Machining
Swiss Machining vs CNC Turning
Swiss machining feeds bar stock through a guide bushing so cutting happens at the point of support, which holds long slender parts that would whip on a conventional lathe. CNC turning chucks the part and brings tools to it. Diameter, length to diameter ratio, and lot size decide the quote.
| Swiss Machining | CNC Turning | |
|---|---|---|
| Diameter range | 1 to 32 mm typical, 38 mm max | 5 to 500+ mm |
| Length to diameter | 20:1 with guide bushing support | 3:1 unsupported, more with tailstock |
| Tolerance | ±0.0025 to 0.005 mm achievable | ±0.0125 to 0.025 mm typical |
| Bar stock | Ground bar, adds 10 to 15 percent | Standard cold drawn bar |
| Setup time | 2 to 6 hr | 0.5 to 1.5 hr |
| Done in one | Milling, cross drilling, backwork standard | Live tooling optional, often a second op |
| Economic lot size | 500 to 1,000+ parts | 1 to 10,000, flexible |
Choose Swiss Machining when
- Diameters under 32 mm with length over 3x diameter
- Medical pins, fittings, connector parts at volume
- Complete part off the machine, no second op
Choose CNC Turning when
- Parts over 38 mm diameter
- Lots under 500 pieces
- Short chunky geometry with large bores
The verdict
Under 32 mm diameter, past 3:1 length to diameter, and above roughly 1,000 pieces, Swiss wins on both tolerance and cost per part. Large diameters, short parts, and small lots belong on a CNC lathe. Do not pay 4 hours of Swiss setup for 100 pieces of easy geometry.
Cost comparison
Swiss shop rates run $75 to $110/hr against $60 to $90/hr for CNC turning, and a 2 to 6 hour Swiss setup costs $200 to $600 before the first good part. But a 3 mm medical pin comes off a Swiss complete in 25 s versus two operations totaling 3 minutes on a lathe plus mill. Crossover lands around 300 to 1,000 pieces depending on setup complexity. Add 10 to 15 percent to material for ground bar when the guide bushing requires it.
Common questions
Why does Swiss machining need ground bar stock?
The guide bushing grips the bar with only 0.005 to 0.01 mm of clearance. Standard cold drawn bar varies too much in diameter and straightness, causing chatter, bushing wear, and taper on the part. Ground and polished bar adds 10 to 15 percent to material cost. Guide bushless Swiss machines relax this requirement but give up some of the length to diameter advantage.