Milling machines

1870

Most metal-working machinery performs its work by presenting the cutting bit to the workpiece, which is either clamped in place, or (in the case of a lathe) spun between centers. The drill press is a simple example.

None of these match the versatility of the milling machine, which basically reverses the functions.  The workpiece, rather than the cutter, is moved. The cutter is fixed to a spindle which rotates, but doesn't change position.

The workpiece is held in a vice, or other special fixture, which is bolted securely to the table. The entire table, with fixtures attached, is moved as a single unit by hand-cranks, or sometimes using a geared driveshaft.

The table is moved from left to right, allowing the cutter to remove material gradually as it comes into contact with the workpiece. The table can also be moved vertically, creating room to bolt on special fixtures for angular cutting.
Milling machine introduced, 1870

  One-Man-Show
The milling machine can do it all. It can true up a surface, or mill lengthwise features like slots and grooves. If an adapter is used to orient the spindle vertically (instead of horizontally, as shown) it can mill an edge or make plunging cuts. Fixtures can allow cutting at compound angles, as may be required to cut or grind teeth on gears.

Spindle cutters, multi-axis tables, 1870

  Expanded Function
Derived by expanding on functions used in other machines, the milling machine introduces a multi-axis movable table, plus the ability to mount cutters with many different profiles. The one shown here is for milling a flat surface. Later milling machines will have vertically-oriented main spindles, and three-axis tables. This will allow general milling operations on surfaces that are horizontal or vertical, using an all-purpose end-mill. It will also enable vertical boring operations, with precise positioning.


Profiled milling cutters, 1870

  Shaped Profiles
Cutters with central holes are mounted on the spindle of horizontal milling machines, and are available with many cutting profiles. Cutters for machines with vertical spindles are gripped by their tapered shanks.


Versatile holding fixtures, 1870

  Vertical Adjustment
Another key feature of the milling machine is the vertical table movement, which allows extra space between the cutter and the table, to accommodate all kinds of special holding fixtures. Some are used to orient the workpiece at compound angles.


Complicated milling, 1870

  Flexible Operation
These diagrams illustrate the variety of operations that can be performed on a milling machine. Most could not be performed on any other type of general-purpose machine.


Extended functions, 1870

  Spillover of Ideas
The machinery shown above illustrates the ongoing evolution of equipment designs, as other kinds of machines are adapted to benefit from the expanded capability of milling-style cutting spindles, and bolt-on fixturing.