[Mgs] MGA 1600 seat back threaded bolt size

[Barney Gaylord]

Robert, --- I'll give it my best shot.

The Service Parts List does not break it down to 
the level of that bolt.  The Seat Assembly -Less 
Cushion includes the two-piece frame and the pivot bolts.

The bolt is actually a shoulder bolt.  It passes 
freely through the hole in the seat back rest, so 
the backrest will hinge on the shoulder bolts 
when the bolts are fixed in place.  I think there 
is also supposed to be a thin thrust washer in between the moving parts.

The upstanding ears on the seat base frame are 
supposed to be threaded.  Pretty sure it is 
5/16-24-UNF thread.  The shoulder bolt screws in 
until the shoulder hits the bracket, and it stops 
turning.  Then the nut is installed inside and 
screws on until the nut hits the ear and 
stops.  Tighten gently, as it is a jam nut to fix 
the shoulder bolt in place.  If the female thread 
was stripped out of the ear, the shoulder bolt 
may hold in place anyway, as long as the nut is 
secure.  I don't remembwr if the thrust washer 
should be trapped under the bolt shoulder, or if 
the washer fits free spinning over the shoulder.

So there is no factory specified part number for 
that bolt in the SPL, although there surely was a 
real part number at the factory.  It would be 
nice if someone could find that part number, but 
the world has effectively done without it for 67 years.

I wouldn't mind making a drawing of the bolt, 
just that I don't have one in hand to measure at 
the moment.  I suppose I could take my car apart 
to "borrow" one long enough to measure 
it.  Problem is. my seats are not original, 
having been replaced with new assemblies from 
Moss Motors a few years ago.  With my luck the new bolts might even be metric.

Barney Gaylord
1958 MGA with an attitude
http://MGAguru.com


At 10:00 PM 6/17/2022, Robert J. Guinness wrote:
>....
>The MGA 1600 seat backs are attached at their 
>base by a threaded bolt that screws into 
>threaded holes in the frame base and finishes 
>with a nut to hold it all together at the pivot 
>point.  Does anyone know the dimensions of that 
>bolt?  It is not in Moss's exploded diagram or 
>the MG 1600 Factory Service Parts List.
>
>Robert Guinness
>....
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