Edit:
This would appear to be a 3D printed pattern that is burned out in an investment process, and then cast with aluminum or some other metal using the typical investment casting method.
So not really 3D metal printing at all, but rather investment casting, like lost PLA, if I understand it correctly.

I will have to read up on this method.
I don't understand it yet.


 the service has been launched as a more cost-effective alternative to Direct Metal Laser Sintering (DMLS).
“By combining additive manufacturing with investment casting, we get the best of both worlds:


https://3dprintingindustry.com/news/metalmaker-3d-launches-rapid-prototyping-service-for-3d-printed-metal-parts-142735/


https://metalmaker3d.com/

<a href="https://www.youtube.com/watch?v=YDIW8kITAM0" target="_blank">http://www.youtube.com/watch?v=YDIW8kITAM0</a>



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Having tested a lathe last year with a factory fitted ELS it is a nice feature to have.

The cost of the electronics these days from the likes of Aliexpress hardly make it worth doing your own thing and there are a lot of features and any sensible thread pitch or feed rate you want be it left or right hand. You can buy the same system as fitted to that lathe for very little money.

Running in reverse is useful to cut away from a shoulder but if you are able to set a length on your homebrew system then not really needed.

<a href="https://www.youtube.com/watch?v=tB7MaCHxQQ0" target="_blank">http://www.youtube.com/watch?v=tB7MaCHxQQ0</a>

After over a week of work trying to re-engineer what I'd done in software, I've finally managed to get my program and gear working well enough to take iot out to the shop and temporarily connect it to my lathe and stepper motor. It's all still laid out across the bench, not the neat unit I envisioned, but I was able to get the leadscrew turning after making a coupler for the encoder, and a bracket to support it.

I also had to set up a DPDT center-off switch in my spindle motor controller (a treadmill MC-60) to allow me to reverse direction of the spindle. That is how I will back off for each pass during thread cutting. Finally, I was ready to try this rig out. I chucked up a piece of scrap aluminum, and set the switches for 13 TPI. Then took a light pass. Below is the first cut on my homebrew ELS!

Very excited about that -- only one slight flaw in the ointment...... it was a perfect 14 TPI groove. Um guess I need to subtract one from a loop index somewhere in my code! Probably forgot that zero is a number. 

  Looking great and there's going to be some weight in those when they're complete.

You could leave the big end slot short of that hole that is a bit close to the turned section, it will be covered by the strap.

Bench grinder, belt sander/linisher or even an angle grinder would do.