CNC Turning Lathe Types and Materials

• Horizontal CNC Lathe (2-Axis): The common configuration with a horizontal bed and spindle axis parallel to the floor. Two axes are X (cross travel) and Z (longitudinal travel). Spindle bore diameters range from 45 mm to 300 mm. Maximum turning length varies from 300 mm to 3,000 mm. These lathes handle bar work, chucked parts, and shaft components. Typical spindle power is 5.5 kW to 37 kW.

• Vertical CNC Lathe (VTL): The spindle is oriented vertically with a horizontal chuck face. Gravity assists in holding large-diameter, heavy workpieces (500 mm to 4,000 mm diameter). These machines are specified for brake drums, flywheels, and large bearing rings. Chip removal is improved compared to horizontal lathes because chips fall directly into the conveyor.
• Swiss-Type Lathe (Sliding Headstock): The workpiece moves axially through a guide bushing while tools remain stationary. Maximum bar diameter is typically 20 mm to 38 mm. Multiple tool posts (up to 12 stations) work simultaneously on the same part. Swiss lathes produce long, slender parts such as bone screws, dental implants, and electronic connectors. Cycle times are 30 to 50 percent shorter than conventional lathes for parts longer than 10 times the diameter.
• Multi-Axis Turning Center (3 to 7 Axes): Additional axes include Y (off-center milling), C (spindle positioning), and live tooling. Y-axis travel is usually 60 mm to 120 mm. These machines perform milling, drilling, tapping, and turning in one setup. A 7-axis turning center may include two spindles and two turrets. Typical application is complex parts requiring hexagonal flats, cross holes, or slots.
• Dual-Spindle Lathe (Main and Sub-Spindle): The main spindle machines the first operation. Then the part transfers to a synchronized sub-spindle for back-working. Transfer time is 1 to 5 seconds. This configuration eliminates secondary operations and reduces handling time by 40 to 60 percent. Dual-spindle lathes are common in automotive transmission component production.
• Lathe with Automatic Bar Feeder: The lathe is integrated with a bar loading system that feeds 3-meter to 4-meter bars. Bar diameters from 5 mm to 80 mm are common. Production runs of 1,000 to 10,000 parts can run unattended overnight. The bar feeder operates on hydraulic or pneumatic principles, pushing the bar after each part cutoff.
• Gantry-Loaded Turning Cell: A gantry robot loads raw stock and unloads finished parts into bins. This configuration is used for high-volume production (50,000+ parts per month) of simple geometries such as bearing races or pulley blanks. The gantry may serve two to four lathes simultaneously.
• CNC Gang Tool Lathe: Tools are mounted on a fixed block (gang plate) rather than a turret. X-axis travel is short (100 mm to 200 mm). Gang tool lathes offer faster indexing than turrets (0.1 to 0.3 seconds per tool change). They are used for small parts under 50 mm diameter where cycle time is below 30 seconds.

Materials Used in CNC Turning Lathes

Bed and Frame Materials

The machine base absorbs cutting forces and vibration. Most production lathes use cast iron grades such as FC300 (JIS) or EN-GJL-300 (ISO). Composition includes 3.2 to 3.5 percent carbon, 1.8 to 2.2 percent silicon, and 0.6 to 0.9 percent manganese. Tensile strength is 300 MPa minimum. Cast iron provides vibration damping capacity 5 to 8 times greater than steel. The weight of a cast iron bed for a 2-meter lathe ranges from 1,500 kg to 2,500 kg. High-end lathes use polymer concrete (epoxy granite) beds. Polymer concrete contains 90 to 94 percent mineral aggregates (granite, quartz, basalt) and 6 to 10 percent epoxy resin. Damping capacity is 8 to 10 times that of cast iron. However, polymer concrete costs 40 to 60 percent more than cast iron and requires precise curing at 40°C for 48 hours.

Spindle and Bearing Materials

The spindle is forged from 20CrMo or 40Cr alloy steel (similar to AISI 4130 or 5140). Forged spindles have tensile strength of 800 to 1,000 MPa. Spindle noses conform to A2-5, A2-6, or A2-8 standards. The taper section (typically Morse or HSK) is case-hardened to 58 to 62 HRC to a depth of 0.8 to 1.2 mm. Bearings are angular contact ball bearings or tapered roller bearings. Bearing material is 100Cr6 (AISI 52100) bearing steel with 58 to 62 HRC. For speeds above 6,000 rpm, ceramic hybrid bearings are used: silicon nitride (Si3N4) balls with steel races. Silicon nitride density is 3.2 g/cm³ compared to 7.8 g/cm³ for steel, reducing centrifugal force on the balls by 60 percent.

Turret and Tool Holding Materials

The turret body is cast from ductile iron FCD600 (JIS) or EN-GJS-600-3 (ISO). Ductile iron provides tensile strength of 600 MPa with elongation of 3 percent. Tool holders are made from 42CrMo4 (AISI 4140) hardened to 45 to 50 HRC. The VDI (Verein Deutscher Ingenieure) tool interface has hardness of 55 to 60 HRC at the clamping surfaces. Live tooling (driven tools) uses hardened gears of 20MnCr5 (similar to 5120) case-hardened to 58 to 62 HRC. Gear modules range from 1.0 to 2.5 mm, depending on torque requirements.

Guideways and Ballscrews

Linear guideways are made from 100Cr6 bearing steel with precision grades P5 or P4 (ISO). Rail hardness is 58 to 64 HRC. Recirculating balls are 440C stainless steel for corrosion resistance or ceramic (Si3N4) for high-speed applications (above 60 m/min). Ballscrews use the same steel, with lead accuracy of ±0.008 mm per 300 mm for C5 grade or ±0.003 mm for C3 grade. Ball nuts are made from bronze (CuSn8) or steel with PTFE-lined returns to reduce friction. The travel speed of ballscrews on CNC lathes ranges from 10 m/min (heavy cutting) to 40 m/min (finishing operations).