Part 2 of the CNC Machining Mini-Course. Start with Part 1 if you haven't.
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When I ran my machine shop, the two machines I reached for most were a Haas VF-2 vertical mill and a Haas ST-10 lathe. Different machines. Different materials. Different part geometries. Understanding which machine does what — and why — is the foundation of everything else in this series.
Let's break them down.
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The CNC Mill
How It Works
In a mill, the cutting tool spins and the workpiece is stationary (clamped to the table). The spindle — the rotating assembly that holds the tool — moves in X, Y, and Z axes to position the tool and drive it through the material.
- • X axis — left and right
- • Y axis — front and back
- • Z axis — up and down
Modern mills have at least 3 axes. Many have 4 or 5, allowing the workpiece or spindle to tilt and rotate, enabling complex geometries without re-fixturing.
What Mills Make
Mills excel at prismatic parts — parts with flat surfaces, pockets, slots, holes, and contoured profiles. Think:
- • Mounting plates with bolt patterns
- • Mold cavities
- • Housings and enclosures
- • Fixtures and jigs
- • Gearboxes and brackets
- • Aerospace structural components
The Haas VF series is the gold standard in production milling. The VF-2 has a 30" x 16" x 20" work envelope — enough to handle most job shop work. On the smaller end, the Haas Mini Mill (about $40,000 new) and the Tormach 1100M (around $16,000) are excellent entry points.
Vertical vs. Horizontal Mills
Most mills you'll encounter are vertical — the spindle points down. The tool enters the work from above. This is intuitive and works well for the vast majority of jobs.
Horizontal mills have the spindle pointing sideways. This seems awkward until you understand why: horizontal mills are faster for heavy material removal (the chips fall away from the cut naturally) and better for certain geometries. Production shops use them for high-volume work. As a beginner, focus on vertical.
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The CNC Lathe (Turning Center)
How It Works
In a lathe, the relationship inverts: the workpiece spins and the cutting tool is stationary (mounted on a turret that can move in X and Z).
- • Z axis — along the length of the part (the spindle axis)
- • X axis — into the part (controls diameter)
The tool moves in Z to travel along the part's length, and in X to cut to specific diameters. As the part spins and the tool advances, material is removed in a continuous helix — the classic "turning" operation.
What Lathes Make
Lathes make round parts — anything with rotational symmetry. Think:
- • Shafts and axles
- • Bushings and sleeves
- • Threaded fasteners and fittings
- • Valve bodies and stems
- • Pistons and cylinders
- • Pulleys and hubs
The key insight: if a cross-section of the part is a circle at every point along its length, a lathe can probably make it.
Live Tooling
Modern CNC lathes often have live tooling — rotating tools mounted in the turret that allow milling operations (drilling off-center holes, cutting flats, milling slots) to be done on the lathe without moving the part to a mill. This is called turn-mill capability and it's extremely useful for parts that need both turning and milling features.
The Haas ST series (ST-10, ST-20, ST-30) are production lathes found in shops everywhere. Tormach's 15L Slant-PRO lathe is a capable hobby/small-shop option at a fraction of the price.
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Other Machines Worth Knowing
CNC Router
Looks like a mill but designed for softer materials — wood, foam, plastics, PCBs, sheet goods. Routers typically have large work areas (4'x8' is common), high spindle speeds, and less rigidity than a proper mill. They're excellent for sign making, cabinet work, and prototype foam models. Not suited for metal machining.
Horizontal Machining Center (HMC)
Think of an HMC as a horizontal mill on steroids, usually paired with a pallet changer so one part can be loaded while another is being cut. Production workhorses. Not a beginner machine.
EDM (Electrical Discharge Machining)
EDM removes material not with a cutting tool, but with electrical sparks. It can cut hardened steel that would destroy conventional tooling, and can create shapes (like square corners in a deep pocket) that mills simply cannot. Two types: sinker EDM (uses a shaped electrode) and wire EDM (uses a continuously-fed wire). When your machinist says a feature is "EDM'd," now you know.
Multi-Axis Machines (4 and 5-Axis)
Standard mills have 3 axes. Add a rotary axis (A or B) and you have 4-axis. Add two rotary axes and you have 5-axis. Five-axis simultaneous machining can produce complex shapes — turbine blades, impellers, sculpted molds — in a single setup that would require dozens of setups on a 3-axis machine.
Haas's UMC-500 and UMC-750 are their 5-axis universal machining centers. These are not beginner machines, but understanding they exist helps you appreciate the full capability landscape.
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Choosing the Right Machine for the Job
The practical question is always: which machine does this part need?
| Part Feature | Machine |
|---|---|
| Flat surfaces, pockets, profiles | Mill |
| Round / cylindrical shape | Lathe |
| Both (complex parts) | Turn-mill or separate operations |
| Wood, foam, sheet goods | Router |
| Hardened steel, sharp inside corners | EDM |
| Complex sculptural geometry | 5-axis mill |
In my shop, most jobs were clear: bracket → mill, shaft → lathe. Where it got interesting was parts that needed both. That's where having both machines — and understanding how to sequence operations — became valuable.
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A Note on Tormach for Beginners
If you're thinking about getting into CNC at home or in a small space, Tormach is where I'd tell most people to look first.
The Tormach 440 fits on a bench. The 770M and 1100M are floor machines but manageable. They're real machines that can hold real tolerances in aluminum, steel (with care), and plastics. The PathPilot controller is excellent — it has a touchscreen interface that feels more intuitive than old-school Fanuc or Haas controls.
Tormach also has good community support, YouTube content, and documentation. For learning, that matters as much as the machine specs.
Next post, we get into how these machines know where they are — coordinate systems and work offsets. That's where the math starts.
— Dr. Scott