What is correct sized knurl nut for clock?

[mrfatboy]

I am taking apart my dash and while taking the clock out I found that it was only being held on by one small sized knurl nut (right side in pic).  I have extra larger sized knurl nut (left side of pic) that matches what is sold on Authentic Classics (the only size sold on that site that I could find).  I think both are 4mm.

Of course both do the job but I was wonder what is the correct one?  If it's the smaller one... PN? Source?

Thanks

[114015]

Hm, Boy ....,

Not more absolutely sure what I had (still have) on my car.
I think it is the left one, the thicker one.
The other one looks like 114/115 sedan (or so).



Achim

[ejboyd5]

If I remember correctly, the nuts on the ends of spark plugs are the same thread as the instrument mounting bolts.  Not "original," but they work and who will ever see them.

[wwheeler]

Functionally speaking, the larger OD nut will give you more torque when you go to take it off or put it on. To me, that is important as long as it has enough clearance around it to fit. And it will have more surface area to tighten up against whatever it is snugging up.

I'd use the left one, no question. Not sure which is original. I would shy away from the threaded spark plug end because it is both small in diameter and is smooth. You won't get much of a grip on that. This is where function should triumph over form. 

[BaronYoungman]

The nut is the same size that is on the brackets for the instrument gauges, Tach and Speedometer.  I am 100% sure.  So that would be the lager nut on the left in your picture.
Bob

[waltklatt]

Small one fits to the center cluster retaining nut(between the bakelight brown plastic backing and the bracket for holding the cluster to the dash bracket)  Unsure if this is clear to you. and the larger one is for all the gauges and clock.
Walter

[66andBlue]

Walter,
your memory is astounding! 
Here are the two part numbers:

[mrfatboy]

Mystery solved😎

Thanks Walter.  I was just about to agree with everybody else and move on.  It's perfect timing.  Dash is going back in now😀........ Correctly 😀