Application tips for external turning
Cut in one pass (for example, a tube)
It is recommended to machine the whole cut in one pass to direct the force into the chuck/spindle in an axial direction.
Outer diameter (OD) of 25 mm (0.984 inch)
Inner diameter (ID) of 15 mm (0.590 inch)
Depth of cut, ap = 4.3 mm (0.169 inch)
Resulting thickness of the wall = 0.7 mm (0.028 inch)
| OD = 25 mm (0.984 inch)|| ap 4.3 mm|
ID = 15 mm
An entering angle close to 90° (lead angle 0°) can be used for directing the cutting forces in the axial direction. This leads to minimal bending forces on the component.
Cut in two passes
Synchronized upper and lower turret machining will level out radial cutting forces and avoid vibration and bending of the component.
Slender/thin wall components
When turning slender/thin wall components, consider the following:
- Use an entering angle close to 90° (lead angle 0°). Even a small change (from a 91/-1 to a 95/-5 degree angle) will impact the cutting force direction during machining
- The depth of cut,ap, should be greater than the nose radius, RE. A large ap increases the axial force, Fz, and decreases the radial cutting force, Fx, which causes vibration
- Use an insert with sharp edge and small nose radius, RE, that will generate low cutting forces
- Consider using Cermet or PVD grade, to provide wear resistance,and a sharp insert edge,which is preferable in this type of operation
Follow steps 1–5 to avoid damage of the insert edge. This method is very favorable for CVD coated inserts, and may reduce fractures considerably.
Keep the distance of each step (1–4) the same as the feed rate to avoid chip jamming.
Machine the final cut in one vertical cut, starting from the outer diameter toward the inner diameter.
Problems with wrap-around chips on the radii can also occur if machining from inner to outer diameter when facing up on the shoulder. Changing the tool path can reverse the chip direction and solve the problem.
Start with the facing (1) and the chamfer (2). If possible, and if geometrical conditions on the workpiece allow it, machine the chamfer (3). The longitudinal cut (4) is the last operation and the insert will have a smooth entrance and exit during the machining.
Facing shall be the first operation to set the reference point for the component for the next pass.
Burr formation is often a problem at the end of the cut (when leaving the workpiece). Leaving a chamfer or a radius (rolling over a corner) could minimize or avoid burr formation.
A chamfer on the component will lead to a smoother entry of the insert edge (both in facing and longitudinal turning).
When machining interrupted cuts:
- Use a PVD grade to provide edge line toughness in applications with fast interruptions, for example, hexagonal bars
- Use a tough CVD grade to provide bulk toughness in applications with big components and heavy interruptions
- Consider using a strong chip breaker to add sufficient chipping resistance
- It can be beneficial to turn off coolant to avoid thermal cracks
Finishing component with undercut (grinding relief)
Use the biggest possible nose radius, RE, for longitudinal and face turning, leading to:
- A strong edge and more reliability
- Good surface quality
- The possibility to use high feed
Do not exceed the width of the undercut. Perform the undercut as the last operation, to remove burrs.