NPT Thead Milling

[Guest]

How would one go about doing an internal NPT thread? Just as you would a regular thread mill?

 

Thanks!

[Guest]

Here's a previous thread about this

 

Linky

 

[Guest]

Ok, so I presume that based on this I just need to set basic thread stuff then give it a taper angle. Is that right?

 

Your example, John, was MC 9, and I don't know 9 all that well....but anyways... what is the taper angle designated it? "/ft? The help file says nothing of it.

[Guest]

quote:

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Ok, so I presume that based on this I just need to set basic thread stuff then give it a taper angle. Is that right?

---

Yup,

 

The angle should be 1.7889

 

Use the tip diameter as the tool dia

 

BTW, threadmilling in X and V9 work the same way

[medaq]

In version 8 I notice one thing that can be a pain in the xxxx to figure out why and how to change the diameter of the thread you want to cut.

 

toolpaths-nextmenu-circ tlpths-thread mill

 

Anyhow if you click a point you have the option to change the major thread dia, If you chain a contour you dont have that option and is greyed out. Only way to change the major dia is by changing the size of the contour. So imho picking points makes it alot easier in version 8. Dot know what 9 and 10 are doing...

 

Also having a npt thread gage is worth its weight in gold to make sure you are at the correct depth.

 

Jim

[Guest]

Jim,

 

It all depends how you draw.

 

I don't like using the points method. I hate it when I open an old program and all it is is points. I create setup docs and layout prints and such so it helps to have it drawn out the way you want the operator to see it. I model everything out, thus using the Ø of a hole is easier for me. Changing the diamter, that's what cutter comp is for.

 

But yes that same option is available in V9 and X

[Guest]

Pardon my mental brain fluff, but why exactly is it 1.7889?

[crazy^millman]

that is the taper angle on NPT threads is why. 3/4" per foot taper I believe.

 

Linky 1

 

Linky 2

 

HTH

[DavidB]

When I do Internal or External thread milling I just for (Internal) drill a 8.4mm hole for 1/8" NPT. Use a TAPERED 1/8" NPT threadmill as I would a normal thread mill in a straight thread.

I start from the top and go down the Tapered threadmill will automaticly put the taper on the thread major and minor diameters. I start from the top only with tapered threads because starting at the bottom is to big a cut, starting at the top the cut gets heiver as the tool goes down. No need to taper cut the thread.I use a circle as the geom this makes it easier to adjust size just edit the diameter of the cicrle and repost.I use wear also to get final size on the machine.

[Reece L Gibson]

1 degree, 47 min 24 sec

Convert it to a decimal of degree

1.79

[Guest]

Alighty. I am getting the NPT concept, but I think I am missing one thought...maybe I just am brain farting again.

 

How do you know what size of circle to draw as the geom. for the npt thread mill? Persay I want a 3" NPT, TDS is 3.25, so do I make the hole 3.25" and it knows that I am trying to do?

[DavidB]

Have you got ME consultant? Me consultant Pass word swiss

Its a gr8 tool.

[heavychevy2155]

why not just draw it small and use cutter comp, then just recut part to proper size. Works for me.

[Guest]

Never done it that way, Heavy. So what you say is (example of 3" npt) drill the 3.25" TDS hole and run the thread mill thru it, then reset and use a G41 and offset in small increments until you get standard pipe depth (3.5 full turns or whatever it is)?

[heavychevy2155]

yes sir, I couldnt have said it better myself.