Although I'm getting to know my way in Imperial threads, I am still not extremely confident in my abilities to identify them.
I've got a set of crankcases for a late Model 50 that are missing the sump plug. It's quite a small hole with very fine thread. I've carefully tried fitting various old studs and bolts and the one that goes in deepest (but not fully, about 4 to 5 mm, though that might be due to it being used) is a 3/8-20-26 stud. The 26 tpi side that is.
So it seems the thread is 3/8"-26 BSC. Could that be right?
Probably 1/8" BSP (28tpi)…
- Log in to post comments
Sump plug threads.
Hi Tim,
Yes you are correct, 3/8" x 26TPI. This section of the crankcase is quite thin so needs a fine thread. Unfortunately this is too fine for aluminium and is easy to strip the thread. A quick fix for this is to re-cut it with a 10mm x 1mm thread pitch (25.4 TPI) which is just enough to restore the fit.
- Log in to post comments
Probably 1/8" BSP (28tpi)
John