Lets Talk Taps

[Mudstud]

Grainger has my 37/64 drill bit on backorder for several weeks now so am looking at alternative places to buy. This is for drilling/tapping my gear box once again for assist. Going with 3/8-18 NPT. In doing so I noticed a couple versions of taps.

This one says 1/4 but it is teh pic they show for all taps of this nature.

Irwin Taper Pipe Tap, 3/8-18 NPT

And then there is this one.

Value 3/8-18 Nptf Hss Dryseal Pipe Tap

It looks like the second one might work better to get into the dead end holes- the viens. Might could work without having to grind a tap down.

The names of these taps brings up another question. The fat one says NPTf dry thread, so does that mean the first one requires a sealant when putting the fitting in? I have two taps like the first one.

 

[Mike D]

Most taps are designated #1, #2, or #3. A #1 tap has essentially no threads at the the end. They are several inches long. A #2 tap looks like your first picture, with threads starting at the end with a uniform taper. A #3 tap looks like the second picture, with an accute taper but fully threaded. A #3 tap would be used to chase buggered threads in a 90 deg elbow.
if you were to thread a hole from scratch you would use a # 1 tap to cut the threads. If your tap bottoms out without using the full length, you would then use a #2 tap to finish threading the hole.
Most taps ( and bolts) come in two thread sizes corse ( 3/8 - 18 ) and fine ( 3/8 - 24 ). Make sure you use the correct one.

 

[kennyw]

The big difference between those two taps is one is dry seal (NPTF) and the other is not (NPT). The NPTF threads rely on interference to create a seal so that sealant is not required if you have a full thread engagement.

However, since you are taping a steering box with less than full thread engagement I would recomend the NPTF tap AND use sealant of some sort.

Also McMaster-Carr is another good source for stuff like this.
www.mcmaster.com

 

[kennyw]

Most taps are designated #1, #2, or #3. A #1 tap has essentially no threads at the the end. They are several inches long. A #2 tap looks like your first picture, with threads starting at the end with a uniform taper. A #3 tap looks like the second picture, with an accute taper but fully threaded. A #3 tap would be used to chase buggered threads in a 90 deg elbow.
if you were to thread a hole from scratch you would use a # 1 tap to cut the threads. If your tap bottoms out without using the full length, you would then use a #2 tap to finish threading the hole.
Most taps ( and bolts) come in two thread sizes corse ( 3/8 - 18 ) and fine ( 3/8 - 24 ). Make sure you use the correct one.

Are you talking about pipe taps? Because they are different from UNF/UNC threads.

 

[GNERGY]

Home depot or your local hardware store should have the drill you need.
Tarey

 

[MNorby]

napa will prob have bit you need and I have 2 taps for the job, a normal one and one I lopped the last 1/2" or so off so I can run my normal one till it bottoms out then my shortened one till I get the thread I need

 

[SCOOBYDANNN]

www.mscdirect.com