OD Threading Lathe

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01 Jan 2011 23:40 - 01 Jan 2011 23:41 #6355 by BigJohnT
OD Threading Lathe was created by BigJohnT
This is the subroutine I use for OD Threading on the lathe.



File Attachment:

File Name: th_od.ngc
File Size:1 KB


John
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Last edit: 01 Jan 2011 23:41 by BigJohnT.

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01 Feb 2011 04:08 - 01 Feb 2011 05:01 #6910 by otto_pjm
Replied by otto_pjm on topic Re:OD Threading Lathe
Likely me being confused, but is parameter 3 the start / total diameter of the piece or the radius?
Or put another way, would the example in the screen shot make a 3/4 - 16 od thread or a 3/8 - 16 od thread.
Looking at the G76 code it seems to be the radius, or the difference between the drive line and the thread peak, where the thread peak is expressed as a radius.( I think )

I have yet to thread anything successfully, found this and thought it would be a great tool to get me started, and want to make sure I understand.

BTW, I thought putting the G76 image in with this might be helpful, but the more I look the less sure I am, it seems like you would need an explanation as to how the parameters get mapped, and it might get too busy. Something like this but cleaned up.



At any rate, John, thanks a ton for putting these up, and Dewey, you are some kind of crazy geek / artist hybrid thanks for the code, and I love your woodworking.

Pete
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Last edit: 01 Feb 2011 05:01 by otto_pjm. Reason: Adding image idea

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01 Feb 2011 13:24 #6921 by BigJohnT
Replied by BigJohnT on topic Re:OD Threading Lathe
otto_pjm wrote:

Likely me being confused, but is parameter 3 the start / total diameter of the piece or the radius?
Or put another way, would the example in the screen shot make a 3/4 - 16 od thread or a 3/8 - 16 od thread.
Looking at the G76 code it seems to be the radius, or the difference between the drive line and the thread peak, where the thread peak is expressed as a radius.( I think )


That example is for a 3/8-16 thread. The diameter + the X offset describe the start X position.

I have yet to thread anything successfully, found this and thought it would be a great tool to get me started, and want to make sure I understand.

BTW, I thought putting the G76 image in with this might be helpful, but the more I look the less sure I am, it seems like you would need an explanation as to how the parameters get mapped, and it might get too busy. Something like this but cleaned up.



At any rate, John, thanks a ton for putting these up, and Dewey, you are some kind of crazy geek / artist hybrid thanks for the code, and I love your woodworking.

Pete


I like the image idea and if you can post that with parameter 3 showing diameter somehow that would be great.

John

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01 Feb 2011 21:55 #6942 by otto_pjm
Replied by otto_pjm on topic Re:OD Threading Lathe
re-worked the image a bit, and I'm hopefully understanding better, put it with the th_od.ngc file and it should appear in the tab when opened.



Pete
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01 Feb 2011 23:46 #6945 by BigJohnT
Replied by BigJohnT on topic Re:OD Threading Lathe
LOL, now I have to figure out how to attach the image...

Thanks
John

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02 Feb 2011 00:15 #6947 by otto_pjm
Replied by otto_pjm on topic Re:OD Threading Lathe
It's automagic, once the tab exists, you just put the image (same name with .png) in the same directory. There's one option as to it's location, but I don't think I needed to mess with it.

Pete

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02 Feb 2011 14:13 #6958 by BigJohnT
Replied by BigJohnT on topic Re:OD Threading Lathe
Oh Cool! I love automagic.

John

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06 Mar 2011 23:11 #7612 by Pilotltd
Replied by Pilotltd on topic Re:OD Threading Lathe
BigJohnT wrote:

This is the subroutine I use for OD Threading on the lathe.


File Attachment:

File Name: th_od.ngc
File Size:1 KB


John


Just looking at altering this to do metric threads as per your tapping subroutine. 99% of threads outside the USA are metric ;)

Steve

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07 Mar 2011 18:05 #7618 by BigJohnT
Replied by BigJohnT on topic Re:OD Threading Lathe
Take a look at the tapping one. It is already a metric/inch choice and might give you some ideas.

John

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17 Apr 2011 21:24 #9014 by cwmk577
Replied by cwmk577 on topic Re:OD Threading Lathe
I have a question about parameter #6 (Thread depth)

I have been making test threads in 1/4-20 size. My chart says these have a major diameter of .250 and a minor diameter of 0.1887. Looking at the pictures on the prior page, it seems to me like parameter would be 1/2 of the difference between the major and minor, so I tried .031 (rounding off), which of course wasn't nearly deep enough. So, I tried again, using the full difference (.0613) plus .002" for Kentucky windage.

That didn't work either, so I jacked it up to .085", and my nut went right on. Checking with a mic, the unthreaded portion of the shaft was .250, and the threaded portion was .246, so the .085 thread depth was pretty close.

Anyway, I am trying to figure out how to get this "right," meaning that I can produce a standard thread size more or less right on the first shot. I can see a few possible sources for error in this:

1. I'm setting the hread depth wrong and/or mis-understanding it
2. My tool table offset is inaccurate
3. I touched off incorrectly
4. Need more spring passes (that won't take .015" off though... not on a 7x10 mini)

I am assuming that I could sit down and experimentally determine values that produce desired results for the common threads I use, but I want to make sure I've wrung the other problem possibilities out first. And I want to know what param 6 is supposed to be :huh:

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