Rudder Quadrant Bolt/Nut size

[senang]

I am installing an autopilot on my Hunter 38. The attached picture is from the installed bolt on the autopilot quadrant of the rudder. The bolt is exactlky 12mm diam. Living in europe, I have tried a standard 12mm metric nut, but it is totally unfit , it does not go more then 1/4 turn.
The picture attached is upside down for obscure communication reasons between iphones, imacs and this forum software.
Does anyone knows what standard this bolt is? ANSI or other? I am puzzled by the exact 12mm diameter, I would have expected 1/2 inch i.e.12,7mm.
The quadrant is marked (on the underside) Hunter Custom C-754, the retaining half circle is marked Edson A2052.
Any ideas?

 

[Benny17441]

What are the machining specs on the threads? From the picture it looks like "fine" threads. Fine threads usually run around 32 threads per inch with "coarse" ones around 24 threads per inch. You do not only have to match the diameter but also the threads number.

 

[Don12364]

Please see my response for the first time you posted this message.

 

[Jake N Eggs]

I am installing an autopilot on my Hunter 38. The attached picture is from the installed bolt on the autopilot quadrant of the rudder. The bolt is exactlky 12mm diam. Living in europe, I have tried a standard 12mm metric nut, but it is totally unfit , it does not go more then 1/4 turn.
The picture attached is upside down for obscure communication reasons between iphones, imacs and this forum software.
Does anyone knows what standard this bolt is? ANSI or other? I am puzzled by the exact 12mm diameter, I would have expected 1/2 inch i.e.12,7mm.
The quadrant is marked (on the underside) Hunter Custom C-754, the retaining half circle is marked Edson A2052.
Any ideas?

The pictured bolt appears to be a custom bolt with the threads machined onto the shaft rather than rolled on. The peaks of the threads appear to be wider than normal which may indicate that the bolt was manufactured on 1/2" stock, had the threads cut and then finished ground to 12 mm. The treads look like they are 1/2" - 13 which is UNC. If you hold a scale beside the threads and count how many peaks there are in 1" or 25.4 mm that will verify the thread pitch. If there are 13 threads per inch then my above statement may be correct.

Good luck.

 

[kloudie1]

Don't know if this helps.. shows threads that are "close"
http://mdmetric.com/tech/tic1e.htm

 

[senang]

I posted this on the Hunterownersforum, apparently something went wrong, I now see that this post shows up in Beneteauowners.com/S2Owners.com, hence my double post. Sorry for the confusion. In the mean time I have found out that it is a 1/2-13 bolt, 1/2 inch bolt coarse thread.