O/T NPT EXTERNAL THREAD

[DavidB]

When making an External NPT can you buy off the shelf 1 degree and 47 min cutters?

 

You can buy Tappered thread mills so I thought the Taper needed for the External OD would also be an off the shelf item.

 

Thanks

[mrainey]

I couldn't find any ready-made a few years ago, had to have some HSS end mills ground.

[?Mark]

quote:

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When making an External NPT

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David, it should be the same tool you use for internal npt threads

 

When doing some crazy threads (acme and so on...) on a mill I use single point lathe tools.

Takes a bit longer but the tool is pretty much off the shelf.

 

hth

Mark

[Philcott]

Mark,

 

I think he is looking for a tool to mill the od of the thread, not cut the "v" threads. A tapered emill.

 

Phil

[?Mark]

Possibly, but he could "surface" this taper with a bull nose or ball em for that matter quite quickly.

 

But I'm not sure here either Phil, so that's why I put there.

 

Mark

[DavidB]

Mark,Im after a tapered endmill to cut the tapered male shape before thread milling.

My point is that you can but a tapered thread Mill cutter so why not the same angled tapered cutter in an endmill to prep the Diameter first.

 

Yes I can surface machine the taper,but a tapered cutter would be quicker.

 

I have to cut 1000 External NPT threads on a 5-azis Vertical machine.

 

Thanks

[DavidB]

For others future ref, when cutting an External or Internal thread with a thread mill cutter.The thread mill tool will cut the taper of the thread and also the taper of the OD for External and MD of an Internal thread.So only parallel preperation is needed.

 

[mrainey]

quote:

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The thread mill tool will cut the taper of the thread and also the taper of the OD for External and MD of an Internal thread.

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Will the tool last as long and give as nice a thread this way? I've never tried it myself.

[?Mark]

quote:

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Will the tool last as long and give as nice a thread this way? I've never tried it myself.

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On I'D npt threads I never prepped a hole with a taper and tool life was pretty good (several hundred + good threads)

 

I thought it would be similar with male npt (never done it though), which David just confirmed.

 

Mark

[Mjölnir]

Kind of crude, but you might be able to (hand)grind some clearance on a tapered pipe reamer and use it as endmill to take several light passes.

[DavidB]

quote:

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On I'D npt threads I never prepped a hole with a taper and tool life was pretty good (several hundred + good threads)

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This OK if your using a tap or a thread mill. But if screw cutting is Tapered preperation neede?

 

[crazy^millman]

I always did the taper keeps the top of the thread even and keep it from knife edging as well on the first couple threads.