[behindpropeller]

I'm assuming rigid tapping of NPT in aluminum is ok?

Anything special I need to know?

This will be done on our TM-2, FYI.

Thanks

Tim

[fuzzyracing1967]

No differant than any other tap , but (there's allways a but ain't there) it will depend on how big npt I would think before it would stall out the spindal on a tm-2. Can tap 1/2 npt in aluminum on are ec-500 but it's pushing it

[Geof]

I have stalled a Super MiniMill trying to tap 3/8" NPT. The way I eventually managed to get some holes tapped was peck tapping going in less than a thread per peck.

And I held my hand ove r the E stop button just in case it stalled.

[Ken_Shea]

That really surprises me, have done a lot of rigid tapping but no NPT, would not have even crossed my mind that it would be very iffy on a TM.

What was the rpm?
What lubricant?

Thanks
Ken

[Geof]

That really surprises me, have done a lot of rigid tapping but no NPT, would not have even crossed my mind that it would be very iffy on a TM.

What was the rpm?
What lubricant?

Thanks
Ken

1000 rpm and extra rich water mix coolant. The thing with NPT taps is they are cutting on the full length because of the taper, regular taps are only cutting on the leading few, one or two, threads. Hand tapping NPT is hard work especially 1/2" and above.

[dertsap]

Interrupted thread tap will help lighten the load

[Ken_Shea]

In production one does not have the time to coddle machining processes, but if you did, would a specialized tapping lube be of help, like Tap-Magic for example.

You mentioned it stalled your machine, what method were you using to hold the tap?

[dertsap]

In production one does not have the time to coddle machining processes, but if you did, would a specialized tapping lube be of help, like Tap-Magic for example.

?

tap oil is a major help , it cuts down the possibility of thread tearing a lot , but so do the interrupted thread taps I mentioned above , spartap makes an awesome oil

[Ken_Shea]

Just did a little search on interrupted thread taps with NPT, appears to be no down side.

[Ken_Shea]

Just looked,
Actually have two sizes of that exact thing in 1/8 and 1/4, straight flute but still an interrupted tap, will have to try those and see how it goes.

[dertsap]

I don't recall ever using a straight tap like that , but it should work especially nice on deep holes , I find the pipe taps tend to not pack up as badly with chips and crap , which is most of the cause of spindle load and thread damage

[Medm]

Interupted NPT taps are nice for aluminum and other soft materials, just don't use them on hard materials = snap!

Someone mentioned 1000RPM - that's way to fast to tap with NPT! Normal speed for Aluminum would be around 100RPM or less if tapping 1/2NPT or bigger.

[Ken_Shea]

Another good option would be single point thread mill, would take a bit more cad work to draw the helix since that is kind of automated in a straight thread but still would eliminate almost all of the issues we have been discussing here.

[Ken_Shea]

Interupted NPT taps are nice for aluminum and other soft materials, just don't use them on hard materials = snap!

Someone mentioned 1000RPM - that's way to fast to tap with NPT! Normal speed for Aluminum would be around 100RPM or less if tapping 1/2NPT or bigger.

Never have tapped anything at 100rpm, thought I was being extra/ultra conservative at 200.


EDIT:
Just checked my threading software, 6061-T6 1/2-14 NPT recommended rpm was 455, standard tap, no HP.

EDIT: again
Not really sure on that now, was not a NPT tap.

[Medm]

I/we tap at 50RPM in stainless on a daily basis.

[dertsap]

the problem that I find with single point threadmill is that it is slowwww

100 rpm is slow , I think the slowest that I've ever tapped was about 350 , but that was with a (if I recall correctly) 1 1/8" straight tap X 2" deep in structural steel , gotta love big machines

[Ken_Shea]

I/we tap at 50RPM in stainless on a daily basis.

Can't speak to SS, never tapped any of that, some SS machines nicely, others do not.

[Ken_Shea]

the problem that I find with single point threadmill is that it is slowwww

100 rpm is slow , I think the slowest that I've ever tapped was about 350 , but that was with a (if I recall correctly) 7/8" straight tap X 2" deep in structural steel , gotta love big machines

Production would likely not be using single point but multi point.
Single point just covers a lot of ground with one thread mill.

[dertsap]

they're certainly handy for getting the job done (single flt)
most of the stuff I do now is small so its been a while since I've had the need of a threadmill , I used to use a lot of large multi point thread mills , both straight and tapered , they are great but the noise can make people pretty jumpy and take time to get used to

[Ken_Shea]

they're certainly handy for getting the job done (single flt)
most of the stuff I do now is small so its been a while since I've had the need of a threadmill , I used to use a lot of large multi point thread mills , both straight and tapered , they are great but the noise can make people pretty jumpy and take time to get used to

That's a fact, all tools have their own sound and do take getting used to, I have quite a bit of non professional time under my belt and I'm still jumpy.