Hardness ratings help you choose the right species   

Here’s the business end of an Instron wood-hardness testing machine. The sample beneath is Douglas fir.

Q:

I’m building a workbench that will, of course, take a lot of abuse. That started me wondering about the relative hardness of different woods. How is that determined, and how do the popular woodworking species rate?   
—Dale Glesser, Lorain, Ohio

A:

A procedure called the Janka hardness test provides the answers, Dale. Using a powerful press and a steel ball with a diameter of .444", technicians measure the force required to sink half the ball diameter into the face grain of a wood sample. The resulting number, expressed in pounds of force, determines the hardness rating of the species. Listed in order of increasing hardness, here are the results for a few wood species, as tested at 12-percent moisture content.

wood species chart.jpg

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