School us on metric thread nomenclature, please.

   

Thread pitch is known 1mm.  Hex size is 27mm.

ID of threaded portion of the the nut peak-to-peak is nominal 19mm.

Is this considered a M20 nut, as in M20x1?

Thanks all !

Good Ridin'
slmjim & Z1BEBE

Yep, m20 x 1. (Aka M20 ultra fine)

Whatever the thread ID measures is roughly the tap drill size, you can confirm size and pitch on any thread chart by cross referencing tap drill size.

slmjim+Z1BEBE wrote:

Is this considered a M20 nut, as in M20x1?


 

No! the thread is measured by the outer diameter of the thread on the peaks.
That thread will be M22 X 1mm.
The inner trough measurement is near enough 20mm and the depth of a 1mm pitch is also 1mm so that takes it to 22mm which is very common for Kawasaki fuel taps and some Harleys etc..

Measuring the spigot on the tank will give the actual size which as zed said is 22mm

That's a Honda petcock Jim, what the heck ha. Missing the tower filtering sock and oring but remnants remain stuck to the tower. Yes, Zed's and Wookie's answers are correct!!    

wrote:

That's a Honda petcock Jim, what the heck ha. Missing the tower filtering sock and oring but remnants remain stuck to the tower. Yes, Zed's and Wookie's answers are correct!!    

   It is indeed. Z1BEBE's '93 CB750 Nighthawk.  The filter & O-ring were removed to ease measurement.  NLA from Papa Honda.  Aftermarket sellers claim either M18x1 or M20x1, and one claims M22x1, all for the same PN# for aftermarket petcocks for the same year.  Making us nuts...

   Metric thread nomenclature is brand-neutral and info on same could be useful to anyone here.

   There's no other forum we trust enough to accurately offer this, specific, tech info on metric threads.  The Nighthawk forums aren't on the same tech level as KZR.

   Reading through this thread, there's even differences of opinion here re: size.  Some online fastener / thread charts vary in description, but mostly tend towards M20x1 for the indicated  ID caliper measurement.

   To further muddy the waters (or not), bung threads are nominal 20mm. peak-to-peak, which may make M20 more believable.  Our desire is to get this done right the first time.
 

Thanks, all.

Good Ridin'
slmjim & Z1BEBE
 

Guys if that vernier is sitting on top of the threads then it is indeed M20 - M22 is the most common across Kawa, Harley etc (the bung I welded into the tank of my project is M22 in the same spot you are measuring)

Would this help in any way?

www.cmsnl.com/honda-cb750-nighthawk-1993...et-cock_16953me5005/

(I don't know what sort of shape the existing petcock is in)

Wookie58 wrote:

Guys if that vernier is sitting on top of the threads then it is indeed M20 - M22 is the most common across Kawa, Harley etc (the bung I welded into the tank of my project is M22 in the same spot you are measuring)
 

The outside jaws are firmly seated on the thread peaks of the bung.  The inside jaws are firmly seated on the thread peaks of the nut.

Good Ridin'
slmjim & Z1BEBE

slmjim+Z1BEBE wrote:

Wookie58 wrote:

Guys if that vernier is sitting on top of the threads then it is indeed M20 - M22 is the most common across Kawa, Harley etc (the bung I welded into the tank of my project is M22 in the same spot you are measuring)

 

The outside jaws are firmly seated on the thread peaks of the bung.  The inside jaws are firmly seated on the thread peaks of the nut.

Good Ridin'
slmjim & Z1BEBE

Then it is indeed M20 which ties up with what's advertised on Ebay for CB750, Nighthawk, CB900 etc