Engineering · Machining guide
How to machine bronze C932 (SAE 660).
C932 (also called SAE 660) is the leaded tin bronze that’s the workhorse for sleeve bearings, bushings, and wear surfaces. The lead-tin-copper combination gives self-lubricating properties and good machinability — easier than pure copper but still gummy compared to steel. Standard practice: sharp tools, coolant flood, focus on surface finish for sliding-wear applications.
01 · Cutting parameters
Numbers that work.
| Operation | Tool | SFM | IPT / IPR |
|---|---|---|---|
| Roughing turn | Uncoated carbide | 300–500 | 0.010–0.020 IPR |
| Finishing turn | Uncoated carbide | 500–700 | 0.005–0.010 IPR |
| End mill (rough) | Solid carbide | 300–450 | 0.004–0.008 IPT |
| End mill (finish) | Solid carbide | 450–600 | 0.002–0.005 IPT |
| Drilling | HSS or carbide | 100–200 | 0.005–0.010 IPR |
| Tapping | HSS | 40–80 | — |
| Boring (bushings) | Uncoated carbide | 400–600 | 0.003–0.007 IPR |
IPT (chip-load) values assume roughly ½–1″ end mills; scale down for smaller tools — see the chip-load chart.
02 · Practical notes
Bushings get all the attention.
- Tooling: uncoated polished carbide. Sharp positive-rake geometry. Avoid coatings — they encourage chip welding on copper-base alloys.
- Coolant: water-soluble flood. C932 is forgiving on coolant choice — emulsion at 6–10% works fine.
- Surface finish for bearing surfaces: 32 µin Ra is the typical bearing spec. Achievable with standard sharp tooling. For high-load or low-speed applications, 16 µin Ra requires PCD or polished carbide finishing.
- ID concentricity: bushing applications need tight ID/OD concentricity (often ±0.0005″ or better). Bore-and-turn from the same chucking; don’t re-fixture between operations.
- Press-fit allowance: standard press-fit interference for bushings is 0.0008–0.0015″ per inch of OD. Plan for the mating-housing dimension first, then size the bushing OD.
- Lead content: C932 has ~7% lead. Same restrictions as C360 brass for medical, food-contact, and lead-restricted applications. Lead-free bearing alternatives (C90300 tin bronze) exist with slightly different machining.
Keep exploring
Related tools & references
SAE 660 bearing bronze properties and specs.
Set SFM and feed for sliding-wear finish work.
Per-tooth chip loads for leaded bronze alloys.
8.91 g/cc — bushing and bearing stock weights.
Compare C932 against lead-free bearing bronzes.
Need bronze C932 parts machined?
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