Thread taps

[John McIntire]

I remember reading an article in a magazine about underhood detailing, and I think it was by steve strope.
In it he mentioned tapping the holes so that fitting could be installe to sit nice and flush instead of them sticking out halfway.
My question is what kind of tap do you use? I know that theres one to start the thread, and one that finishes and bottoms out in the hole, and there are also thread chasers. Which do I use?
An example would be a pipe plug in your inatke or water pump, you'd tap the hole completely so that the plug would sit flush with the surface.
Thanks for your help guys!

[Madspeed]

you want pipe taps
and they would be named something like 1/4" npt, 3/8" npt, 7/16" npt, 1/2" npt, ect ect.

[FabUThis]

Pipe taps are tapered . If you go to deep you can end up with a loose fit .

[parsonsj]

Yes, beware the too deep pipe tap.

Don't ask me how I know.

jp

[CarlC]

I agree with the others, it gets ugly.

A better option is to use an internal hex tapered thread plug. They are available from Earls and several other sources.

Theres one just visible on the top of the waterpump in the engine picture on my website.

EDIT:

For S's and giggles I checked McMaster Carr. They have aluminum NPT pipe plugs with an internal square drive. They should also work well.

1/2"-NPT.

P/N 44705K335

$3.22 each.

OR

Summit Racing P/N EAR-993205ERL $4.50 each.