Machining Speeds & Feeds Card
One page. Speeds, chip load and drill feed, imperial and metric.
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Shop-tested RPM, feed, and chip guidance
Get practical starting points for drilling steel, stainless, aluminum, cast iron, plastics, and wood with HSS, cobalt, or carbide bits.
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Quote shop work and check operations against your spindle's top speed.
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Recommended drill and setup tools
Topic-specific picks for drilling speed work, bit life, and hole-quality consistency.
Irwin Cobalt M35 Drill Bit Set (29 pc)
- Wide fractional range for shop work
- Split-point tips reduce walking
- Useful for steel and stainless drilling
Bosch CO14B M42 Cobalt Drill Set
- Heat-resistant cobalt alloy for hard metals
- Three-flat shanks reduce chuck slip
- Good option for stainless-heavy work
WD-40 Specialist Cutting Oil
- Reduces friction and heat at the edge
- Improves tool life on difficult alloys
- Helpful for stainless and deep holes
Starrett Digital Caliper
- Verify bit and hole diameter quickly
- Useful for setup and inspection checks
- Improves repeatability across jobs
Leather Work Gloves
- Protect hands around hot chips and edges
- Better handling when clamping workpieces
- Useful for deburring and post-drill cleanup
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How to use this drill speed calculator
Start by setting your units, then enter drill diameter, material, bit type, machine setup, and hole depth. The calculator returns RPM and feed values based on recovered live tables and shop modifiers. Treat the output as a starting point — chip color, sound, and bit temperature tell you whether to nudge RPM or feed up or down.
Practical workflow
- Use a center punch or spot drill to prevent walking before the main drill engages.
- Run a short test hole in scrap and inspect chip formation before production drilling.
- For holes deeper than 3× diameter, use peck cycles to clear chips and refresh coolant at the tip.
- For stainless and tool steel, use cutting fluid and maintain positive feed so the bit cuts instead of rubs.
- Clamp work securely; hand drills get a built-in speed reduction because rigidity is lower than a press or mill.
Record successful RPM and feed pairs by material and diameter in your shop notebook. Reusing proven settings beats guessing on every new job and extends bit life across the board.
Cutting speed reference table (SFM)
Surface feet per minute (SFM) is the speed at which the cutting edge moves through the material. The calculator converts SFM to RPM using drill diameter: RPM ≈ (SFM × 3.82) ÷ diameter in inches. Smaller drills run faster RPM at the same SFM; larger drills run slower. Tool material matters — cobalt and carbide tolerate higher SFM than plain HSS.
| Material | HSS | Cobalt | Carbide | Notes |
|---|---|---|---|---|
| Mild Steel | 80-100 | 88-110 | 200-300 | Blue chips can be acceptable if cut remains stable. |
| Stainless 304 | 30-50 | 35-55 | 80-150 | Avoid rubbing to prevent work hardening. |
| Stainless 316 | 25-40 | 28-45 | 70-130 | Use sulfurized cutting fluid. |
| Aluminum | 200-300 | 220-330 | 500-800 | Fast speeds with chip evacuation control. |
| Cast Iron | 50-80 | 55-90 | 150-250 | Typically drilled dry. |
Use the table to sanity-check calculator output. If chips are too fine and powdery, you are likely rubbing — increase feed or reduce RPM. If the bit is smoking or blueing, reduce RPM and add coolant. Long-chipping materials like aluminum need aggressive chip evacuation; peck drilling keeps the flutes from packing.
Frequently asked questions
Can I use these speeds on a hand drill?
Yes, but this calculator intentionally reduces speeds for hand drills due to lower rigidity and higher vibration. Clamp the workpiece, use sharp bits, and avoid side load that flexes the drill — flex causes intermittent cutting and work hardening on stainless.
Why does my drill bit burn up quickly?
The most common causes are excessive RPM, insufficient feed pressure, dull or wrong tool material, and no lubrication on materials that require coolant. A burning smell usually means the edge is rubbing, not shearing — lower RPM and push harder with steady pressure.
How do I avoid work hardening in stainless?
Use cobalt or carbide tooling, run conservative RPM from the calculator, apply sulfurized cutting oil, and maintain steady feed so the bit keeps cutting rather than rubbing. Stop immediately if you hear squealing — that is often the start of work hardening ahead of the tip.
Cutting Fluid and Heat Management
Cutting fluid dramatically extends drill bit life by reducing heat and friction at the cutting edge. Heat is what kills edges first — long before you hit the theoretical SFM limit. For mild and medium carbon steel, use cutting oil or sulfurized thread-cutting oil applied at the hole mouth. For aluminum, WD-40, kerosene, or dedicated aluminum tapping fluid improves finish and prevents chip welding to the flutes.
For stainless and tool steel, use heavy-duty cutting fluid and conservative speeds from this calculator. Stainless work-hardens instantly if the bit rubs without cutting — you will hear the change before you see it. Never drill stainless dry in production work. Peck cycles, fresh coolant at each peck, and sharp cobalt bits are the combination that keeps stainless holes on size without destroying tooling.
When Calculated RPM Still Fails — Diagnose or Pick Bits
Bit burn-up, walking on start, poor/oversized holes, breakage, or RPM beyond machine max: Drill Speed Troubleshooting. Bit type and coating (HSS vs cobalt vs carbide, twist vs step): How to Choose Drill Bits for Metal.