Turning internal Rope thread

[Ox]

Ah, you're thinking that the insert (?) goes in and out - actuated like a Sunnen Hone I guess?
"Retraction" would seem to be the hurdle there.
Puting enough neg in the tool to push back and not get stuck in the cut, yet positive enough to keep tool pressure as low as possible?
Seems likea challenge, but ...

Yeah, that could 'splain it Lucy.


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Think Snow Eh!
Ox

 

[David_M]

It gets to internal at 2:22:

 

[Ox]

I think that I see it now.
No tool retraction.


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Think Snow Eh!
Ox

 

[Alex_cn]

Hi David_M:
Apparently the OP is already doing that with successive G32 passes and it's taking way too much time.
In his first post he describe how he is doing it with a macro which looks like it picks the proper start point for each G32 pass.
I haven't looked at it closely, but he describes decent success except for the cycle time.
What he wants to do is the same rope threading canned cycle that a high end Okuma can do, and he shows the method in the link to the video also in his first post.
Have a look at the video...it's a crazy way to make a thread.
He is hoping to make a cheap lathe without a C axis do what the Okuma can do.

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com

HI Marcus,

I'm allready doing it in ID with the macro in my first post. I do OD on 6 meters bars with thread rolling mill (no cutting, it's deformed).
And yes, what I'm trying to do is to make a cheap lathe without C but encoder doing something close to what okuma does.

 

[David_M]

I want to talk about this some more.
Could I start by explaining what I think a rope thread is and see if you all agree?
A helix to start with:

Then an infinite number of circles with their center originating from along the helix (Shown with 30):

Shown with a computer's approximation of infinite:

Am I wrong in my assumption?

 

[Alex_cn]

I want to talk about this some more.
Could I start by explaining what I think a rope thread is and see if you all agree?
A helix to start with:
View attachment 366449
Then an infinite number of circles with their center originating from along the helix (Shown with 30):
View attachment 366450
Shown with a computer's approximation of infinite:

Am I wrong in my assumption?

Hello David,

It's is not really the case. based on your way of seeing it you would need an helix on with a radius of 1.6mm (thread depth) and with a pitch of 12.7mm. But and there is a big but the shape with the center originated from the helix isn't a circle due to profile of the thread.

 

[David_M]

Hey, Alex.
What is the major internal diameter for the one with a 12.7mm pitch and 1.6mm thread depth?

Image showing 12.7mm pitch and 1.6mm thread depth:

 

[Alex_cn]

Hey, Alex.
What is the major internal diameter for the one with a 12.7mm pitch and 1.6mm thread depth?

Image showing 12.7mm pitch and 1.6mm thread depth:

David here is the dimension of left hand rope thread R32.

 

[David_M]

I think I'm right after drawing the above to the specs you showed.
I could see this nut done in a CNC horizontal or vertical mill.
You would use synchronized movements in X, Y, and Z to keep the Centerpoint (of the circles) on the "guide" helix and advance an increment into the bore. Then using a G12 or G13, cut out to a circle 30.08mm in diameter. Repeat until you reach the bottom.

A series of circles centered on the 0.8mm radius, 12.7mm pitch helix form the thread's profile: