How to Calculate Feed Rate for Drilling
Calculating the correct feed rate for drilling is crucial for achieving efficient material removal, extending tool life, and ensuring good hole quality. The feed rate, often expressed in inches per revolution (IPR) or millimeters per revolution (mm/rev), dictates how fast the drill bit advances into the workpiece with each rotation.
Factors Affecting Feed Rate:
- Drill Diameter: Larger diameter drills generally require higher feed rates.
- Material Being Drilled: Softer materials can typically be drilled at higher feed rates than harder materials.
- Drill Material and Geometry: The type of steel (HSS, Cobalt), coatings, and the drill's point angle influence the optimal feed.
- Machine Spindle Speed (RPM): The feed rate is directly related to the spindle speed.
- Lubrication/Cooling: Proper coolant flow can allow for more aggressive machining parameters.
- Depth of Hole: Deeper holes may require adjustments to chip evacuation, potentially affecting feed.
The Formula:
While complex charts and software exist, a common starting point for calculating feed rate (f) in inches per revolution (IPR) is by using a recommended chip thickness (t) based on the drill diameter (D). A widely used formula relates these variables:
f = t * D
Where:
- f = Feed Rate (IPR)
- t = Recommended Chip Thickness (IPR) – This value is material and drill-dependent and is often found in machining handbooks or manufacturer data. Common values for steel might range from 0.002 to 0.010 IPR for smaller drills.
- D = Drill Diameter (inches)
If you are working in metric units, the formula remains conceptually the same but uses millimeters:
f = t * D
Where:
- f = Feed Rate (mm/rev)
- t = Recommended Chip Thickness (mm/rev) – Typical values for steel might range from 0.05 to 0.25 mm/rev.
- D = Drill Diameter (mm)
Using the Calculator:
This calculator helps you estimate the feed rate. You'll need to know the drill diameter and a recommended chip thickness for the material you are drilling. Consult your tooling manufacturer's recommendations or a machining handbook for precise chip thickness values for your specific application.