Sparkplug Top Thread

[chiefy]

Villiers MK25. Sparkplug is18mm does anyone know thread&pitch size for top of plug.

[billypurves]

When you say top of the plug .....do you mean where the HT lead is fixed?

[chiefy]

Hi Billy,Yes I do mean the thread where the HT lead is fixed( i did not ask the right question sorry about that another senior moment)Best Regards to you up in sunny Scotland. Keith (aka Chiefy).

[billypurves]

Hi Keith, Nothing wrong with senior moments tells you that your still looking down six instead of looking up six.!

Sparkplug threads.....I do not have a clue they might be UNC or Metric. Personally I would email Tim Green at the Green Sparkplug Company he is a helpful man and he will sell you them at the same time.

All the best from "sunny Scotland"

[chiefy]

Hi Billy, Thanks for your reply I am almost certain that the plug I looked at yesterday is 4mm but I cant be sure of the pitch i dont know if it is 05or07 pitch if I get stuck I will contact Tim Green.Best Wishes from sunny England hope its the same for you.

[Foden]

Some are UNC and some are Metric, depends really on the plug manufacturer. My 18mm NGK plugs have a different thread to the Champion and Lodge ones.

Pete.

[chiefy]

Hi Foden, I have champion & lodge 18mm plugs i am pretty certain the HT thread is4mm but i am unsure what pitch they are i know that 4mm is 05 and07 pitch but dont have anything to measure them with,thanks for that Best Regards Keith.

[Appletop]

They can be M4 metric, 2BA or UNC.

http://www.gsparkplug.com/ignition/spark-plug-accessories?cat=110

[chiefy]

Hi Villiers, you say they can be m4/2ba or unc its more complicated than i thought,I guess I need a nut of M4 size of a known pitch say 05 if it fits ok we then know the pitch if it dosn't then it will be 07 pitch.Best Regards from Sunny Yorkshire Keith.

[Darryl Ovens]

Sometimes another bolt/screw works better as a makeshift pitch gauge as they are longer.  Occasionally on the smaller sizes the clearance and "shortness" of the thread in a nut can allow them to seem to fit a range of pitches.
Cheers. Darryl

[chiefy]

Hi Darryl,I will try a M4 bolt of known pitch with screwon nut from top of plug ,thanks for that. Best Wishes Keith.

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