Totaly confused on Pryo Tap
 

Ok, I am looking to install a pryo and need to get the drill bit and tap. The instructions are asking for a 21/64" or 5/16" drill bit and a 1/8" NTP Tap. Everywhere I go all I can find is 1/4" and i can order a 1/8" but the size of 1/8" is way smaller then 5/16". Will a 5/16" drill bit and tap combo from the hardware store work?

Thanks for the information in advance.

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2005 2500 Crew Cab short bed 4x4
NV5600 3.73 With Limited Slip
117,000 Miles, K&N Drop in filter
12K Mile Marker on TRANS4MER MOUNT
BFG KO AT 275/70 R17

Pipe thread sizing does not match a tape measure size. Pipe threads are much bigger than what the size says. 5/16 is the correct drill bit for 1/8" pipe thread. Try Sears hardware or a Fastenal, they should have pipe taps.

my tap shows it to be a 11/32 bit with 1/8" pipe tap. guess each manufacture is different but works like a charm. wore it out and had to buy a new one a few weeks ago.

This might help
http://www.dieselmanor.com/dm_products/TAP1418.asp

11/32in or size "R'' bit for 1/8npt fitting I just tapped my manifold a week ago...

That is interesting, my tap shows 5/16 on the side. I guess you are right, each manufacture is different. The decimal difference is .3125 vs .34375 so I guess since pipe threads are tapered it just depends how deep you want to tap before it gets tight.

Seems like most of the older standard 1/8" pipe taps called for a 21/64" drill bit. I have noticed that most of the newer pipe taps(mostly foreign made) call for a "Q" sized drill bit. I have also seen some that use an "R" sized bit. If you are tapping the manifold for 1/8" pipe thread just keep in mind that the tap is tapered. You can get away with using any of the above bits just don't run the tap in all the way and cut the threads too deep. Just tap it about half way and then try the threaded thermocouple(or plug) If it doesn't want to thread in far enough then tap it a little at a time until it screws in a few threads or so. When I tapped mine, I used a 21/64" bit but the tap called for a "Q". The 21/64" bit is a little smaller than a Q but it worked fine.

You should'nt have any problems

Dave