10"x12" Scratch built lathe

**jakemestre** · 03-15-2018, 06:45 PM

This is a major update.
The machine is working!
I'll start off from the last update. Here's a photo of the crappy, warpy, gluey, recycled stainless that makes up this machine.

Chopping it up with a Dremel saw that uses cutoff wheels. Mostly because I don't have a sheer.

Then I flatten it as much as possible and use a hand belt sander to get the brushed finish.

Afterwards I bend it on my little box break, and weld it with my Dynasty280x I love that tig machine!

More sheetmetal work.

I printed a cable dragchain mount that l's off for the x axis chain.

Unfortunately it was in the way of the connector used on the back of the turret so I had to redesign something that was much more compact.
I decided black could look a little nicer instead of the blue. I also made a nice little stop for the home switch on the Z.

That was one tough insert. G0 Y not Z while machining round tool holders.

Here's one of the internals of the turret. I ended up using a Leadshine closed loop nema17 stepper instead. The original stepper wasn't powerful enough to make it all happen with only 1.2A max current. I tried a 5:1 geared stepper but then there was too much backlash and the turret was missing the teeth for engagement. I also printed a really tightly toleranced pulley and there's only about 1 degree of lash now.

Round holders are finished and I drilled/bored the hole on the lathe itself.

The seal is printed in a TPU and very flexible. It'll be hard for chips to make their way into the hirth I think. The top of the turret was blindingly shiny I had to cover it with a little vinyl.

The router had a really really hard time cutting the 300 stainless. Even with MQL spray, perfect chip calculation it was really hard to get a clean cut.

It's really starting to look like a machinetool!

I successfully implemented an M6 remap today and the turret works perfectly. It even errors if it doesn't make it to position.
I'll be posting my complete config files for linuxcnc with a 5i25_7i76 setup. That will probably happen over on the linuxcnc forum so if you're interested I'll link it when I get that done.
That's all for now.
Next steps are to cut some metal for the coolant system. Then learn how to turn parts via fusion360.

**jakemestre** · 03-15-2018, 06:57 PM

Oh, forgot the photo of the cleaned up control box.

I've also got to fab some way covers. Telescoping style......

**DICKEYBIRD** · 03-18-2018, 09:13 AM

Wow Jake,you've really got it going you way! I really envy your Linux skills. That's why I had to go with the Centroid Acorn. The smart stuff comes pre-programmed on its onboard Beagle Bone.

I just noticed your encoder setup in an earlier post. Were you able to get LinuxCNC to correctly index the spindle for threading without a 1:1 pulley ratio? That's pretty awesome. Centroid is absolute in requiring that the encoder is driven at a 1:1 ratio for threading & rigid tapping.

**jakemestre** · 07-17-2018, 01:15 PM

Quick update:
Things are running pretty well!
Here's a shot of the current machine. I fixed the door so it slides perfectly now and opens up wide.

I love how it looks at night. Sort of spaceshipish.

I've made my first parts! Coolant nozzles for the machine. lol

And one purely fun project.

In Linuxcnc it seems to me that threading is really down to making sure that one revolution is exactly one revolution and that there's not accumulated error. I opened up a halmeter and looked at the revs counter directly. Then I put a test indicator on a jaw at 0 revs, moved the test indicator off the jaw with the z axis and rotated one revolution. That got me the rough the encoder scale for a single revolution but I needed to make sure that after say 20 revolutions I would reed 20 not 20.1 for the revs counter. It took a little while but I got threading down. If I remember correctly this was an M4 thread.

This a replacement part for one of the worm gears in my 3D printer. The nylon was wearing out much too fast, and I wanted a 2 start thread to speed up the output gear.

I found a screaming deal on a little power chuck, but no through hole is a challenge for prototype parts.

It seems like there's a never ending list of things to still do to this machine but that list is slowly shrinking. I still need to add cycle start/stop/feedhold to the buttons, and fab some waycovers, but otherwise the machine is pretty functional. And it's rigid! Way more rigid than I had hoped.

Here are a video of cuts.

**pippin88** · 07-18-2018, 06:02 AM

Regarding spindle encoder: yep, very important that the scale is perfect.
The easiest way it to have the encoder on the spindle, the index pulse at least will always be correct.

**ninefinger** · 07-18-2018, 07:17 PM

Originally Posted by jakemestre

I successfully implemented an M6 remap today and the turret works perfectly. It even errors if it doesn't make it to position.
I'll be posting my complete config files for linuxcnc with a 5i25_7i76 setup. That will probably happen over on the linuxcnc forum so if you're interested I'll link it when I get that done.
That's all for now.
Next steps are to cut some metal for the coolant system. Then learn how to turn parts via fusion360.

If you have that link for the Linuxcnc configs I'd like to see them. I have a 7i76E and the config would be similar (assuming the same functions).
Also - do share tips on using Fusion360 - especially the turning bits.
I have a tiny emco compact 5 with tool changer I'm using to learn with before I cnc a bigger machine.
I managed to hack up my toolchanger so its works with an open loop stepper (goes past the ratchet and backs up against it - sounds horrible when operating!)
Mike

**corry** · 07-29-2018, 11:07 PM

A couple quick questions:
First, this thread started in 2013. Was the time to cutting the pulls because of other endevours, funding, or something else? Or did it take this long?

Second: why the welds at the beginning? I’d imagine it wasn’t simply to raise the guides up a little. Was it machine constraints? (As in the machine that did the drilling and tapping)?

Third: I’m definitely not up on lathe turret work holding. I figured I’d read up a bit. You said you didn’t want to release your design which is fine, my question is way more basic. Are the parts holding the tools wedge shaped? I can’t see how the parts are retained otherwise but figured I’d ask.

I’m in the very early planning stages of what I’m going to do for a lathe. Your build is quite helpful