It is even possible to do work that might now be done by wire EDM in some cases. Starting from a drilled or cored hole, a planer with a boring-bar type tool can cut internal features that don't lend themselves to milling or boring.
Helical planing
Although the archetypal toolpath of a planer is linear, helical cutting can be accomplished by coupling the table's linear motion to simultaneous rotation. The helical planing idea is similar to both helical milling and single-point screw cutting.
Current Usage
Planers and shapers are now, because other machine tools have mostly eclipsed them as the tools of choice for doing such work. However, they have not yet disappeared from the metalworking world. Planers are used by smaller tool and die shops within larger production facilities to maintain and repair large stamping dies and plastic injection molds. Additional uses include any other task where an abnormally large block of metal must be squared when a horizontal grinder or floor mill is unavailable, too expensive, or otherwise impractical in a given situation. As usual in the selection of machine tools, an old machine that is in hand, still works, and is long since paid-for has substantial cost advantage over a newer machine that would need to be purchased. This principle easily explains why "old-fashioned" techniques often have a long period of gradual obsolescence in industrial contexts, rather than a sharp drop-off of prevalence such as is seen in mass-consumer technology fashions.
Configurations and sizes
There are two types of planers for metal: double-housing and open-side. The double-housing variety has vertical supports on both sides of its long bed; the open-side variety has a vertical support on only one side, allowing the workpiece to extend beyond the bed. Metal planers can vary in size from a table size of 30"×72" to 20'×62', and in weight from around 20,000 lbs to over 1,000,000 lbs.
History
Early planing ideas are known to have been underway in France in the 1750s. In the late 1810s, a variety of pioneers in various British shops developed the planer into what we today would call a machine tool. The exact details have been contentious and will probably never be known, because the development work being done in various shops was undocumented for various reasons. Roe provides a short chapter that tells the story as thoroughly as he was able to discover it.
