Th350 Transmission npt fittings to nps 

I changed my th350 transmission cooler line fittings from 1/4-18 npt to 1/4-18 nps. I used a 29/64 drill bit and clean out metal shavings before taping the whole. Used wd40 or some tapping oil.
I used a tapping socket I got from snap on guy and it was 3 pack of larger sockets. I put a link for the smaller set but are great to have. Let me know if you have any questions.
Russell 640520 -6 AN 1/4" NPSM Transmission Fitting www.amazon.com...
uxcell Machine Tap 1/4-18 NPS Straight Pipe Thread 4 Flutes High Speed Steel www.amazon.com...
Lisle 70500 Tap Socket Set www.amazon.com...