Does anyone know the size of the threads for the grease filler plug on a Cruiser knuckle? I was welding up some 6 stud knuckles today and got a bit of weld at the start of the threads for the grease plug. Now the plug won't go back in.
So, size of tap needed would be appreciated. It appears to be a taper thread like a pipe thread.
A 3/8 NPT tap is perfect for totally jacking up the threads though!
After a bit of investigation the choices are 3/8 x 18 NPT or 3/8 x 19 BTPT(tapered pipe threads vs parallel pipe threads which is also a British standard.)
It for sure is not 3/8 x 18 NPT and I believe it to be 3/8 x19 BTPT.
I'm going to drill it out and retap to 3/8 NPT. 37/64 bit needed.
edit: Update---Hole drilled to 37/64, weld material ground out with a small stone. Hole retapped to 3/8 x 18 pipe thread. Used a brass flush plug which I though might seal the hole a bit better with the questionable threads. Done. 2 new 6 stud knuckles in the world and all is well and resolved.
