Guided by YBmetal, tooling for cast iron: gray/grey & ductile iron castings with in-house machining, simulation-led gating, and traceable QA.
Excerpt: Choosing tooling for cast iron means picking the right inserts, setting realistic speeds/feeds, and using a coolant strategy that balances tool life, finish and dust control. Use the copy-paste tables below for gray vs ductile iron, plus drawing/RFQ notes.
Table of contents
- Insert choices for cast iron (grades, edge prep, breakers)
- Speeds & feeds — gray vs ductile iron (turn/mill/drill)
- Coolant strategy — dry, MQL or flood?
- Finish targets, nose radius & stability tips
- Tool life monitoring & SPC
- Drawing & RFQ notes（copy-paste）
- FAQs
Insert choices for cast iron
Table A — Insert type vs use case（cast iron）
| Use case | Grade & coating | Edge prep | Notes |
|---|---|---|---|
| Gray iron roughing | K20–K30 CVD-coated carbide (TiCN/Al2O3/TiN) | Honed edge, small T-land | Handles abrasive flakes; high speed capable |
| Gray iron finishing | K10–K20 fine-grain carbide, CVD/CVD+PVD | Light hone or sharp w/ small radius | Achieve Ra 1.6–3.2 μm (63–125 μin) |
| Ductile iron roughing | K20–K30 CVD carbide | Honed edge; tougher breaker | Graphite nodules = more ductile cut; avoid built-up edge |
| Ductile iron finishing | K15–K25 PVD-coated (TiAlN/AlTiN) | Microhone | Lower speed than gray; focus on stability |
| Hard/Chilled spots (>45 HRC) | CBN (PCBN) | Chamfered | For local chilled skin/hard inserts; shallow DOC |
| High-speed gray iron milling | Ceramic (SiAlON/whisker) | — | Dry only; rigid setup; for stable walls & constant engagement |
Speeds & feeds（indicative ranges）
Start here, then tune by wear/finish. Units in m/min & sfm; feeds in mm/rev (ipr) for turning and mm/tooth (ipt) for milling.
Table B — Turning (carbide)
| Material & hardness | Cutting speed | Feed (finish → rough) | DOC (finish → rough) |
|---|---|---|---|
| Gray iron HB 170–220 | 120–210 m/min (400–700 sfm) | 0.08–0.20 mm/rev (0.003–0.008 ipr) | 0.3–2.5 mm (0.012–0.10 in) |
| Ductile iron HB 170–240 | 75–150 m/min (250–500 sfm) | 0.10–0.25 mm/rev (0.004–0.010 ipr) | 0.3–2.0 mm (0.012–0.08 in) |
| Chilled spot (CBN) | 60–120 m/min (200–400 sfm) | 0.05–0.15 mm/rev (0.002–0.006 ipr) | 0.1–0.5 mm (0.004–0.020 in) |
Table C — Face/End Milling (carbide unless noted)
| Material | Cutting speed | Feed per tooth | Axial DOC | Radial WOC |
|---|---|---|---|---|
| Gray iron | 180–300 m/min (600–1000 sfm) | 0.05–0.12 mm/zt (0.002–0.005 ipt) | 0.5–2.0 mm | 30–70% D |
| Ductile iron | 120–240 m/min (400–800 sfm) | 0.04–0.10 mm/zt (0.0015–0.004 ipt) | 0.5–1.5 mm | 30–60% D |
| Gray iron (ceramic, dry) | 450–900 m/min (1500–3000 sfm) | 0.05–0.10 mm/zt | Light | 20–40% D |
Table D — Drilling (carbide)
| Hole Ø | Gray iron speed | Ductile iron speed | Feed (ipr) |
|---|---|---|---|
| ≤10 mm (≤0.39 in) | 60–120 m/min (200–400 sfm) | 45–90 m/min (150–300 sfm) | 0.03–0.08 |
| 10–20 mm (0.39–0.79 in) | 45–90 m/min (150–300 sfm) | 35–75 m/min (120–250 sfm) | 0.06–0.15 |
| >20 mm (>0.79 in) | 35–75 m/min (120–250 sfm) | 30–60 m/min (100–200 sfm) | 0.10–0.25 |
RPM quick calc
- Metric:
rpm = (1000 × m/min) / (π × D_mm) - Imperial:
rpm = (sfm × 12) / (π × D_in)
Coolant strategy — dry, MQL or flood?
