Calculate spindle RPM, feed rate, feed per revolution, cutting speed, material removal rate and turning time for CNC lathe operations.
Add stock diameter, final diameter and turning length to estimate radial stock removal, axial cutting distance and approximate cutting time.
| Material | Carbide | Cermet | HSS | Ceramic |
|---|---|---|---|---|
| Mild steel | 150 | 180 | 25 | 300 |
| Carbon steel | 120 | 150 | 20 | 250 |
| Alloy steel | 100 | 130 | 15 | 220 |
| Stainless steel | 80 | 100 | 12 | 180 |
| Tool steel | 70 | 90 | 12 | 160 |
| Cast iron | 120 | 150 | 20 | 250 |
| Aluminum | 300 | 350 | 80 | 500 |
| Brass | 250 | 300 | 70 | 450 |
| Bronze | 120 | 150 | 30 | 250 |
| Copper | 200 | 250 | 50 | 350 |
| Titanium alloy | 50 | 60 | 8 | 100 |
| Nickel alloy | 40 | 50 | 6 | 80 |
| Magnesium alloy | 350 | 400 | 100 | 600 |
| Engineering plastic | 250 | 300 | 100 | 450 |
| Operation | Light / finish | General | Heavy roughing |
|---|---|---|---|
| Small diameter <20 mm | 0.05 | 0.10 | 0.18 |
| 20–40 mm | 0.08 | 0.15 | 0.25 |
| 40–60 mm | 0.10 | 0.20 | 0.30 |
| 60–100 mm | 0.12 | 0.25 | 0.40 |
| 100–150 mm | 0.15 | 0.30 | 0.50 |
| 150+ mm | 0.18 | 0.35 | 0.60 |
Feed values are generalized starting points. Insert nose radius, chip breaker, depth of cut, material and machine capability can substantially change the recommended feed.
How do I calculate CNC turning RPM? RPM = 1000 × cutting speed ÷ (π × cutting diameter in mm).
How do I calculate turning feed rate? Multiply spindle RPM by feed per revolution. For example, 1,000 RPM × 0.20 mm/rev = 200 mm/min.
What is feed per revolution? It is the distance the tool advances for each spindle revolution, normally expressed in mm/rev.
Why does diameter affect RPM? At the same cutting speed, a larger diameter travels farther during each revolution, so the spindle must turn more slowly.
What is CSS in CNC turning? Constant surface speed automatically changes spindle RPM as the cutting diameter changes so the programmed cutting speed stays approximately constant.
Should I use the same cutting speed for every steel? No. Alloy, hardness, heat treatment and insert grade can substantially change recommended cutting conditions.
Does insert nose radius affect feed? Yes. Nose radius, insert geometry and desired surface finish influence suitable feed per revolution.
Can this calculator determine exact CNC G-code? No. It calculates machining parameters only. CNC programming also depends on the machine control, toolpath, workholding, coordinate system and operation.
Can I use this for facing? Yes, the calculator can estimate parameters using the current cutting diameter. During actual facing, the diameter changes continuously toward the center.
Are the material values exact? No. They are generalized starting references. Manufacturer cutting data for the exact insert and material should take priority.