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 that extra care should always be taken when calculating this.
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, 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
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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 arbour boss, the deformation strength of the driving keys, and the capacity of the chip pockets.
Fly-wheel – 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 the intermittent machining. This is detrimental to the machining result and to productivity.
- Employing a fly-wheel 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 fly-wheels
- The need for a fly-wheel 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 fly-wheel as close to the tool as possible.
- Using a fly-wheel results in smoother machining, which in turn leads to a reduction in noise and vibration, and a longer tool life
- In addition to up-milling, a fly-wheel can be fitted to the arbour on which the milling cutter is set up
- In order to further improve stability when side and face milling, use the largest possible fly-wheel that the application permits
- Combining a number of round carbon steel discs, each with a centre hole and key groove to fit the arbour, remains the best method for constructing a fly-wheel
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 fly-wheels.
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.