January 5, 2022

What is the milling process?

What is milling

Milling is a process that involves the use of milling or cutting tools to remove material from the surface of a workpiece. The milling process uses cutting tools rotating at set speeds. Bring the cutting tools with the workpiece to start removing materials when they come with the workpiece.

Milling removes crevices from the surfaces of metals that cause corrosion. It gets rid of excess material off the surface of a workpiece. The process prepares metals for the application of corrosion-resistant coating. Milling machines feature horizontal milling machines with a horizontal spindle. Like the name, the cutting tool is on this horizontal spindle. Feed the cable in a vertical, cross, or horizontal direction.

Universal milling machines are milling machines that perform all kinds of milling operations. They feature a table fitted with all motions and a dividing head with change gears. The table can pivot at any angle up to 45 degrees in both directions. Simplex milling machines feature a spindle that only travels in one milling direction. Most of these machines only travel in a vertical direction.

Duplex milling machines are two milling machines positioned opposite each other. These either work independently as or as one machine with two simultaneous spindles. They travel both horizontally and vertically. Triplex milling machines have a spindle that can travel in all three axes, such as XY and Z.

CNC milling process

A CNC milling machine uses a rotating cutter in a cylindrical shape. The plasma cutter moves in multiple Axes. The plasma cutter creates slots and holes in the material that later turns into a part. Standard machines operate on three to five axes. That makes precise cuts and more detail than on 2 Axis.

Modern CNC milling machines are either horizontal or vertical machine centers. They accommodate plastics, ceramics, and composite materials. Several technical features are part of the milling machine, such as automatic tool changers and magazines.
Coolant systems have longer hours of operating the machine without feeling the heat. The plasma machines run smoothly without manual help. That reduces fatigue since the user is more of an operator than running the plasma machine. The vertical milling machine has a vertically oriented spindle axis.

It has long and thin cutting tools, whereas the horizontal machine has shorter and thicker cutting tools. Vertical plasma machines are more versatile than horizontal machines. CNC milling machines come in different sizes that fit multiple sizes and businesses. It is reliable, and I urge you to consider your needs before one.

Types of the milling process

Slot Milling

The process features the width of the cutter, less than the width of the workpiece. It makes a slot in the workpiece using thin cutters. To cut the piece in two, make a thin slot go through the depth of the workpiece.

Side Milling

The process is when you produce a flat vertical surface in the workpiece. The depth of the cut is manipulated by rotating the vertical feed screw of the table.

Straddle Milling

It is when you need two or more parallel vertical surfaces machined in a single cut. Complete the process by mounting two side milling cutters on the same arbor, as you set them apart such that they straddle the workpiece.

CNC Milling Operations

Up (and Down) Milling

It is also known as conventional milling. Up milling is when the cutter rotates against the direction of the table feed. In contrast, down milling involves a milling cutter that rotates along the direction of the table feed. The difference lies in the load. In up milling, the chip load on teeth increases gradually, while in down milling, the chip load decreases.

Form Milling

The form milling process allows the machining of special contours made of curves and straight lines in a single cut. This is made possible with formed cutters, shaped to the contour of the cut, or with a fly cutter ground. It has to be specifically for the job. Standard form milling involves milling half-round recesses on the workpiece.

Turret Milling

Turret milling is done by drilling, cutting, and shearing. The spindle is stationary during the milling process, while the table moves along the X and Y axes. This process is for lighter operations.

Types of Milling Machines

  • Horizontal or Plain Milling Machine.
  • Vertical Milling Machine.
  • Universal Milling Machine.
  • Simplex Milling Machine.
  • Duplex Milling Machine.
  • Triplex Milling Machine.
  • Rotary Table Milling Machine.
  • Tracer Controlled Milling Machine.

What Is a Milling Cutter

Milling cutters are cutting tools used in milling machines or machining centers to perform milling operations. They remove material by their movement within the milling machine.

CNC milling machine function

It removes materials from a workpiece.

Milling machine parts

Column and Base

The column comes with a base, and it is the casting that supports all other parts of the milling machine. The column features an oil reservoir and a pump that lubricates the spindle. It rests on the base, and the knee base has a coolant reservoir and a pump. These are required to cool off the milling machine during teaching operations.


The knee is a casting that supports the saddle and table. All gearing mechanisms are within the knee. It is secured to the column by dovetail ways, supported, and adjusted by a vertical positioning screw. That is the elevating screw. It adjusts the knee up and down, raising or lowering the lever. Use the help of a hand or power feed.


It is a rectangular casting that comes on the top of the saddle. It holds the work or work holding devices. The table comes with multiple T-slots holding the work and work holding devices. You are allowed to control the table by hand or by power. To move the table by hand, engage and turn the longitudinal hand crank. To move it through power, engage the longitudinal direction feed control lever.


It is the shaft used to hold and drive the cutting tools of the milling machine and mount the spindle on the bearings and supported by the column. Move the gear trains by the electric motor. The gear trains are inside the column.

Milling machine uses

  • Drill
  • Bore
  • Cut gears
  • Produce slots

Face milling

Face milling is the milling of flat surfaces at right angles to the axis of rotation of the cutter (Source). It removes the material by rotating the facing tool in a counterclockwise direction. At the same time, the table feeds the workpiece across the cutter.

Gang Milling

Gang milling is a process whereby more than two milling cutters are involved in a setup like horizontal milling. All the cutters perform a uniform operation, and the milling cutter may also perform distinct operations. This operation is ideal for producing duplicate parts.

Vertical Milling Machines

Vertical milling machines have the spindle perpendicular to the table. The spindle head is fixed to a vertical column that rotates at an angle, and the cutting head is on the spindle. Vertical milling machines allow the adjustment of the spindle either upwards or downwards. These machines are for precision work.

Horizontal Milling Machines

A horizontal milling machine is a milling tool with a spindle parallel to the worktable. It is for processing various planes, inclined planes, and grooves with cylindrical milling cutters, disc cutters, angle cutters, forming cutters, end mills, and more tools.

David D. Hughes
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