Thread form on Engine studs

[harry wilkinson]

Can anyone tell me what the thread form should be on the engine mounting studs for a ’47 engined Squirrel. I measure 55 degrees (optical comparator) and 20 TPI on the old studs. Not 5/8 BSF, too many TPI and not a cycle thread, which is 60 degrees. ❗

[radicool]

Hi Harry,

I think you’ll find there 5/16″ BSF (22TPI).

Laurie.

[Anonymous]

do you mean the studs (like carb, exhaust, door straps) or the 3 long transverse bolts that run right through the frame and crankcase?

[radicool]

Hi Harry,

Sorry, had a senior moment. Having reread your post after Richards query
I’m sure you are referring to the engine mounting rods.In which case it’s a
5/8″X 20 TPI 55 degree thread.

Laurie.

[harry wilkinson]

Laurie, thanks for the input, 5/8 – 20 with a 55 degree angle is what I measure. I can now go ahead and machine cut the threads on my new studs. Richard, I’m so sorry I did not learn of your services sooner. I’ve just returned from a visit to your neck of the woods and would liked to have met you and seen your facilities.

[Author]

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