NTP

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06 Sep 2011 15:01 - 06 Sep 2011 17:30 #13006 by BigJohnT
NTP was created by BigJohnT
This subroutine creates a NTP pipe thread. I use it with ngcgui.

John

DON'T use this yet! there is an error.

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File Name: ntp.ngc
File Size:2 KB
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Last edit: 06 Sep 2011 17:30 by BigJohnT.

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01 Dec 2012 02:16 #27105 by jlviloria
Replied by jlviloria on topic NTP
John

I can help make internal NPT threaded. I am analyzing the file that you enclose the truth but still do not quite understand the subroutines.

I see you say not to use. because there is a mistake, I need do npt threaded:
1 "1/4 npt
1 "1/2 npt
2 "npt

can guide me how I can make these threads?

Jorge
Colombia

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01 Dec 2012 04:49 #27108 by BigJohnT
Replied by BigJohnT on topic NTP
To cut a tapered thread you need to use G33... maybe you can fix the ntp sub for everyone.

John

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12 Dec 2012 11:49 #27609 by joekline9
Replied by joekline9 on topic NTP
I just happen to be working on a simular project.
I will make a program for each thread size instead of a common sub prog.
I just started on 3/4 Male NPT. It works but not complete by any means.
I am posting now it to show the basic idea.
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12 Dec 2012 20:54 #27621 by BigJohnT
Replied by BigJohnT on topic NTP
Cool! Using the custom tab you can call it up any time you need it.

John

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13 Dec 2012 09:12 #27654 by joekline9
Replied by joekline9 on topic NTP
Here is a working file for 3/4" male pipe threads,
You can just change the parameters to do other sizes.
I will post more sizes when they are ready.

it seems to work properly. I don't have it doing the spring cuts yet.

Joe :)
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13 Dec 2012 20:16 #27663 by BigJohnT
Replied by BigJohnT on topic NTP
It would be so much easier to read the G code if you used named parameters instead of numbered.

Thanks for working on this.

John

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14 Dec 2012 11:47 #27718 by joekline9
Replied by joekline9 on topic NTP
Here are some G code files to cut NPT tapered pipe threads.
They now do the spring passes and auto calc the compound feed angle from parameters #50 & #51.
You can change parameters #39 thru #58 to cut any thread, straight or tapered.
If #39 (X Start Point) and #52 (X End of thread) are the same it will cut straight.

Normaly #51 (Z cut Depth) is 1/2 of pitch (#41). That gives you 30 degree compound angle of in feed.
#51=0.0 it will plunge in ( 0 degrees).
I will post more sizes when they are done.

John,
I should have used named params but this is my 1st attempt at params in LinuxCnc
and I wasn't to sure how to use them.
Thanks for the tip.

PS:
Maybee in a future release of LinuxCnc G76 could have an X word to allow it to do tapered threads.
What do you think.
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14 Dec 2012 19:37 - 14 Dec 2012 19:51 #27722 by BigJohnT
Replied by BigJohnT on topic NTP
I think there has be quite a bit of discussion on taper threads and no one seems motivated to actually take on the task.

Named parameters are your friend and make code so much more readable.

I converted one of your files to use named parameters...

John
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Last edit: 14 Dec 2012 19:51 by BigJohnT.

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15 Dec 2012 00:12 #27733 by andypugh
Replied by andypugh on topic NTP

Here are some G code files to cut NPT tapered pipe threads


There is a "gotcha" with tapered threads and G33. G33 moves at the desired pitch along the path, not along the Z axis.
This may not be noticable for a shallow angle, but does need correcting for.

(This may look like a drawback, and some people consider it a bug, I am of the opinion that it allows for more flexibility, creating scroll chucks for example.)

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