3/4 npt tapping

[Rocketmachinist]

I have to tap a 3/4 npt in stainless. I recently bought a floating tapping holder and was wondering about a few things. When I tap, if I want to tap deeper I adjust my Z depth in my program not my offsets right? If I adjust it in my offsets then It won't pick up the threads and run the possibility of double cutting. Right? Also, where should I get a good starting point for tapping depth. I have the plug gauge and this is my first crack at rigid tapping pipe threads. Is there anything I should keep in mind?

[mayday]

Hope you have a lot of horse power behind that tap.

I would threadmill it myself. much better control / finish / dependability

[GoetzInd]

+1 on the thread mill. For the same reasons as above and also you can just use cutter comp to "creep in" on you pitch diameter. Your gonna need a pretty mean spindle to rigid tap 3/4 npt in stainless. Go though just a couple of taps and you have the cost of a nice thread mill right there.

 

Mike

[robh]

used a floating holder when we didn't have rigid tap capability. now that we do,tap collets or thread mills, in your case, that's a large tap to push. when we did that size in the past, the machine couldn't do it all the way, had to finish the last by hand.you probably know but the tap also has a tapered reamer that needs run before tapping.

[Cad-Camr]

If you have to use a tap and cant thread mill just get it started and finish by hand. A good cutting fluid will help. If you have a lot of holes to do get yourself an NPT thread Mill or use a single point tool.

[Rocketmachinist]

I'm not doing a lot of holes just 15 total. But, we got the holder to make life a little easier.

[Jayson Kramer]

I would start with a tapered endmill to get the angle this will help in stainless when rigid taping.

 

If you think about the tap starts easy then as it tappers up it has to cut more and the machine need to work harder.

[Odell]

Go with the tapered reamer if you have to tap, I have done this a lot and it works great. A 3/4 pipe tap is nothing to shrug your shoulders at, I have seen these explode.(Collet's are bad for these!) Lock-er in good and tight and use your Z to adjust depth. Start shallow and work your way down.

[Tom Flyer]

I'd suggest Moly-Dee tapping fluid, too. Messy as hell, but saves about 5HP.

 

YMMV

[Philcott]

You might also want to get to the correct depth in stages. Peck tapping. This will allow you to get cutting fluid to the tap as it gets deeper. For that size I would probably expect 3 pecks. Do this by adjusting your "Z" move in the program.

[Jayson Kramer]

quote:

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(Collet's are bad for these!)

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We;; I understand the thought that they will slip. so go with the ER32 that are for tapping they have the locking notch for the different size taps. these work great as they do not let the tap slip.

[latheman]

"Also, where should I get a good starting point for tapping depth."

 

Another thing you want to consider on depth is coast of the machine (VMC). We have old machines so we have to watch that.