Indicative shop ranges; confirm with your foundry/heat treater for your section size and chemistry.
Table E — What to use & why（cast iron）
| Scenario | Gray iron | Ductile iron | Notes |
|---|---|---|---|
| General turning & milling | Dry preferred | Dry or MQL | Flood creates slurry; dry keeps edges hot & sharp |
| Finishing bores/seal faces | MQL or light flood | Flood OK | Improves Ra & chip evac; use 6–10% soluble oil |
| Ceramic milling | Dry only | — | Coolant shocks ceramics → fracture |
| Dust control / EHS | High-flow extraction | Extraction | Graphite dust → use enclosure + vacuum; PPE |
| Tapped/reamed holes | MQL/flood | Flood | Prevent galling; stable size |
Keep coolant off CBN/ceramic; for carbide, prefer dry on gray iron. For ductile, dry/MQL works for roughing; flood helps finish.
Finish targets, nose radius & stability
Table F — Typical finish & nose radius (turning)
| Goal | Nose radius | Notes |
|---|---|---|
| Fine finish | 0.4–0.8 mm (0.016–0.032 in) | Light DOC, higher speed; stable fixturing |
| Balanced | 0.8–1.2 mm (0.032–0.047 in) | Most housings; good for Ra 1.6–3.2 μm |
| Heavy rough | 1.2–1.6 mm (0.047–0.063 in) | Deep DOC + sturdy setup |
Stability tips
- Short stick-out; clamp close.
- Use positive rake for ductile iron to reduce cutting forces.
- For thin walls, split passes (semi-finish → finish) and support with soft jaws or mandrels.
Tool wear & SPC
Table G — Monitor & act
| Wear metric | Finish cut limit | Rough cut limit | What to change |
|---|---|---|---|
| VB flank wear | 0.2–0.3 mm | 0.4–0.6 mm | Lower speed; check dust/coolant; edge prep |
| Notch at DOC line | Visible notch | — | Reduce speed; vary DOC; try tougher grade |
| Built-up edge (ductile) | Any BUE | — | Increase speed slightly; use PVD grade; add MQL |
| Chipping (gray) | Edge pits | — | Reduce feed; bigger radius; ensure rigidity |
Log tool-life (min/edge) by op; aim for stable Cpk ≥ 1.33 on critical dims.
Drawing & RFQ notes（paste-ready）
- Material & hardness: Gray iron ASTM A48 CL35B (HB 187–229) / Ductile ASTM A536 65-45-12 (HB 140–187).
- Stock & finish: Use machining allowance by mass; machined faces Ra 1.6–3.2 μm (63–125 μin) unless noted.
- Tooling: Insert class K for cast iron; finishing nose 0.8–1.2 mm.
- Coolant: Dry/MQL for general cast iron; flood only for finishing bores.
- Inspection: CMM on datums & hole position; surface finish on seal faces; hardness on pads.
- Process: Rough → (heat treat if any) → finish; keep serial-tied inspection pack.
Why YB Metal for machining cast iron
- One roof: green sand/resin / shell + CNC machining
- Proven recipes for gray & ductile iron (inserts, speeds/feeds, coolant)
- CMM + surface finish reports; leak/NDT where required
FAQs
CTA — machine cast iron with proof
YBmetal machines gray/grey & ductile iron castings with insert sets, speeds/feeds, and coolant plans proven on the shop floor. Get data you can defend.