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MG MGA - Instrument mounting Thread size

Can anybody tell me what the thread type/size is for the mounting studs on the back of the dash instruments? Moss says that they are metric, but that didn't prove out. I'm guessing they are BA, but I don't have any nuts to test that.

I'm replacing the harness during a total restoration and frankly I'm too old to be chasing an intermittent ground under the dash later. I'm planning on a better mechanical connection by adding a second "squeeze" nut
to hold the ground lugs firmly on the stud instead of just depending on pressing against the flexible mounting brackets.
F. J. Bruns

Like you, I would have thought BA.

I've just measured the thread on an MGB speedo, which just happened to be in the dining room. It is 0.1565", which is a little under the 3BA size of 0.1614", so not too conclusive, I'm afraid.
Dave O'Neill 2

4 X 0.75 mm
Cheers,
D W DuBois

Moss gave me 4 x 0.5 and it didn't work. When I go out today, I'll pick-up some 4 x 0.75. looks like they may work.
F. J. Bruns

I have a collection of dashboard gauge 'nuts' which are the circular 1/2" diameter knurled edge type. Some are brass others aluminium and they are all threaded 3BA. I think it would be unlikely to find metric threads in these 1950s british gauges.....................Mike
m.j. moore

BA threads are 'sort of' Metric.
http://en.wikipedia.org/wiki/British_Association_screw_threads
John DeWolf

My supplier didn't have a 4 mm x 0.75 screw/nut and couldn't find any in his catalogs. Same with my Google search. Specialty?

I'm going with Mike on the 3BA. Now, any unique places that might carry small BA screws in the U.S. today? I had heard possibly model train stores? I would like to find a local source. I hate to pay ridiculous shipping charges for half a dozen nuts, But I would hate even more if they were the wrong size.
F. J. Bruns

Might be worth contacting Todd Clarke............Mike
m.j. moore

As said above, and as a modeler, a model shop would be a good bet although I only use 6 to 16BA. Also I have never come across odd number BA sizes, always even.

Paul
Paul Dean

https://www.britishfasteners.com/

-Del
D Rawlins

The correct answer is 3BA. Thought I would end this thread with a definitive answer for the archives. Bought 3BA nuts and they fit on both the MGA and MGB gauges. Thanks for all the help. This site is invaluable.
F. J. Bruns

F.J.,

For the US readers: From whom did you source the 3BA nuts?

Thanks,
John
JR Alexander

I ordered them from British Tools and Fasteners in Lyons, NY ( see Del's post above)
F. J. Bruns

This thread was discussed between 25/11/2014 and 01/12/2014

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