Bob's CNC and Affordable Woodworking: What the Machine Can Actually Cut

A Bob's CNC machine sits in a different class from a production mill. The frame is usually aluminum extrusion or welded steel tube, the motion comes from belt or lead screw drives on linear rails, and the spindle is a trim router or a small air-cooled unit. That construction keeps the price low. It also sets the ceiling on how hard you can push a cut.

The trade-off is not mysterious. A light frame deflects under cutting load. So does a long unsupported gantry. When the tool pushes into hardwood, the frame bends a few thousandths, the cutter grabs, and the edge finish suffers.

None of that makes the machine bad. It means you match the cut to the structure. Shallow depth of cut, moderate feed, sharp tooling, and a workpiece that is firmly clamped will produce clean parts all day on a machine in this class.

The working area is the first number to check against your part. A benchtop router may give you a cutting area around 600 × 600 mm, while larger kits reach roughly 1,200 × 2,400 mm for full sheet goods. Those figures describe travel, not the size of part you can hold. Clamps, tabs, and fixture plates eat into the edges.

Z travel matters just as much as X and Y. If you plan to cut a thick butcher block or a deep 3D relief, the gantry clearance and spindle travel set the limit. A machine with 100 mm of Z travel cannot carve a 150 mm tall shape, no matter how large the bed is.

Think about how you will load the sheet too. A machine that needs a full 4 × 8 ft panel lifted onto the bed is a two-person job in a small shop. Many owners cut panels down first on a track saw, then run smaller blanks on the router. That keeps the machine useful without demanding a large infeed area.

For long parts, plan the tiling strategy before you buy. Indexing pins and a repeatable home position let you machine a long rail in two setups. Without that, you are limited to the bed length in front of you.

Wood and wood products are the natural home for this machine class. Plywood, MDF, hardwoods, and softwoods all machine predictably at moderate feeds. MDF is abrasive and dulls tooling fast, but it holds detail well and costs little. Hardwood needs sharper tooling and lighter passes.

Plastics behave differently. Acrylic chips and can weld back into the cut if the feed is too slow. HDPE and POM cut cleanly with a single-flute cutter and good chip evacuation. ABS is forgiving. Carbon fiber is a different problem: the dust is abrasive and a health hazard, so it needs extraction and a respirator, and it wears cutters quickly.

Soft metals are possible but limited. Aluminum sheet and thin plate can be machined with a small cutter, light depth of cut, and a mist of lubricant. Deep pockets in aluminum on a light frame usually chatter. If your part is mostly aluminum with tight tolerances, this is the point where the job stops being affordable woodworking and becomes precision machining work.

A quick test before you commit: cut a scrap of the actual material at the actual depth. If the finish is fuzzy or the machine shakes, reduce the load or change the tool. Do not chase the problem with more spindle speed.

Workholding decides the finish more often than the spindle does. A part that lifts or vibrates will produce a rough edge no matter what tool you run. Double-sided tape works for thin panels. Cam clamps and screw-down tabs work for solid stock. A spoilboard with a grid of threaded inserts lets you position clamps anywhere without drilling into the bed.

Feeds and speeds on a light machine follow one rule: keep the chip load steady and the load light. A chipload around 0.1 mm per tooth on a two-flute cutter in plywood is a common starting point. Increase feed before you increase depth. A cutter that rubs instead of cuts heats up, dulls, and burns the wood.

Climb milling usually gives a better edge on a machine with backlash in the drive, because the cutter pulls the material toward the tool rather than pushing it away. Test both directions on scrap. The difference shows up most on cross-grain cuts in hardwood.

Leave a finishing pass. Rough out the shape with a 0.3 mm allowance, then take a full-depth finishing pass at the final dimension. The edge quality improves more from that single step than from any change to spindle speed.

Dust and chip evacuation are part of the cut, not cleanup. Chips left in the kerf get re-cut, which dulls the tool and burns the edge. A dust shoe and a shop vacuum handle most wood jobs. Plastics and metals need different collection.

There is a clear line where a low-cost router stops being the right tool. It is not about the material name. It is about the tolerance and the geometry. If a part needs ±0.05 mm across a feature, or if it has undercuts, deep pockets, or features on five faces, a light three-axis router cannot hold it.

The second signal is volume. A machine that cuts one part well may still lose money on a run of 500, because setup and manual loading dominate the cycle. Production work needs fixtures, tool changers, and a machine that holds tolerance after eight hours of cutting.

That handoff is where we work. GreatLight runs 127 high-precision CNC machines, including 16 simultaneous 5-axis machining centers, with a maximum processing size of 4,000 mm. We hold ±0.005 mm and finish down to Ra 0.2–0.8 μm when the drawing calls for it.

The practical split looks like this: prototype and low-volume wood or plastic parts stay on the router; metal parts with real tolerances, or any part headed for a production run, come to us. We quote and return a free DFM analysis within 12 hours, and production can start within 24 hours. Parts ship in 3–5 days.

We keep no minimum order quantity, so a single prototype is fine. Uploads are secure and confidential, and an NDA is available on request.