Fuse Box Retaining Screw

Hello again,

The chromed retaining screw for the front of the Fuse Box was missing from my car, however, I managed to source one from a friend. Unfortunately the threads need running over with a die to clean them up. I went through the Parts Manual and the Cover Screw isn’t mentioned as far as I could see. I’m interested to know the thread size. I’m guessing that it’s 1/4" BSF but would rather be sure before I run the die over it. I think that it’s time to invest in a set of thread gauges.

With my thanks in anticipation,

Tim

I’m surprised that the screw is chromed. But I would think almost certainly a BA thread.
I’m not familiar with MK Vs ut 1/4 " seems an overkill, If I had to guess I’d go for 2 BA or 3 BA.

Thanks Ed.

It appears to be chromed in the Service Manual.

The fuse box retaining screw on my Mark V saloon is 0.1815" diameter in the threaded region and close to 32 threads per inch. The 1940 American Machinists’ Handbook lists British Association 2 threads as 0.81 mm pitch, approximately 31.35 threads per inch, and Full Diameter between 4.580-4.700 mm, 0.180-0.185 inches. The 2 BA die fits that screw well on my car. The retaining screw appears to be bronze, no chrome on mine.

I measure 3/16" diameter and a 32 pitch gauge fits, so I make it to be 2BA.
That screw was used on a lot of different fuse boxes including SS and XK120, but I don’t recall ever seeing a chromed one.
The cover was painted gloss black, though sometimes you see polished ones on over restored cars.

Thank you for the information as always.

I didn’t have one so was flying blind.

I’m happy to leave it chromed.

The paint finish is black “Hammer Tone” which has the crinkled look to it and is in good order, fortunately!

Cheers,

Tim

I’m having a similar problem in the E-type forum to get thumb nuts for the gauge mounting studs.

Phil.

I got some for my early MG from NTG in the UK. Other MG specialists also stock these as they seem to be reappearing now, along with the brackets. These are BA threads however, but I don’t know if there was a change in thread standards during the Jag run of E types.

2BA and 10/32 UNF are identical thread-wise. You will find the head sizes are different. The nuts are physically different sizes too but one fits the other screw

Art

2BA and 10/32 UNF often are interchanged since they are so close thread-wise. The specifications for 10/32 are basic major diameter 0.1900" with 32 threads per inch. 2BA is basic major diameter 0.180-0.185" with 31.35 threads per inch.

Art, My immediate thought was that you had made a simple typo, but now realise 10/32 UNF is not 5/16 UNF as 10/32 implies. But yes, I realise in USA these small UNF threads are shown (I thought) 10-32 as a shorthand way of writing Number 10, or 10G (Gauge) with 32 tpi.

So the error was more a case of using the word ‘identical’ as 2BA (British Association) is not ‘identical’ to 10-32 (UNF), with ‘similar’ probably more appropriate. Indeed regarding practical fit, ‘near enough’ re interchangeability, if no advisable, if you don’t want to damage or strip a thread.

2BA threads have is 0.1850" Major Diameter, with 31.4 tpi (its actually a metric thread 0.81mm pitch, but BA is always quoted as 31.4 tpi), and a 47.5-degree thread angle.

Number 10, or 10G UNF or (10-32) is 0.1900" MD, with 32 tpi, and has a 60-degree thread, so really is quite different to 2BA. Given the closeness in diameter, they are seen to fit OK, but with only minimal force can easily damage/distort the thread if over a long engagement. If only a setscrew into a nut, the minimal width of the nut is sloppy enough within tolerances not to matter, but don’t over tighten. But I wouldn’t interchange No.10 and 2BA if you have a setscrew going into a tapped hole of some thread depth.

Easy enough to buy 2BA fasteners, so why use 10-32 setscrews into a 2BA threaded hole, as you find on many British/Jaguar/Lucas/Smiths components.

Roger

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I’m a retired mainframe computer engineer and over the years I amassed a quantity of UNF & UNC hardware from scrap machines. As it happens I ended up with more 10/32 screws than nuts so when I bought a pack of 100 2BA nuts I started using them without problems.

Art