Retractable threading tool - videos

[Jon]

Retractable threading tool. By Czech Machining.

2:07 video:

2:22 video:

[Ed Weldon]

OK so you've convinced me that your idea works. Pretty cool. Now; are you doing to tell me how to make one or buy one or a set of plans. Or just leave me with the motivation to design my own version and make it myself to fit my lathe?

[metric_taper]

After watching both videos, it appears that the threading tool bar holder, has a dove tail slide to prevent slop in the retraction mechanism.
I'm guessing that there's a rack and pinion gear that moves this in and out.
This youtube channel is a manufacture that is selling this tool. Probably why there's no detail.
The other oddity, he's operating the lathe without disengaging the half nut, so hard forward to reverse motor operation. I think that's a good way to damage motor contactors, but he could be using a VFD. You can't really tell as his right hand is shown on the engage disengage lever of the retraction tool, so I assume that his left hand is reversing the lathe, and moving the cross feed in for the next thread pass.
Also, I could see he disengaged the tool early on a few passes.
I like this tool that was seen here a few weeks ago as it's automatic on disengage;

He also has a mechanism that disengages the half nut.

[nova_robotics]

That's a nice tool. I could use something like that. I would probably put the lever on the back with a ball screw to push it forward and backward. Is there an eccentric cam that moves this? The tool in metric_taper's video is an eccentric with a spring return.

Anyway if you go to the Youtube channel, click on the video description, there's a link to this guy's website. He's selling them to the public for 9760 Kč, which converts to just under $500 USD. Not sure what shipping is like from Czech. Nice tool though.

[metric_taper]

The tool in metric_taper's video is an eccentric with a spring return.

From reading the comments, the eccentric is 0.060 offset so it throws 0.120 disengage in 180 degrees of travel.
What confuses me, is once it's triggered, the spring will push the eccentric, which seems to not be what I would expect. It appears to be a snap action. Just seems an eccentric would not work that way. I assume it's slightly overcenter during the thread run, and tool pressure on the material keeps that in place. OK, maybe that's why is snaps away, the force is from the tool pressure, and the spring just keeps it moving. Just seems it would get stuck once the tool pressure is gone.
I'll have to build one to see how it works.

[olderdan]

It could be more of a radial cam shape as in a ic engine rather than a simple eccentric

[metric_taper]

It could be more of a radial cam shape as in a ic engine rather than a simple eccentric

The guy that made the video said; "Cam is circular and .06" eccentric, providing 1/8" retraction."

I was thinking the same thing about an engine type cam lobe.
Clearly you want a snap action mechanism that retracts the cutting tool quickly. But it if did do it at a fixed rate, it would leave a nice finished thread pull out groove.