An Analysis of the Lumber Planing Process: Part I

Report of study of the peripheral-milling process of planing lumber. The test apparatus consisted of a modified combination knife grinder and jointer. The lumber specimens, which ranged up to 20 feet long, were securely fastened to a strip of cold-rolled steel. With this arrangement feed speeds up to 600 FPM were obtained. All experimentation was at a nominal cutterhead RPM of 3600. In order to photograph the transient phenomena of the chip formation, photographs were taken at night with the shutter on the camera open to the flashing of a 1 microsecond photolight. The raw material was Douglas-fir heartwood. With low feed speeds and light cuts, the horsepower demand is approximately proportional to the number of jointed knives. A strong relationship exists between net cutterhead horsepower requirement and rake angle. When machining dry stock, a rake angle of 15? requires half as much power as does a 0-degree rake angle, and twice as much power as does a 30-degree rake angle. The tests indicate that the net cutterhead horsepower requirement is inversely related to clearance angle. The photos disclose, and the power readings confirm, that the most desirable gib type should present ample gullet space for the feeds and speeds contemplated. With relatively heavy cuts an approximately linear relationship exists between horsepower requirement and feed speed within the range of 100-300 FPM. A somewhat linear relationship between net cutterhead horsepower demand and depths of cut of 1/16 inch and greater can be observed. In comparing edge-grain specimens to flat-grain specimens in the portion of the tests reported, edge-grain stock requires 15 percent more power than flat-grain stock. At rake angles of from 10 to plus 40 degrees, green stock takes significantly more power than dry stock.

You must be logged in to download any documents. Please login (login accounts are free) or learn how to Become a Member