SO3: Machine Steel And/Or Hardened?

Ordered an S3. Will be here Tuesday.

Primary focus will be on aluminum, but I would like to know if the S3 can handle steel, even hardened steel at all. Either if I go super slowly or with a different spindle or?

The hardened work is pretty small, about the size of your thumbnail, so taking one’s time with it is no big deal. Just want to know if it’s possible at all.


An SO3 is not “aimed” for Ferrous metals.

Ferrous metals require precise RPM knowledge (a spindle with serious power), good feeds and speeds, solid fixturing, and lubrication.

Al and Al alloy can be machined dry on small machines via judicious the use of single flute end mills (see Onsrud) and/or ZrN/TiB2 coated end mills… but lubrication helps.

For steel I would use AlTiN coated end mills.

@WillAdams can comment more, but before attempting serious metals I would consider an option to stiffen the SO3, have a (metal) sea-of-holes bed, add drip lubrication, and use high quality machine tools.


You’re pretty much going to have to have a metal bed.

I’d recommend a solid metal fixture to hold the work-piece in place and all-metal clamping (a bunch of affordable step clamp sets have been linked in various forums recently).

That said, while it sort of works, you have to take into account the fact that you’re not using the tool, esp. the endmill, as intended and the endmill will have a short life — even if you only need one or two, it’ll probably be more affordable to have this done on a real mill. (Or make a set of fixtures and jigs which will allow you to do the work w/ files and a drill press.)

These will work with any 10-32, M5, or M6 sea-of-holes… not just the Nomad.


For a contrasting (and far more successful / optimistic) take on this, see:

It’s been a while but while I was browsing around youtube for SO3 stuff I found a guy who machines steel with an X-carve which is basically the same as a SO3 except with less stepper motor power and less rigidity.
Here is one of his videos. He has a couple more like this and I’m guessing it should be easily achievable given the same parameters.

While my shoulder heals (Torn Rotator Cuff surgery), I have been busy programming the 38 machined parts for this project (Below).

(36 of the parts will be mild steel), BUT:

Changes to the base machine:
Metal (aluminum) base.
I have beefed up my Z axis motor plate,
Wider belts (X & Y)
Makita RT0701 router for the spindle (10,000-30000 rpm, and at the low end, it gets me into the correct SFM for 1/4"carbide end mills)
Mist Coolant system

Do you know the hardness of the metal? Rockwell C (HRc)? I have cut some 38-40 HRc with a 1/8 coated end mill with DOC 0.010" and 6 in feed rate and all went well. The Small project only took about 15 min of machining.

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