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Bronze Speeds and Feeds
Guide · Updated October 28, 2026
"Bronze" covers very different alloys. Leaded bearing bronze (C932, SAE 660) machines almost like free-cutting brass. Phosphor bronze is tougher and stringier. Aluminum bronze (C954) is hard and abrasive, closer to a medium steel. Pick speeds for the alloy you actually have.
Size bushings accurately
Bearing bores and press fits live in tenths. Check your bore gage or mic against gage blocks first. The free Gage Block Calculator builds the stack.
Step by step
- Identify the alloy: C932 leaded bearing bronze, C510/C544 phosphor bronze, or C954/C955 aluminum bronze.
- Pick a starting SFM: Carbide: C932 about 500–800 SFM, phosphor bronze 300–500 SFM, aluminum bronze 200–400 SFM. HSS roughly a quarter to a third of those.
- Choose rake: Leaded bronze likes zero or slightly negative rake so the tool does not grab; aluminum bronze needs positive rake and a strong edge.
- Set chip load: Turning 0.004–0.010 in/rev; milling 0.001–0.004 in per tooth for 1/4–1/2 in cutters.
- Coolant: Leaded bronze often cuts dry or with mist; aluminum bronze needs flood coolant.
- Watch drills and reamers: Dub the drill lip (flatten rake) on leaded bronze so it does not self-feed.
- Finish and measure: Take a light finish pass and measure after the part cools.
Worked example
Turning a 2.000 in C932 bushing OD with carbide at 600 SFM: RPM = 3.82 × 600 ÷ 2.000 = 1,146 RPM. At 0.006 in/rev, feed rate = 1,146 × 0.006 = 6.9 in/min. If the same part were C954 aluminum bronze at 300 SFM: 3.82 × 300 ÷ 2.000 = 573 RPM, and at 0.006 in/rev the feed rate halves to 3.4 in/min.
Why drills grab in bronze
Leaded bronze and brass are so free-cutting that a normal drill helix pulls itself in. Grinding a small flat on the cutting lips (zero rake) stops the drill from grabbing and breaking through suddenly.
Common problems
A drill or boring bar pulling in means too much positive rake. Rapid tool wear on aluminum bronze means too much SFM. Torn finish on phosphor bronze means a dull tool or too little feed.
Tips
- Compare: brass speeds and feeds.
- Bores: use a dial bore gage.
- Reaming: reamer speeds and feeds.
FAQ
What SFM for bearing bronze?
About 500–800 SFM with carbide for C932 as a starting point.
Is aluminum bronze hard to machine?
Yes, it is tough and abrasive; run around 200–400 SFM with carbide.
Why does my drill grab in bronze?
Too much rake; dub the lips to zero rake.
Can I cut bronze dry?
Leaded bronze often can; aluminum bronze needs coolant.
Is bronze dust a hazard?
Leaded bronze contains lead; avoid dust and wash hands.
Related guides and calculators
- Brass Speeds and Feeds
- Copper Speeds and Feeds
- Turning Speeds and Feeds
- Drilling Speeds and Feeds
- Feeds & Speeds Basics
- All free machinist calculators
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