Bob's CNC KL744

About the Machine

The KL744 is BobsCNC's largest kit, with a 1219 x 1219 x 127 mm working area and 114 mm of gantry clearance. It drives X and Y on a steel-reinforced Bell-Everman servo system with NEMA 23 closed-loop servo steppers (425 oz-in / 3 Nm holding torque), a ball screw on Z, and ships with a Makita RT0701C router rated 10,000 to 30,000 RPM. It runs GRBL 1.1 firmware on an Uno controller.

Cut Settings on this Machine

Every cut starts with one formula: Feed Rate = Spindle Speed (RPM) x Chip Load x Number of Cutting Edges (flutes). Chip load is the thickness of material each cutting edge removes in one revolution of the bit. This number comes from the manufacturer of the bit, which publishes a chip-load chart for each bit diameter and material. Look up your exact bit and material, start from the middle of the published range, and you have the third number in the formula. The chart below shows the recommended spindle speed for each material and bit type.

The KL744's Makita RT0701C router runs from 10,000 to 30,000 RPM, comfortably above every speed on the chart, so you can run the chart's recommended RPM directly instead of capping it. It pairs closed-loop NEMA 23 servo steppers and a steel-reinforced Bell-Everman drive on X/Y with a ball screw on Z, a much stiffer build than a belt-and-acme-rod kit, even at this larger 1219 x 1219 mm bed size. A truly rigid machine with a powerful spindle can cut as deep as the bit is wide in a single pass, but that takes real spindle torque, a drive train and clamps that hold firm, a gantry that will not flex, and enough mass to soak up vibration. The KL744's closed-loop servos and ball-screw Z put it closer to that bar than a lighter kit, but it is still a hobby machine, not a production mill, so build up to full-diameter passes gradually rather than assuming it from day one. The fastest way to dial in a cut is to see what has already worked for other people.

Worked example for feed rate: 1/8in (3.175mm) two-flute solid carbide end mill in hard wood. The chart says 16,000 RPM, and this router's 10,000 to 30,000 RPM range covers that easily, so run 16,000. With the bit maker's 0.025mm per tooth (0.0010 in): 16,000 x 0.025 x 2 = 800 mm/min (31 in/min) feed. For depth per pass, start shallow and check Community Cut Settings in Easel for what works on this machine. If the cut sounds strained, reduce the depth, not the feed. Slowing the feed below the chip load makes the bit rub instead of cut.

Community Cut Settings shows the spindle speed, feed rate, and depth per pass other makers actually run for your machine, material, and bit.