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Grinding Speeds and Feeds
Guide · Updated October 28, 2026
In grinding the wheel does the cutting, so speed is wheel surface feet per minute (SFPM). Most vitrified wheels run around 5,500–6,500 SFPM, and you never exceed the maximum RPM printed on the wheel blotter.
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Step by step
- Read the wheel label: Note the wheel diameter, bond and the maximum safe RPM on the blotter.
- Check spindle RPM: Confirm the spindle RPM is at or below the wheel maximum. Never mount a wheel rated below the spindle speed.
- Calculate SFPM: SFPM = RPM × π × diameter (in) ÷ 12. Recheck as the wheel wears smaller.
- Ring test and guard: Ring-test vitrified wheels before mounting, use blotters, and keep the guard on. Stand aside on startup.
- Dress the wheel: True and dress with a diamond so the wheel cuts freely and runs round.
- Set downfeed and crossfeed: Rough about 0.0005–0.001 in per pass, finish 0.0001–0.0002 in, and crossfeed about 1/4 to 1/3 of the wheel width per stroke for roughing, less for finishing.
Worked example
A 7 in wheel on a 3,450 RPM surface grinder: SFPM = 3,450 × 3.1416 × 7 ÷ 12 ≈ 6,323 SFPM. The blotter is marked 3,600 RPM max, so it is safe.
Grinding 0.005 in off a hardened 1 in wide block: rough 8 passes at 0.0005 in (0.004 in), dress lightly, then finish 5 passes at 0.0002 in, with a final spark-out pass. Crossfeed about 0.125 in per stroke on a 1/2 in wide wheel when roughing.
Cylindrical grinding work speed
On a cylindrical or tool post grinder the work turns slowly against the wheel: roughly 70–100 SFM work speed is a common starting point. For a 2 in part that is about 70 × 3.82 ÷ 2 ≈ 134 RPM. The wheel stays around 6,000 SFPM.
Tips
- Wheel safety comes first: wear eye protection and never stand in line with the wheel on startup.
- Coolant controls heat, burn and size growth: cutting fluid and coolant basics.
- Finish depends on dressing, grit and spark-out passes: surface finish basics.
- Let parts cool before measuring: ground parts grow with heat. See temperature compensation.
- Other speeds families: turning and milling.
FAQ
What speed should a grinding wheel run?
Most vitrified wheels run about 5,500–6,500 SFPM, and never above the maximum RPM marked on the wheel.
How do you calculate grinding wheel SFPM?
SFPM = RPM × π × diameter in inches ÷ 12. A 7 in wheel at 3,450 RPM is about 6,323 SFPM.
How much downfeed on a surface grinder?
Roughly 0.0005–0.001 in per pass roughing and 0.0001–0.0002 in finishing, followed by a spark-out pass.
Why is my part burning when grinding?
The wheel is loaded or glazed, too hard, or the downfeed is too heavy. Dress the wheel, use coolant and lighten the cut.
Is there a free gage block calculator?
Yes. The Gage Block Calculator at gageblockcalc.com builds any stack, free with no login.
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General shop information only — follow your tooling, machine and gage manufacturers' instructions and your quality system.