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Should I use a screw machine or CNC machining?
Use screw machines for small round parts at high volume: Swiss and multi-spindle machines turn pins, bushings and fittings up to about 2.5 in (64 mm) diameter in 5–90 second cycles, holding ±0.001 in (±0.025 mm). Use CNC turning and milling below about 1,000 parts, for larger diameters, prismatic or milling-heavy parts, and designs that change often.
Which is cheaper at your quantity?
The same turned shaft, each process in a suitable material (12L14 and 12L14).
| Quantity | Screw machining | CNC machining |
|---|---|---|
| 10 | $100 | $67.10 |
| 50 | $22.10 | $24.70 |
| 100 | $12.40 | $18.90 |
| 500 | $4.59 | $12.40 |
| 1,000 | $3.62 | $11.00 |
| 5,000 | $1.78 | $10.00 |
| 10,000 | $1.48 | $9.97 |
| 50,000 | $1.23 | $9.93 |
| 100,000 | $1.20 | $9.93 |
Where each pays off
Screw machine products
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- Tooling
- 1–4 weeks for form tools and cams
- First article
- 1–3 weeks
- Production
- 3–6 weeks per release
±0.001 in (±0.025 mm) standard; ±0.0002–0.0005 in (±0.005–0.013 mm) on critical diameters
Production machining, turning, and sawing
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- First article
- 1–3 weeks
- Production
- 2–6 weeks per release
±0.005 in (±0.13 mm), or ISO 2768-m
Which should you pick?
Pick Screw machining when
- You need 10,000 or more turned parts a year
- Diameters are under about 1.25 in (32 mm) on Swiss or 2.5 in (64 mm) on multi-spindle
- Parts are long and slender, over 10:1
- The alloy is free-machining, such as 12L14, 1215, C360 or 303
Pick CNC machining when
- You need fewer than about 1,000 parts
- Diameters exceed about 2.5 in (64 mm)
- The part is milling-heavy or prismatic
- The design changes often
Key differences
| Screw machining | CNC machining | |
|---|---|---|
| Setup | Cam multi-spindle setups can take a full shift | Programming and setup fixed per job, typically hours |
| Cycle time | 5–90 seconds per part | Longer; machine time is the main cost |
| Diameter range | 0.020–1.25 in (0.5–32 mm) Swiss; to about 2.5 in (64 mm) multi-spindle | To about 16 in (400 mm) on production lathes |
| Dedicated tooling | Form tools and cams $500–$5,000 per job; little for CNC Swiss | None |
| Practical minimum | About 1,000 on CNC Swiss; 10,000+ on cam multi-spindle | One part |
| Slender parts | Guide bushing supports the cut past 10:1 length to diameter | Needs tailstock support; slender parts chatter |
Questions
What is the difference between Swiss and multi-spindle screw machines?
Swiss machines support the bar in a guide bushing next to the cut, so they excel at long, slender, tight-tolerance parts up to about 1.25 in (32 mm). Multi-spindle machines cut 4–8 parts at once and win on cost for high-volume, shorter parts up to about 2.5 in (64 mm).
What is the minimum order for screw machine parts?
CNC Swiss work is often practical from about 1,000 pieces. Cam multi-spindle jobs usually need 10,000 or more to justify setup. Many shops quote a minimum lot charge instead of a strict piece count.
Is screw machining the same as CNC turning?
Both turn parts from bar. Screw machines are bar-fed automatics built for small diameters and long runs, where cycle time dominates cost. CNC turning centers set up faster and handle larger diameters, where setup time dominates.
Try both on your part.
The builder prices the same geometry in every suitable process and material, with DFM for each.