Stuart BB Mystery Hardware

[wgreeley]

I recently acquired a Stuart BB apparently assembled by the first owner.

The hardware is not standard Stuart. It is in between 8BA (bottom) and 7BA (top). The diameter of the stud is 0.084" and has approximately 48 threads per inch. Does anyone have an idea what this thread might be?

 

[Jasonb]

Any chance its an undersize 3/32 Whit as that is 48tpi

 

[RonGinger]

Where are you? In the US 3-48 is a standard size, not used very often now but was common years ago. I dont have my table in hand, but that diameter sounds like #3.

 

[GWRdriver]

According to my book a #3-48 should be .099" major diameter which is quite ways from .084" (at least at this scale.) A 7BA is close to the same diameter (.098") but it's 53TPI. An 8BA is .087" diameter but is near 60TPI. The threads look reasonably well formed (full) so that suggests that the thread isn't a #3-48 on a stud which has had the major diameter turned under size, otherwise the tops of the threads would be flat. It's a mystery to me.

 

[rhankey]

How about a Whitworth 3/32x48TPI?

 

[wgreeley]

Thanks all. I tried a 3x48. The thread was good but it had too large a diameter. I'll try the 3/32 Whit.

 

[steamedlou]

This response might be a little late, but i have a few copies of old Stuart Catalogs. Aparently Stuart first introduced BA screws in the 1928 issue. chances are your dealing with whitworth as all the older engines would have used. Also Stuart offered both whitworth and BA at least through the 1933 issue which is the last one i have.