Rudder quadrant bolt & nut

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senang

.
Oct 21, 2009
316
hunter 38 Monaco
Hello all, I am in the process of installing an autopilot on my 38. On the autopilot quadrant arm a 35mm long bolt is installed. I have a picture of it but I cannot find a way to upload it from my iPad. i will try later when I am behind my home computer. I measured the bolt at exactly 12mm diameter.
My question: What nut fits on this bolt. The quadrant is marked: Hunter Custom C-754. The retaining half circle is marked Edson A2052.
It is not a metric 12mm bolt, these are easy to find here in Europe, but they don't even go a half turn on the bolt.
 
Don12364

Don12364

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Dec 2, 2003
1,637
Hunter 376 Warsash, England --
Despite the American Metric Conversion Act of 1875 and the Metric Act of 1876 followed by the Metric Conversion Act of 1975. The public response was to ignore this almost completely.
See below:-
"The public education component led to public awareness of the metric system, but the public response included resistance, apathy, and sometimes ridicule."

The result is that just about all the nuts and bolts on your boat, other than the engine and items sourced internationally, will be SAE (Standard American Engineering) now replaced with UNF (Unified Fine) and UNC (Unified Coarse) threads with corresponding nuts and bolt head sizes. Some manufacturers will actually make products specially for the American market.
You are advised to buy a set of SAe/Unified spanners as these differ from the metric sizes in almost every case.
Please see the UNF/UNC thread chart on this link:-
http://www.carbidedepot.com/formulas-tap-standard.htm

Regarding your ½" bolt, I would expect it to be UNF ½-20 tpi or UNC ½-13 tpi. I would expect it to be 0.5" (12.7mm) diameter, a little less over the threads. If it is not threaded into the quadrant then you could replace it with an M12 metric fine but this bolt will be 0.7mm loose in the hole, though this should not be a problem as there should be a washer under the head anyway. There is no metric equivalent nor any of the old British BSF or Whitworth sizes that will fit properly.

Alternatively, if you can find a garage that services American cars, they might be able to help.
Or you could Google an e-Bay source in the USA and have some mailed to you.
 
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