High feed milling
What is successful high feed milling?
When machining aluminium, and sometimes when machining cast iron with CBN or ceramic inserts, cutting speeds of more than 1000 m/min can be used, which result in a very high table feed, vf. This type of machining is called High Speed Machining (HSM).
In milling short-chipping materials, such as grey cast iron, a face milling cutter with an extra close pitch can be used, resulting in high table feed. In HRSA materials where cutting speed is normally low, an extra close pitch results in a high table feed.
Face milling with a very high feed per tooth (up to 4 mm/tooth) is possible when using cutters that have small entering angles or when using round insert cutters, due to their chip thinning effect. Although the depth of cut is limited to less than 2.8 mm, the extreme feed makes it a highly productive milling method. Specific cutter concepts are optimized for extreme high feed milling at small axial depths of cut. A small entering angle is the precondition required for applying a light and fast, high feed.
Choice of tools
High feed cutters||
Round insert cutters||
|Max. cutting depth (ap),
|1.2 - 2||1.3||1.3||10||7/8||2.8|
|Cutter dia. (DC),
|25 - 160||10 - 25||4 - 20||25 - 160||10 - 42 /|
25 - 125
|63 - 160|
High feed cutters:
- Productive high feed face mills with a 10° entering angle, allowing for very high feed per tooth,
- High feed rates at small depths of cut,
- High precision tools optimized for high speed machining of hardened steel
- Roughing to semi-finishing of contours and asymmetrical configurations at extreme feed rates
Note: For round insert and radius cutters, the
ap value should be kept far below the maximum recommended value to allow high feed milling
Round insert cutters:
- Increased chip thinning effect at reduced axial cut
- Smooth cutting action
- General purpose cutters for tough or light conditions
How to apply
Cutters with a small entering angle
Cutters with very small entering angles enable a dramatic increase in the feed,
fz, due to the chip thinning effect when
ap is small.
iC||Dimensions, mm||Uncut material|
Maximum chip thickness is dramatically reduced by a low entering angle. This allows extremely high feed rates to be used without over-loading the inserts.
Note: Avoid machining all the way against a 90° shoulder, because the positive effect of a low approach angle will be lost, i.e. the depth of cut will dramatically increase.
As always, the feed rate has to be reduced and adapted depending upon specific conditions and to avoid vibrations, which can damage the inserts.
Round insert cutters
Chip thickness, hex, varies with round inserts and depends on the depth of cut,
ap. When using high feed milling techniques with a round insert cutter, the depth of cut should be kept low (max. 10% of insert diameter, iC, otherwise the chip thinning effect is reduced and the feed has to be decreased, see illustration).
Note: When using round insert cutters, it is important to reduce the feed when approaching a wall/shoulder, because the depth of cut suddenly increases.
Strong inserts for general roughing
On round inserts, the chip load and entering angle vary with the depth of cut. The best performance is achieved when the depth of cut is smaller than 25% x insert diameter, iC.