Sienci Labs
Sienci AltMill Feeds & Speeds Calculator
Starting feeds and speeds for the Sienci Labs AltMill MK2 4x4, with the numbers already adjusted for its spindle range and frame. Grab a starting point from the chart, then open the live calculator to watch the cut and fine-tune it for your exact bit.
Open the live calculator for the Sienci AltMillDialing in the Sienci AltMill
Two things set the numbers on the Sienci AltMill: how fast the VFD Spindle spins, and how much the frame can take without chattering. It runs a working range of about 6,000 to 24,000 RPM, on ball screws on all axes. The Sienci AltMill is one of the stiffer hobby machines, so it can take deeper passes than most before it starts to chatter.
So for a 1/4" two-flute bit in softwood, a sensible starting point on the Sienci AltMill is around 17,000 RPM and 102 inches per minute, taking about 0.11875" per pass on a slot. The full chart below covers the materials you are most likely to cut. These are conservative starting points: always test on scrap and let your ears do the final tuning.
Sienci AltMill starting feeds and speeds
Two-flute bit, slotting cut (the toughest case for clearing chips). Feed in inches per minute, depth per pass in inches.
| Material | Bit | Spindle RPM | Feed rate | Depth / pass |
|---|---|---|---|---|
| Softwood | 1/8" | 24,000 | 96 ipm | 0.059" |
| 1/4" | 17,000 | 102 ipm | 0.119" | |
| Hardwood | 1/8" | 24,000 | 72 ipm | 0.030" |
| 1/4" | 20,000 | 100 ipm | 0.059" | |
| Plywood / MDF | 1/8" | 24,000 | 96 ipm | 0.059" |
| 1/4" | 17,000 | 102 ipm | 0.119" | |
| Acrylic | 1/8" | 24,000 | 96 ipm | 0.045" |
| 1/4" | 13,000 | 104 ipm | 0.089" | |
| HDPE / Plastics | 1/8" | 17,000 | 102 ipm | 0.045" |
| 1/4" | 10,000 | 100 ipm | 0.089" | |
| Aluminum | 1/8" | 24,000 | 48 ipm | 0.015" |
| 1/4" | 24,000 | 96 ipm | 0.030" |
Numbers are generated by our feeds and speeds calculator using the Sienci AltMill's spindle range and a stout-frame rigidity factor. Aluminum needs a single flute plus lubricant. Always confirm your bit maker's chart and test on scrap.
Want to see it cut?
Open the interactive calculator loaded with the Sienci AltMill. Change your bit and material, watch the cut run live, and hear the difference between a dialed-in cut and a bad one.
Open the Sienci AltMill calculatorSienci AltMill feeds and speeds FAQ
What RPM should I run on a Sienci AltMill?
For most wood with a 1/4" two-flute bit, 17,000 RPM is a good starting point on the Sienci AltMill. Its working range is about 6,000 to 24,000 RPM. Go higher for smaller bits and finer detail, lower for big bits and heavy stock removal.
What feed rate should I use on a Sienci AltMill in hardwood?
Start around 100 inches per minute with a 1/4" two-flute bit in oak or maple on the Sienci AltMill, at roughly 20,000 RPM. Listen to the cut and adjust: clean chips mean you are dialed in, fine dust means you are going too slow.
Can a Sienci AltMill cut aluminum?
Yes. The Sienci AltMill is rigid enough for light aluminum work with a single-flute bit, shallow passes, and plenty of lubricant or air. Keep the chipload small and the depth per pass well under the numbers you would use for wood.
Sienci AltMill full review
Specs, price, and what owners actually say.
CNC chip load chart
Feed-per-tooth for every bit and material.
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