 mm pitch . This commonly used in European cars. Correctly writen a screw is eg. M6 x 20 where 20 is lenght.

    A 6mm thread fine will have 0,75 mm, 0,5 mm or 0,25 mm pitch. It is called eg. M6 x 0,5 x 20 where 0,5 is pitch an 20 is lenght

    I do not know a car where other as M6 is used. M6 in fine is very unusal in Cars even in my Triumph TR7 which has metric and inch (mainly UNF but also UNC, BW and others) which can be very confusing.
    Greetings from Bavaria


    Peter
    XKR MY2008, XF MY2013; Triumph TR7 1981

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