Ammeter stud thread

[Boomlander]

Hi all,
Can anyone tell me the thread size of the fixing studs on the back of a Smiths 30 0 30 ammeter so I can get some nuts?

[les]

I’m going to say 2ba, as with a lot of electrical stuff.

[Boomlander]

Thanks, I will let you know.

[Boomlander]

Turns out that the clamp stud threads on the Smiths Ammeter are 3ba.
Not sure if it's the same for all instruments though.

[les]

Oh dear, sorry.

[philthehill]

The single securing stud for Smiths oil pressure gauge PG1301/00AR is not 2BA or 3BA.
I have a full set of original LAL BA taps and dies and none of them fit.
I have yet to determine what thread it is. Once I know I will post on here.
Phil

[oliver90owner]

Just one example of a great number of thread gauges. Some are likely better than others, of course. I have two or three similar sets knocking around plus several hexagonal discs I brought home from Ca. They are all in use occasionally.

https://www.ebay.co.uk/itm/372165778297 ... BMxryCmfZg

[philthehill]

Having used my Moore & Wright vernier gauge, Moore & Wright thread gauges and referred to my ZEUS data charts this what I have decerned.
The securing stud is 5/32" O.D.
The thread TPI is 32.
So, with reference to the ZEUS chart, I believe the thread to be 8 - 32 UNC. (Unified screw threads for attachment under 1/4").
I have just ordered a 8 - 32 UNC tap and die set to prove or disprove the thread.

[oliver90owner]

I believe the thread to be 8 - 32 UNC

As long as the thread form is 60 degrees. Alternative would be Whitworth - possibly dependent on the age of the meter?

[philthehill]

The 8 - 32 UNC tap and die arrived today and I can confirm that the single threaded stud on the back of the Smiths oil pressure gauge is 8 -32 UNC.

[NETTIE]

I had this issue with my Smiths oil pressure gauge 3ba didn't fit so i bought 2 of the knurled aluminium round nuts and recut them on the original steel studs on the back if the gauge worked a treat.
I know this isn't the engineers route to take but at the time solved a problem.