What did I do wrong...NPT threading

[OldRedFord]

What do you guys think about threading it for a stainless bolt? I just dont like having only a few threads sealing it. The way I am I would be driving around worrying about it all the time.

[averagef250]

I don't understand why your NPT tap will not tap the threads. HSS is harder than cast iron, it will cut it. If you absolutely cannot get it to work the only alternative I could see is to face, drill, tap and taper the hole to accept the appropriate sized o-ring hydraulic plug. You aren't going to do that in a drill press.

[eggman918]

the book says that 2 thread engagement by hand is the correct depth/size for a npt thread,if it is there it will not fail
Try waterless hand cleaner for taping fluid I dont think that you can break a 3/8 pipe tap with 6" wrenches,however I understand you being cautious
each thread deeper you go the harder it will turn as you are cutting along the whole length of the tap,not the same as a bolt thread that cuts only on the first thread
hope this helps

[OldRedFord]

I don't understand why your NPT tap will not tap the threads. HSS is harder than cast iron, it will cut it. If you absolutely cannot get it to work the only alternative I could see is to face, drill, tap and taper the hole to accept the appropriate sized o-ring hydraulic plug. You aren't going to do that in a drill press.

Its not a HSS tap. Its whatever Irwin/Hansen makes their taps out of.

It will only turn in so far and then it gets pretty tough to do. Like said before I know the tap is not bottoming out.

Maybe I need to try drilling it out 19/32 or 39/64. Its at 37/64 right now.

[BobbyFord]

Permatex liquid teflon on the threads and it won't leak.

[eggman918]

A carbon steel tap will not be up to the job without luck
try the hand cleaner and see if you can gain on it 1/4 turn in at a time
I still think with short wrenches you will have to try to break the tap
if the tap does not say HSS it is carbon steel
Bobby Ford is correct use the goop and it wont leak it only has 13 PSI behind it

[eggman918]

If thread engagement is still a concern drill it 1/32" over and tap it again that will set it deeper with the same load on the tap

[71PA_Highboy]

I would be more than happy to send you a tap handle that will work.

Let me know.

Regards,

Eric

[averagef250]

I was unaware you can still buy taps that are not HSS. Pipe taps to end all.

[eggman918]

I was unaware you can still buy taps that are not HSS. Pipe taps to end all.

That is one hell of a load for carbon steel

[OldRedFord]

On the other side of the block I drilled out a buggard up threaded plug and used a 3/4" stainless steel set screw and sealed it with pipe dope. How do you guys feel on this holding?

[eggman918]

It only holds 13 psi,I would feel OK with it but I would watch it for a while "Lock-tite" might be better