TR2/3/3A 1960 TR3A Instrument Cluster Ground Post Screw

[Tinkerman]

Working on wiring the instrument panel and joining the wiring harness to it. On the back side of the panel there is a ground post that several ground wires go to. I do not have the screw that goes in there. Don't really know if I ever did have it. Looks like about a 1/4 X 20tpi, but my attempts to prove that have not been comforting and I sure don't want to force anything.
Does anyone know what is supposed to go there?

Any info greatly appreciated.

Tinkerman

 

[TR3driver]

I can check tonight, if no one knows offhand. But I would guess that they are BA threads.

 

[martx-5]

Did you try a 1/4"-28? Most of the screws on the TR3 are fine threaded. I don't remember what size was in there, as I never fully removed that set screw.

If they are BA threads as Randall suggests they might be, here's a BA thread chart. The dimensional data might help determine what you have there.

My experience with my TR3 indicates that most screws smaller then 1/4" are BA. 2BA and 4BA being the ones I've run into.

 

[PeterK]

I think that because it's electrical then it's probably the same as the screws in the fuse box and regulator - 1/4x26 British thread. Try swapping one and try it for size.

 

[martx-5]

1/4"-26 would be a BSC (British Standard Cycle thread).

0AB threads are close to that, measuring .236 x 25.4tpi.

I love this kinda stuff. Let's get to the bottom of it.

 

[PeterK]

I am certain of the regulator and fuse box size because I bought some from Holden UK. But the ground screw size is _______.

 

[TR3driver]

Well, 1/4-26 it is. I can't tell for certain, but they look like 55 degree threads to me, making it 1/4 BSF rather than BSC.

At any rate, the screw from a control box should work fine. Slightly different style than the original screw, but it's not like anyone will see it.

 

[PeterK]

The only place I've EVER found them https://tinyurl.com/y9hxuug

(Tink, PM me your address and I'll mail you a good used one)

 

[martx-5]

The place that I linked to for the BA and BSC/BSF charts, also sells tools, taps & dies, and fasteners in these British sizes.

 

[Marvin Gruber]

Tink,

I'm late to this party, I have spares and fairly close to you, just let me know if you need something.

Marv