For carbide drilling, calculate rpm from cutting speed and drill diameter first, then calculate feed rate from rpm and feed per revolution. After that, adjust the numbers for material, coolant, hole depth, runout, and machine rigidity.
The rpm formula
The common metric formula is:
n = 1000 x Vc / (pi x D)
Here, n is spindle speed in rpm, Vc is cutting speed in m/min, and D is drill diameter in mm. A 10.7 mm drill at 70 m/min gives a starting speed close to 2080 rpm. Shops often round this to a practical machine setting and then test chip shape, sound, and load.
The feed rate formula
After rpm is selected, calculate feed rate:
F = n x fn
Here, F is feed rate in mm/min and fn is feed per revolution in mm/rev. If the speed is 2000 rpm and the starting feed per revolution is 0.20 mm/rev, the feed rate is 400 mm/min.
Why the formula is only the starting point
Cutting data is not universal. Stainless steel, titanium, hardened steel, cast aluminum, ductile iron, and low-carbon steel all behave differently. A stable through-coolant setup can often use a different starting point than an external-coolant setup with poor chip evacuation. A deep hole also needs more attention than a shallow one.
- Reduce cutting speed if heat, noise, or flank wear rises quickly.
- Reduce feed if the drill pushes, chips pack, or hole size drifts.
- Increase feed carefully if rubbing creates heat and poor chip shape.
- Check runout before blaming the cutting data.
What to send for a drilling review
For a stable recommendation, provide drill diameter, hole depth, material grade, hardness, coolant type, coolant pressure, current speed, feed, chip shape, and the problem you are seeing. HEYI can review this against a through-coolant carbide drill or another drilling route. You can also use the cutting parameter calculator as a first check, then submit the real shop data through the RFQ page.