Planning for Knife Wear from Dense, Acidic Woods

Planning for Knife Wear from Dense, Acidic Woods

The species and environment of wood have a dramatic effect on the sharpness of knives and other cutting equipment. Certain woods are denser or naturally more acidic than others and thus dull blades faster. Soil composition also affects the acidity of the trees that grow in them. White oaks, for example, tend to have higher acidity in the Midwest (particularly Indiana) than other areas. The environment likewise affects density: long, cold winters produce trees with smaller, denser rings.

galvanized M-Series conveyor for waste material from Biomass Engineering & Equipment
Pictured is a galvanized M-Series SMART Conveyor™ from Biomass Engineering & Equipment, a division of Veneer Services®.

Understanding the characteristics of the wood your mill processes provides two advantages. One, it enables you to make better choices regarding equipment. You may want to consider a galvanized finish on your waste handling conveyors if your mill processes highly acidic woods, for example. Not adding a galvanized coating or otherwise installing a protective liner for such conditions may result in more maintenance and ongoing cost than your mill would spend on galvanization. A galvanized conveyor is thus be a better value under these circumstances than a lower-priced conveyor with a paint or powder coat finish.

Micro Micro Beveler - Blade Sharpener Tool for woodworking Rotating Blades
Micro Beveler from Raute.

The second advantage of understanding the characteristics of your wood is that it allows you to better plan for maintenance. Woods with higher acidity and density will dull blades faster, so you will have to sharpen them more often to achieve optimal performance. Because of this, you may want to consider knife guards to protect your knives and workers during blade changes. To reduce downtime, you may also want to consider a tool such as Raute’s micro beveller, which will hone knife edges while they’re attached to the machine.

Butt flare reducer for log processing at sawmills and veneer mills.
Butt flare reducer from Veneer Services®.

Because maintenance will occur more often with denser and more acidic woods, you should furthermore seek out machinery that allows personnel to perform maintenance faster to minimize downtime. Certain cutterheads like those on our butt flare reducer have multifaced blades, which allow maintenance personnel to flip them once before sharpening. Our butt flare reducer further helps with maintenance by slowing the speed it rotates the logs when it senses a heavy load as will occur when the cutters dull. Slowing the turn speed allows the machine to continue to process logs without overloading the cutter system and thus reduces the urgency of maintenance.

Below is a chart of the average pH values and dried densities of common North American wood species. Use the chart for planning at your mill, and contact us with any needs regarding maintenance, processing, and waste handling. We have many years of experience and are happy to assist.

Softwoods Average pH Average Dried Density   Hardwoods Average pH Average Dried Density
Alpine Fir 6 33 lbs/ft3 American Beech 5.5-6.2 45 lbs/ft3
Balsam Fir 5.4 25 lbs/ft3 American Black Ash 5.5 34 lbs/ft3
Black Spruce 5.7 28 lbs/ft3 American White Ash 5.4-6.0 42 lbs/ft3
Canadian Red Spruce 5.5 27 lbs/ft3 American White Elm 6.0-7.6 35 lbs/ft3
Douglas Fir 3.3 32 lbs/ft3 Balsam Poplar 6.4 23 lbs/ft3
Eastern Canadian Spruce

(White Spruce)

5.5 27 lbs/ft3 Black Locust 5.3 48 lbs/ft3
Eastern Hemlock 5.5-6.2 28 lbs/ft3 American Cherry

(Black Cherry)

4.0 35lbs/ft3
Jack Pine 5.4 American Mahogany 5.1-6.7 37 lbs/ft3
Pacific Silver Fir
(Amabilis Fir)
27 lbs/ft3 Chestnut 3.6 30 lbs/ft3
Red Pine 5.2-6.0 34 lbs/ft3 Largetooth Aspen 5.8 27 lbs/ft3
Sitka Spruce 4.0-5.5 27 lbs/ft3 Oak 3.3-3.9 *45-47 lbs/ft3
Western Hemlock 4.8-5.4 29 lbs/ft3 Quaking Aspen 5.4 26 lbs/ft3
Western Red Cedar 2.9-4.0 23 lbs/ft3 Red Alder 5.9 28 lbs/ft3
    Silver Maple 6.4 33 lbs/ft3
    Striped Maple 6 32 lbs/ft3
    Sugar Maple 5.1-5.8 44 lbs/ft3
    Sweet Gum 5.2 34 lbs/ft3
    Tamarack Larch 5.2 37 lbs/ft3
    White Birch

(Downy Birch)

5.3-5.5 39 lbs/ft3
Yellow Poplar 5.2-5.4 29 lbs/ft3


*Individual species vary. Specie density may be higher or lower than 45-47 lbs/ft3.

Acidity Source 1:

Acidity Source 2:

Acidity Source 3:

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