is caused by insufficient cutting thrust or by cutting into the
grain in an unfavorable direction. It is a defect below the planed
by too small a hook angle in a soft wood. It is a defect above the
CUTTING THRUST: causes
torn grain or rough finish quality
Experience has shown that a hook angle of 22° is excellent for soft wood machining. A hook of 10° is excellent for hard wood machining. Since many mills use both hardwoods and softwoods a hook angle of 15° is recommended. If a slightly different hook angle is desired this may be accomplished by either extending the knife further out of the head or by back grinding the knife. Back grinding is done by face grinding the knife. After this is done you must then reprofile the knife so that the pattern will not be distorted.
tend to reduce torn grain.
tend to reduce fuzzy grain
Primarily determines the rigidity and lifetime of the tooling. The
bigger the angle, the longer the knife's lifetime between sharpenings.
A large blade angle combined with high quality tooling steel helps
in avoiding chipped edges. When the edge of a knife chips, usually
caused by cutting into a foreign substance, it leaves a raised streak
in the stock after planning.
The smaller the blade angle, the more material has to be ground
off for a particular profile. More grinding time is involved which
is unfavorable for short runs.
Knives used in joint heads are ground with a small blade angle
so that more joints can be done with less land left, thus increasing
A dull knife makes itself pull hard, increases vibration and
pounding and tends to produce fuzzy grain.
Makes sure that only the lead edge of the knife is in contact
with the lumber. This allows the metal behind the lead edge to run
clear of the lumber. The air flow behind this lead edge on a knife
keeps the blade cool while it is in operation thus preventing burn
marks. The bigger the clearance the better the cooling effect and
the less pitch buildup.
CLEARANCE ANGLE: Used
for profile knives on side cuts to reduce drag. Side clearance should
be used on most profiles but must be used on knives with 55°
or more angle. Otherwise, the knife gets dull very fast on the side
flanks and burn marks will appear at these points.
combination of hook angle and blade angle basically determine the
surface quality of the lumber.
HERE FOR BASIC GUIDLINES FOR SOFT WOODS AND HARD WOODS
HERE FOR CUTTING ANGLES AND HOOK ANGLES
Click here for Cutting
Marks Per Inch Chart
and Rates of Feed
reach a friendly voice, call during our hours of operation:
Monday through Friday, 9 a.m. to 6 p.m. EST
(Eastern Standard Time)
Wood Tech Enterprises
Our website: www.woodtechtooling.com
P.O. Box 2226
Fairview, NC 28730 USA
15 Khristy Scott Lane
Fairview, NC 28730 USA
Copyright © 1998-2011 Wood Tech Enterprises, Inc. All Rights
Reserved. Designated trademarks and brands are the property of their
respective owners. Wood Tech is not responsible for typographical
errors. Prices are subject to change. All prices are in U.S. Dollars.