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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 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.

SoftwoodsAverage pHAverage Dried Density HardwoodsAverage pHAverage Dried Density
Alpine Fir633 lbs/ft3American Beech5.5-6.245 lbs/ft3
Balsam Fir5.425 lbs/ft3American Black Ash5.534 lbs/ft3
Black Spruce5.728 lbs/ft3American White Ash5.4-6.042 lbs/ft3
Canadian Red Spruce5.527 lbs/ft3American White Elm6.0-7.635 lbs/ft3
Douglas Fir3.332 lbs/ft3Balsam Poplar6.423 lbs/ft3
Eastern Canadian Spruce

(White Spruce)

5.527 lbs/ft3Black Locust5.348 lbs/ft3
Eastern Hemlock5.5-6.228 lbs/ft3American Cherry

(Black Cherry)

Jack Pine5.4American Mahogany5.1-6.737 lbs/ft3
Pacific Silver Fir
(Amabilis Fir)
27 lbs/ft3Chestnut3.630 lbs/ft3
Red Pine5.2-6.034 lbs/ft3Largetooth Aspen5.827 lbs/ft3
Sitka Spruce4.0-5.527 lbs/ft3Oak3.3-3.9*45-47 lbs/ft3
Western Hemlock4.8-5.429 lbs/ft3Quaking Aspen5.426 lbs/ft3
Western Red Cedar2.9-4.023 lbs/ft3Red Alder5.928 lbs/ft3
  Silver Maple6.433 lbs/ft3
  Striped Maple632 lbs/ft3
  Sugar Maple5.1-5.844 lbs/ft3
  Sweet Gum5.234 lbs/ft3
  Tamarack Larch5.237 lbs/ft3
  White Birch

(Downy Birch)

5.3-5.539 lbs/ft3
Yellow Poplar5.2-5.429 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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