Machine Tools

Planers remove metal in a series of straight cuts by reciprocating (moving back and forth) the workpiece as the single-point tool feeds. The fixed tool is rigidly supported while the workpiece moves on precision ways for the full length of the cut, thus ensuring maximum accuracy. The rigidity of the tool allows the use of powerful motors, up to 150 hp, which permits higher production speeds and the use of multiple tooling with extremely heavy cuts and feeds. Planers are typically big machines used for handling the largest and heaviest work that can be supported on the machine table, as much as 75 tons A lathe turns an object on a horizontal axis so it can be cut with a fixed tool. Photograph by Pedro Coll. Stock Market. Reproduced by permission.
(68 tonnes). Planers may be fitted with hydraulic tracing attachments to enable them to cut curved surfaces.

There are two distinct types of planers, the single-housing, or open-side planer, and the double-housing planer. Double-housing planers are the most widely used and provide the greatest tool support rigidity. The major components of a double-housing planer are the bed, table, housings, arch, cross rail, and heads (side and rail). The bed is the foundation to which the housings are attached. The bed is provided with precision ways over its entire length and supports the reciprocating table.

The table supports the workpiece and reciprocates along the ways of the bed. The table is slightly less than half the length of the bed and its travel determines the dimensional capacity of the machine in length of stroke. The housings are rigid box-type columns placed on each side of the bed and table. They are heavily braced and ribbed to absorb the large cutting forces encountered in planing. The arch joins the housings at the top for greater rigidity of construction and also houses the drive mechanism for tool feeding. The cross rail is a rigid horizontal beam mounted above and across the table on the vertical ways of the columns. It supports the rail heads and provides for horizontal feeding of the cutting tools.

The heads carry the cutting tools and are equipped with "clapper" blocks that lift the tools clear of the work on the return stroke of the table. Single-housing or open-side planers support the cross rail from a single column. This permits wide workpieces to overhang the table on the open side if necessary.

Planers require many strokes of the workpiece to complete a cutting operation. Horizontal and vertical mills are much more efficient at metal removal than planers and have replaced planers for production work.