Case Study: Reducing Wear Costs by Switching to Coated SPMT Inserts

When your shop fights rapid wear on steel and stainless jobs, it’s tempting to keep swapping the same uncoated inserts and push through. This case study shows why a coated SPMT is often the smarter move—backed by numbers, simple math, and practices consistent with ISO material-group guidance used across major tooling catalogs.

---

Company profile and pain point

• Industry: Tier-2 automotive supplier

• Jobs: General turning/facing on alloy steel (ISO P) with occasional austenitic stainless (ISO M)

• Problem: Unpredictable tool life; frequent stoppages to index inserts; rising tool cost per part and overtime

Baseline setup

• Insert: SPMT120408, uncoated, general-purpose geometry

• Edge life: ~20 min/edge on steel

• Index time: 2 min per edge

• Cycle time: 3 min/part

• Machine cost rate: $60/hour

• Insert price: $6/insert (4 edges)

Intervention

• Switched to SPMT120408 –MP, PVD TiAlN-coated on a medium-tough substrate (balanced for steels; acceptable for occasional stainless).

---

Results you can audit (one 1,000-part order)

Edge life & edges used

• Uncoated: 20 min/edge → ~6.67 parts per edge → ≈150 edges for 1,000 parts

• Coated: 45 min/edge → 15 parts per edge → ≈66.7 edges

Insert spend

• Uncoated: 150 edges ÷ 4 edges/insert ≈ 38 inserts → $228

• Coated: 66.7 edges ÷ 4 ≈ 17 inserts → $136
  Insert savings: $92

Downtime cost (indexing only)

• Uncoated: 150 edges × 2 min = 300 min (5.0 h) → $300

• Coated: 66.7 edges × 2 min = 133.3 min (2.22 h) → $133
  Downtime savings: $167

Total savings for the order

• $92 (inserts) + $167 (downtime) = $259 saved

• Per-part saving: ~$0.26

• Throughput gain: indexing time drops from 5.0 h to 2.22 h; total job time falls from ~55.0 h to ~52.2 h (≈5% faster end-to-end)

Why this happens: PVD TiAlN improves hot hardness and oxidation resistance; medium-positive chip geometry maintains chip thickness and evacuation, reducing flank wear and edge chipping—principles that align with ISO 513 material groups and widely published manufacturer guidance on coated vs. uncoated carbide behavior.

---

Wear patterns: before vs after

• Before (uncoated): rapid flank wear and occasional micro-chipping on interrupted cuts; long, hot chips at low feeds.

• After (PVD coated): slower uniform flank wear; chips curled and broke consistently within the –MP feed window; stable dimensions over longer runs.

---

Parameter adjustments that made the switch work

1. Stayed in the chipbreaker’s feed window to avoid rubbing (slightly increased fn on finishing passes).

2. Reduced surface speed ~8–10% on stainless to control heat, then optimized upward for steel.

3. Aimed coolant directly at the rake; flow kept steady to carry chips and protect the coating.

4. Kept nose radius modest (0.4 mm) on thin-wall features; used 0.8 mm for roughing/scale.

---

What this means for your shop

• If you’re indexing more than every 20–25 minutes on steels, a PVD-coated SPMT with a medium-positive breaker is a strong first trial.

• Track parts per edge and indexing time; savings usually come from both insert life and fewer stoppages.

• Even if a coated insert costs more per piece, overall cost per part tends to drop due to longer edge life and reduced unplanned downtime.

---

Product recommendation (Get a Quote)

SPMT120408 –MP, PVD TiAlN grade — balanced toughness and heat resistance for ISO P jobs with occasional ISO M work.

---

Why you can trust this approach

• ISO 513 material groups underpin grade/geometry selection (P/M/K).

• PVD TiAlN coatings are widely documented to improve hot hardness and oxidation resistance, enabling longer life at moderate-to-high temperatures, especially in steels and many stainless applications.

• Medium-positive chipbreakers are standard recommendations for general steel turning to balance cutting force, chip curl, and edge strength.