Calculate saw blade speed (RPM), cutting speed (SFM), feed rate (IPM), and chip load for circular, cold, and band saw blades.
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Saw Speed and Feed Formula
The blade speed (RPM) is found from the cutting speed and blade diameter:
RPM = (SFM x 12) / (pi x D)
The cutting speed (SFM) is found from the blade diameter and blade speed:
SFM = (pi x D x RPM) / 12
The feed rate (IPM) is found from the blade speed, tooth count, and chip load:
IPM = RPM x T x CL
The chip load per tooth is found by rearranging the feed rate equation:
CL = IPM / (RPM x T)
Where:
RPM is the blade or spindle speed in revolutions per minute. SFM is the cutting (surface) speed in surface feet per minute. D is the blade diameter in inches. T is the number of teeth on the blade. CL is the chip load, the thickness of material removed by each tooth in inches. IPM is the feed rate in inches per minute.
Use SFM to match the blade material and the workpiece, convert it to RPM for your blade diameter, then set the feed rate so each tooth removes a safe chip load.
Typical Cutting Speeds and Chip Loads
The values below are common starting points. Always check your blade and machine manufacturer ratings before cutting.
| Workpiece Material | Cutting Speed (SFM) |
|---|---|
| Aluminum | 600 to 3000 |
| Mild steel | 80 to 150 |
| Stainless steel | 60 to 120 |
| Hardwood | 2000 to 9000 |
| Softwood | 3000 to 12000 |
| Blade Diameter (in) | Typical Chip Load (in/tooth) |
|---|---|
| Under 4 | 0.004 to 0.008 |
| 4 to 8 | 0.008 to 0.015 |
| 10 to 12 | 0.015 to 0.025 |
Example Problems
Example 1. You are cutting aluminum with a 10 inch circular saw blade and want a cutting speed of 2000 SFM. Find the blade speed.
RPM = (2000 x 12) / (3.1416 x 10) = 24000 / 31.416 = 763.9 RPM.
Example 2. The blade above runs at 764 RPM, has 60 teeth, and a chip load of 0.010 inches per tooth. Find the feed rate.
IPM = 764 x 60 x 0.010 = 458.4 inches per minute.
FAQ
What is the difference between SFM and RPM? SFM is the speed at the cutting edge measured in surface feet per minute, which depends on the material being cut. RPM is how fast the blade spins, which depends on both the SFM you want and the blade diameter.
What is chip load? Chip load is the thickness of material each tooth removes in a single pass, measured in inches per tooth. Too low a chip load causes rubbing and heat, while too high a chip load overloads the teeth.
Does this work for both band saws and circular saws? The RPM, SFM, and feed rate relationships apply to circular and cold saw blades by diameter. Band saws are usually rated directly in surface feet per minute, so you can use the SFM value as the band speed and the feed rate equation for inches per minute.