Drilling Stainless Steel: Tools and Parameters That Work

Stainless drilling fails more often than any other operation. Work-hardening, low thermal conductivity, and gummy chips destroy drills. Here is what works.

Stainless Steel Categories

• Austenitic (304, 316) — Most common, easiest stainless to drill (still tough)
• Ferritic (430) — Easier than austenitic
• Martensitic (410, 420) — Hardenable, hardest to drill when treated
• Precipitation hardening (17-4 PH) — Aerospace standard, tough
• Duplex (2205) — Most challenging, work-hardens dramatically

Drill Selection

Cutting Parameters

For 12mm carbide through-coolant drill in 304 stainless:

• Vc: 50-70 m/min (1,300-1,860 RPM)
• Feed: 0.15-0.20 mm/rev
• Coolant: through-tool at 70+ bar
• Peck cycle: not needed if internal coolant working

Common Mistakes

1. Speed Too High

Stainless work-hardens at high temperature. Reducing speed often INCREASES tool life.

2. Insufficient Feed

Below 0.10 mm/rev, drill rubs and work-hardens stainless. Damages drill within seconds.

3. No Through-Coolant

External coolant cannot reach cutting edge in stainless. Heat builds rapidly.

4. Wrong Coating

TiN coating welds with stainless. AlTiN or AlCrN required.

5. Letting Drill Wear Past 60% Life

A worn drill in stainless work-hardens the hole, then breaks. Index frequently.

Best Practices

• Drill straight through if possible (no peck cycles in stainless)
• Maintain coolant flow throughout cycle
• Inspect drill every 50-100 holes
• Replace at 80% expected life, not at failure
• For deep holes, use double-margin or carbide-tipped specialized drills

Tool Recommendations

• Sandvik CoroDrill 460-MM grade
• Walter A3782 with through-coolant
• OSG ADO-SUS specifically for stainless
• Mitsubishi MWS-SUS

See our HP coolant guide (similar principles for stainless).