I recently replaced the oil lines to my oil filter, and decided to replace all brass fittings, also. I'm having a * of a time trying to find the right fitting to for outlet line to the timing cover. It appeared to be a standard 1/4x1/8. I bought two locally, and when I thread it into the cover, it almost goes all the way in, then the brass fitting strips. I have an original 90 degree (wrong angle, I know, but I had one), and it seats all the way with no problems.
I decided to go online and bought 2 from Jungle Jim, figuring maybe they were some super-secret thread pitch or something that my local auto parts place doesn't have.
I got my package from Jungle Jim today, put it in this evening; you guessed it, stripped out. Put the original 90 back in, seats with no problems. Compare threads, look identical.
I know I'm not over tightening the new ones, as it never even gets to the too-tight stage.
So, learned fellows, what is going on ?