maching oprations

Milling Machines: 101

Here’s some basics on milling machines courtesy of the Army Correspondence Course Program.
This is a long one, but if you scratch your head when someone says milling machine, this will give you the START to a basic understanding. Print it out and read it on the can. Make sure to click on read more to get to the whole article.

FIGURE 1. PLAIN MILLING MACHINE-KNEE TYPE.

1. Introduction
Milling machines were first invented and developed by Eli Whitney to mass produce interchangeable musket parts. Although crude, these machines assisted man in maintaining accuracy and uniformity while duplicating parts that could not be manufactured with the use of a file.
Development and improvements of the milling machine and components continued, which resulted in the manufacturing of heavier arbors and high speed steel and carbide cutters. These components allowed the operator to remove metal faster, and with more accuracy, than previous machines. Variations of milling machines were also developed to perform special milling operations. During this era, computerized machines have been developed to alleviate errors and provide better quality in the finished product.
2. Milling Machines
a. General. The milling machine removes metal with a revolving cutting tool called a milling cutter. With various attachments, milling machines can be used for boring, slotting, circular milling dividing, and drilling. This machine can also be used for cutting keyways, racks and gears and for fluting taps and reamers.
b. Types. Milling machines are basically classified as being horizontal or vertical to indicate the axis of the milling machine spindle. These machines are also classified as knee-type, ram-type, manufacturing or bed-type, and planer-type milling machines. Most machines have self-contained electric drive motors, coolant systems, variable spindle speeds, and power-operated table feeds.
(1) Knee-type Milling Machines. Knee-type milling machines are characterized by a vertical adjustable worktable resting on a saddle supported by a knee. The knee is a massive casting that rides vertically on the milling machine column and can be clamped rigidly to the column in a position where the milling head and the milling machine spindle are properly adjusted vertically for operation.
(a) Floor-mounted Plain Horizontal Milling Machine (figure 1 above).
[1] The floor-mounted plain horizontal milling machine’s column contains the drive motor and, gearing and a fixed-position horizontal milling machine spindle. An adjustable overhead arm, containing one or more arbor supports, projects forward from the top of the column. The arm and arbor supports are used to stabilize long arbors, upon which the milling cutters are fixed. The arbor supports can be moved along the overhead arm to support the arbor wherever support is desired. This support will depend on the location of the milling cutter or cutters on the arbor.
[2] The knee of the machine rides up or down the column on a rigid track. A heavy, vertical positioned screw beneath the knee is used for raising and lowering. The saddle rests upon the knee and supports the worktable. The saddle moves in and out on a dovetail to control the crossfeed of the worktable. The worktable traverses to the right or left upon the saddle, feeding the workpiece past the milling cutter. The table may be manually controlled or power fed.