Calculating feed per tooth
A critical factor in peripheral milling using side and face milling cutters is achieving a suitable feed per tooth, fz. Insufficient values cause serious disadvantages, so extra care should always be taken during calculation.
The feed per tooth, fz, should be decreased for deeper slots and increased for shallower ones, in order to maintain the recommended maximum chip thickness. For example, when full slotting with geometry M30, the starting value for maximum chip thickness should be 0.12 mm (0.005 inch).
Note: Because two inserts work together to cut the full slot width, feed is calculated using half the number of inserts zn.
| ae / Dcap (%)|| fz (mm/tooth)|| hex (mm)|
Depth of cut
For deeper slots, a special cutter can be ordered. If deeper slots are to be machined, feed per tooth should be decreased. If the slot is shallower, increase feed.
Note: The depth of a slot can be limited by the diameter of the arbor boss, the deformation strength of the driving keys and the capacity of the chip pockets.
Flywheel – on horizontal machines
Only a few teeth are engaged at any one time in side and face milling operations, which can generate heavy torsional vibrations due to intermittent machining. This is detrimental to the machining result and to productivity.
- Employing a flywheel is often a good solution for reducing these vibrations. Problems caused by insufficient power, torque and stability in the machine are often solved by the correct use of flywheels
- The need for a flywheel is greater in a small machine with low power, or in a machine with greater wear, than in a larger, more stable and powerful machine
- Position the flywheel as close to the tool as possible.
- Using a flywheel results in smoother machining, which in turn leads to a reduction in noise and vibration, and longer tool life
- In addition to up-milling, a flywheel can be fitted to the arbor on which the milling cutter is set up
- In order to further improve stability when side and face milling, use the largest possible flywheel that the application permits
- Combining a number of round carbon steel discs, each with a center hole and key groove to fit the arbor, remains the best method for constructing a flywheel
Gang milling using cutters mounted in a staggered pattern
Cutters that have bore mounting with 2 keyways can be arranged in a staggered pattern for milling more than one slot at the same time. Displacing the cutters in relation to each other assists in avoiding vibration. This also reduces the need for flywheels.
Milling of narrow and shallow slots and grooves
Versatile cutters have multiple edge inserts that are available in shapes to fit most types of small grooves. Common applications include the machining of internal circlip and seal ring grooves and of small straight or circular external grooves, particularly on components that cannot be rotated.
- A smooth entrance should be programmed when using circular milling.
- Consider the relationship between the cutter diameter and the hole diameter, Dc/Dw. The smaller the relationship, the larger the engagement will be.