Help Using A Tap

keybrdcowboy1 · Dec 20, 2014

Can someone please help me figure this out? I've never used a tap before and I have need to tap an already existing hole in the intake. I went out and bought a tap set and a brass fitting to put in the hole. Attached is a picture of the fitting and the harbor freight tap. The fitting says 3/8" so I used the 3/8" tap. On one hole I used a tap that says 3/8"-16NC. The 3/8" brass fitting I have will NOT go in there. I was able to get a 1/8" fitting to fit and so I put that in with Teflon tape. On the other hole I am using a tap labeled 3/8" NF 24. It made the threads and looks good to my eye, but the fitting still will not screw in to it. Can anyone tell me what tap I need to use in order to get this stupid fitting to thread in? Thanks for any help....

addermk2 · Dec 20, 2014

There is a HUGE difference between a 3/8-16 bolt, and a 3/8" NPT pipe thread fitting...

You bought the wrong tap.

keybrdcowboy1 · Dec 20, 2014

Okay....what tap do I need then? Or can I get a different fitting to match the hole I already tapped? I didn't see many different options at home depot or Lowes or AutoZone.....

addermk2 · Dec 20, 2014

addermk2 said:
3/8" NPT pipe thread fitting...

You bought the wrong tap.

hrm...

keybrdcowboy1 · Dec 20, 2014

Heh...so I looked at the 3/8 npt tap at harbor freight and that thing was way bigger than the one I used...matter of fact it was so big it wouldn't even fit into the tap wrench I have....and I couldn't find a 3/8 npt tap at the other places I went to....sigh...this shouldn't be this hard...

addermk2 · Dec 20, 2014

3/8 Bolt vs 3/8 NPT tap.

keybrdcowboy1 · Dec 20, 2014

And that npt one will work for the fitting I have? Looks too big...

RangerJoe · Dec 20, 2014

Pipe fittings are measured by the inner diameter of the pipe. Bolts are measured by the outer diameter. That's why two different 3/8 taps look so different. Lol, someone had to explain this to me several years ago.

Joe

keybrdcowboy1 · Dec 20, 2014

Ok...since I already started I'm going to keep the stupid questions coming...the 3/8 npt tap I have doesn't fit in the tap wrench I have...and I haven't seen a bigger one anywhere I've been...what am I supposed to use to turn it?

addermk2 · Dec 20, 2014

12 point sockets work well...

CarMichael Angelo · Dec 20, 2014

Sigh.......c'mon dude.
It's a tap for Christs sake, not a thermonuclear reactor.
3/8 NPT taps have a square end on the non-threaded end. What are you supposed to turn it with? Uhh,................. how about a Crescent wrench? A 3/8" 12 pt socket?, a 3/8 12 pt. box end wrench?, or the correct tap handle are just a few of the options that are rattling around in my head.

You're right. It doesn't have to be this hard.

And for the record,...of all the things that HF sells....... the worst things you can buy from them are drill bits, abrasives, and..........taps.

Saleen0679 · Dec 21, 2014

Per the Dorman site the 787-018 brass fitting is for 3/8" hose, but the threaded end is 1/8"MNPT

addermk2 · Dec 21, 2014

Saleen0679 said:
Per the Dorman site the 787-018 brass fitting is for 3/8" hose, but the threaded end is 1/8"MNPT

I didn't look that far into it. Just saw 3/8 and ran with it.

Thanks for the. Correction.

f8tlfiveo · Dec 21, 2014

madmike1157 said:
And for the record,...of all the things that HF sells....... the worst things you can buy from them are drill bits, abrasives, and..........taps.

Lol.... Yeah, this is definitely good info... Some stuff isn't horrible at harbor freight, but this stuff is junk.
I have the ratchet extensions and impact sockets, never had a problem with them.

7991LXnSHO · Dec 21, 2014

RangerJoe said:
Pipe fittings are measured by the inner diameter of the pipe. Bolts are measured by the outer diameter. That's why two different 3/8 taps look so different. Lol, someone had to explain this to me several years ago.

Joe

And National Pipe Thread is tapered so the more you twist it together, the tighter and leak resistant it fits. Bolt teeth are the same size for the length of the bolt. (Or at least the length of the threaded part.) So if you get one of each with the same threads per inch, it will not really fit right and seal or torque correctly.

keybrdcowboy1 · Dec 23, 2014

Thanks for everyone's help.... the trick was knowing the threaded part was 1/8 NPT. I didn't even think of looking on their website to see the specs, so thanks Saleen0679... I had a 1/8 NPT included in the Harbor Freight kit I bought and that worked great. Screwed right in with no problems after that. And to add to the list of stuff I don't buy at Harbor Freight... power tools that I expect to use more than once. I will not buy a drill or saw from them. If I only ever plan on using it once I might go for it, but I've had too many crap out on me in the middle of something for me to rely on them at all..... thanks again everyone....

jcyamaharider · Dec 24, 2014

Also be sure not to take the NPT tap too deep, they actually have an engagement length. On properly threaded NPT hole the fitting should only turn 3 times. That is when the sealing starts.

Help Using A Tap

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my rearend will smell so minty fresh,

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My wife likes my spool and blow-off valve.

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I leave the horn on while driving

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my rearend will smell so minty fresh,

My wife likes my spool and blow-off valve.

wanna catch the space herp

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