Let's make something real on the CNC Bantam!

Surely not?

Well I seem to have a working-ish CNC lathe on my hands finally. So let's get busy and show (if) it actually works. 

Currently I have a plastic wheel that was liberated from the Blidgeport quill feed when I converted it to CNC. It looks shite but a pukka replacement would have required a fair bit of manual turning along with some spline milling. My plan was to eventually replace the temporary plastic handwheel on the cross slide (sorry - "Z axis") with the original micrometer dial. And what better a test piece to make on the CNC lathe - "physician heal thyself" and all that.

The job comes in 2 phases - firstly turn up the spindle itself, then over to The Shiz to machine the splines for the micrometer handwheel.

CAD and CAM for redesigned shaft:

Here's the original assembly I'd designed for the conversion. It would have retained the original power crossfeed drive pinion and would have required the ballscrew extension to extend through its centre, along with a small diameter splined section.

As I no longer plan to refit the apron and don't need the original drive pinion, I can simplify the ballscrew extension like the following. It's pretty simple, apart from the spline which I can't avoid if I plan to retain the nice micrometer dial handle.

I have some ~28mm mystery metal that looks suitable for the job. It has rusted slightly, which suggests it's some form of mild steel at least. Let's set it up as the stock in Fusion and create the toolpaths.

Here's the roughing and finishing operation for the "back" end of the part:

And the roughing, finishing and threading operation for the "front" end of the part

Right, here is the beast in its current glory:

Tool setup. First, get the tool height(s) set up:

Then do the touchoff operation, to avoid a bad experience when the tool needs to be changed from tool T4 (roughing / finishing) to tool T6 (threading). It's different to a mill although you still need to issue a G43 at some stage. However, the gmoccapy GUI buttons seem to handle the touchoff including the tool changeover. 

If in doubt, a T4 M6 does the tool change and a G43 T4 handles the tool length offset. And as it was my first time with this GUI, I did copious sanity checks to ensure the tool offsets etc were being handled correctly...

Off we go:

First stage roughing and finishing looks good to me. Of course, the finish tends to be better when you take a decent cut with carbide tooling, so the "finish" skim resulted in a rougher finish. Perhaps I should have used a ground insert for these light / finishing cuts but it's still fine.

And my god, the M12 thread has come out nicely - my first threading in steel:

It looks as if it should fit and function:

Now to flip it around and machine up the other side:

Light cuts because it's fairly slender and has a long overhang.

Came out nicely.

Alongside the leadscrew / splined drive shaft it replaces:

Looks good to me. Now over to The Shiz (via Fusion 360) for spline machining....