Entering angle kr is the angle between the main, leading cutting edge of the insert and the workpiece surface.
Lead angle ψr is the angle between the main, leading cutting edge of the insert and the center line of the tool.
Chip thickness, cutting forces and tool life are all especially affected by the entering angle/lead angle.
The most common entering/lead angles are 90°/0°, 45°, 10°/80° and those eliminated by round inserts, such as cutters using ball nose inserts at smaller depths of cut.
- Decreasing the entering angle, kr, or increasing the lead angle ψr, on straight edges reduces chip thickness, hex, for a given feed rate, fz. This chip thinning effect spreads the amount of material over a larger part of the cutting edge.
- Smaller entering angles/larger lead angles provide a more gradual entry into the cut, reducing radial pressure and protecting the cutting edge.
- Higher axial forces at decreasing entering/increasing lead angles will increase the pressure on the workpiece.
- Main application area is square shoulder milling.
- Generates mostly radial forces, in direction of the feed.
- The surface being machined will not be exposed to high axial pressure, which is advantageous for milling workpieces with a weak structure or thin walls, and in cases of unstable fixture.
Cutter assortment: CoroMill 290, CoroMill 390, CoroMill 490, CoroMill 590, CoroMill 690, CoroMill 790, CoroMill Plura and Auto-FS – and for special purposes, the side and face milling and grooving cutters: CoroMill 331, CoroMill 327/328 and the T-Max Q-cutter.
- General choice for face milling.
- Generates well balanced radial and axial cutting forces.
- Smooth entry into cut.
- Low tendency for vibrations when milling with long overhangs or smaller/weaker tool holders and couplings.
- Especially suitable for milling workpieces in short-chipping materials that easily fritter if excessive radial forces act on the gradually reduced amount of material left at the end of a cut.
- Formation of a thinner chip allows for high productivity in many applications because of the opportunity for higher table feed while maintaining a moderate cutting edge load.
Cutter assortment: CoroMill 245, CoroMill 345, T-Max 45 and Sandvik Auto program.
60°/30° to 75°/15° cutters
- Special purpose face mills offering larger depth of cut compared to the general choice face mills.
- Lower axial forces compared to 45° face mills.
- Better edge strength compared to 90°/0° cutters.
Cutter assortment: CoroMill 360, CoroMill 365, Auto AF.
- High-feed and plunge milling cutters.
The thin chip generated allows for very high feeds per tooth, fz, at small depths of cut and, consequently, for extreme table feeds, vf.
- The dominating axial cutting force is directed towards the spindle and stabilizes it. This is favorable for long and weak setups, as it limits vibration tendencies.
- For plunge milling of cavities, or whenever use of an extended cutter is required.
- Effective in hole making using three axis.
Cutter assortment: CoroMill 210, CoroMill 316 and CoroMill Plura high feed cutters.
Round inserts or cutters with a large corner radius
- Efficient roughing and general purpose cutters.
- Corner radius provides a very strong cutting edge.
- High table feed rate capability due to thinner chips generated along the long cutting edge.
- The chip thinning effect makes these cutters suitable for machining titanium and heat resistant alloys.
- Depending on cutting depth variations, ap, the entering/lead angle changes from 0° up to 90°, altering the cutting force direction along the edge radius, and consequently the resulting pressure during the operation.
Cutter assortment: CoroMill 200, CoroMill 300 and – at smaller depths of cut – CoroMill 390 radius insert cutters; the ball nose cutters CoroMill 216 and CoroMill 216F. Also, the solid carbide end mills, CoroMill Plura and CoroMill 316, are available in ball nose versions with a large corner radius.
(Content originally published by Sandvik Coromant on www.sandvik.coromant.com.)