1.1: Milling Machines
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The milling machine is one of the most versatile machines in the shop. Usually they are used to mill flat surfaces, but they can also be used to machine irregular surfaces. Additionally, the milling machine can be used to drill, bore, cut gears, and produce slots into a workpiece.
The milling machine uses a multi-toothed cutter to remove metal from moving stock. There is also a quill feed lever on the mill head to feed the spindle up and down. The bed can also be manually fed in the X, Y, and Z axes. Best practices are to adjust the Z axis first, then Y, then X.
When an axis is properly positioned and is no longer to be fed, use the gib locks to lock it in place.
It is common for milling machines to have a power feed on one or more axes. Normally, a forward/reverse lever and speed control knob is provided to control the power feed. A power feed can produce a better surface finish than manual feeding because it is smoother. On long cuts, a power feed can reduce operator fatigue.
The following procedures are suggested for the safe operation of a milling machine.
- Have someone assist you when placing a heavy machine attachment like a rotary table, dividing head, or vise.
- Always refer to speed and feed tables.
- Always use cutting tools that are sharp and in good condition.
- Seat the workpiece against parallel bars or the bottom of the vice using a soft hammer or mallet. Check that the work is firmly held and mounted squarely.
- Remove the wrench after tightening the vice.
- Most operations require a FORWARD spindle direction. There may be a few exceptions.
- Make sure there is enough clearance for all moving parts before starting a cut.
- Make sure to apply only the amount of feed that is necessary to form a clean chip.
- Before a drill bit breaks through the backside of the material, ease up on the drilling pressure.
- Evenly apply and and maintain cutting fluids to prevent morphing.
- Withdraw drill bits frequently when drilling a deep hole. This helps to clear out the chips that may become trapped within the hole.
- Do not reach near, over, or around a rotating cutter.
- Do not attempt to clean the machine or part when the spindle is in motion.
- Stop the machine before attempting to make adjustments or measurements.
- Use caution when using compressed air to remove chips and shavings. They flying particle may injure you, or those around you.
- Use a shield or guard for protection against chips.
- Remove drill bits from the spindle before cleaning to prevent injury.
- Clean drill bits using a small brush or compressed air.
- Properly store arbors, milling cutters, collets, adapters, etc., after using them. They can be damaged if not properly stored.
- Make sure the machine is turned off and clean before leaving the workspace.