Once the belt speed calculator tells you your machine’s SFPM, this chart says where to set it. Ranges assume a common direct-drive setup (3-4 inch drive wheel, 1750 RPM motor, VFD) — percentages refer to that machine’s full speed of roughly 1,400-1,800 SFPM.
| Task | SFPM range | VFD feel | Notes |
|---|---|---|---|
| Hogging annealed steel, fresh coarse ceramic | 1,400–1,800+ | Full speed | Sharp belts + speed = cool fast cutting; slow hogging glazes belts |
| General bevel grinding, annealed | 1,000–1,500 | 60–90% | The everyday zone; drop speed as stock thins |
| Hardened steel, shaping | 700–1,200 | 40–70% | Temper protection begins at the dial – see the burned-edge guide |
| Hardened thin edges, tips, finish passes | 400–800 | 25–45% | Feather pressure, dunk cadence, fresh fine ceramics |
| Finishing belts (Trizact class), satin work | 500–900 | 30–50% | Structured abrasives cut cleanest in the slow-middle |
| Wood handles | 600–1,200 | 35–70% | Faster burns resin woods; sand with the grain last |
| Micarta / G10 / synthetics | 400–900 | 25–50% | Heat is the enemy – resins smear and stink past it (respirator regardless) |
| Leather edge sanding & burnishing | 200–500 | Lowest useful | Worn fine belts only; speed tears fiber – see Edges & Finishes |
| Powered stropping (charged leather belt) | 300–600 | Lowest useful | Edge trailing, absolute attention – the strop guide’s rules at machine speed |
Reading the chart honestly
These are working ranges, not laws — belt type, pressure and steel move them. The pattern to internalize: speed suits soft steel and sharp coarse belts; hardness, thinness and finish all push the dial down. A fixed-speed machine lives around the general-grinding zone and improvises the rest, which is the honest argument for variable speed — the VFD combo exists because this chart does.
Browse more tools in the Calculators section.