Instrument threads

[Erich]

On my choke(strangler) there are detents for setting the choke at different levels. There is a threaded bit, but no screw is attached to be able to set in the two detents. Does anyone know the thread size and what type of screw fits here? As well, what is the the thread pitch of the instrument fixing screws? These are the small screws which attach the instruments to the dash. They are instrument screws or raised countersunk, or what is called here in the US, an oval head. Further, what are the sources for these screws? Nickel plated, slotted.

Erich In Seattle

[NickB]

Hi Erich,

I think these are probably BA (British Association) threads including the choke grub screw.
I've tried to find some plated heads and they rarely surface, ordinary BA slotted round head machine screws are still easy enough to find though. It may be worth getting a small batch plated.

I bought most of my BA screws on eBay.
https://en.m.wikipedia.org/wiki/British_...ew_threads
Size 2, 4, 6 and 8 are possibly the most commonly available.

[AustinWood]

I have used stainless steel screws on the dashbpaord. They look very similar to nickel.
BA SS raised countersunk may be a bit difficult though maybe here:
http://www.a2stainless.co.uk/4BA-x-1-4-S..._ALJN.aspx

[Nick Lettington]

Of course the strangler (choke) grub screw is optional. Its an old topic much discussed... The positions out, almost in and in are almost useless. Two wooden cloths pegs are the best option to hold the choke in the necessary mid range positions, reduced to one to hold it at almost in. I find my choke sometimes snags on the intended grub screw. If I could be bothered with the faff of pulling out the dash I might offer to send it. (Brittle wiring puts me off though)

[Erich]

I have been able to get the proper grub screw for the choke detent. 6BA X 3/16 brass. A pita to install until I remembered I had several screw starters from Snap On(spring loaded screw driver that locks the slotted screw onto it). A life saver as I can barely see the screw, let alone thread it in.

Erich in Seattle

[Austin in the Shed]

I thought they were both 5 BA.The mounting screws raised countersunk, the one for the detent basically 1/8" dia bar threaded about 3/16" ,cut off with a screwdriver slot in it.ie no head.

[Erich]

Hi Dave, the fixing screws may be 5 BA. On my choke detent, I had ordered 4 BA through 6 BA just in case. Other's detent screws may be 5 BA, but in my case the 5BA was too large.

Erich in Seattle

[Erich]

I checked my instrument fixing screws today and they are 6 BA. At least comparing to existing screws, that is what they appear to be.

Erich in Seattle