Processing hickory
May 31, 2014 | 7:00 pm CDT

Q: We have just gotten the word that we will dry and process hickory. Do you have a schedule? Any hints?

A: Hickory lumber consists of four species of "true hickory" (shagbark, pignut, shellbark and mockernut) and four species of "pecan hickory" (bitternut, pecan, water hickory, and nutmeg hickory). In the market place, you can get any of the eight species when you buy hickory lumber. True hickory is found throughout the eastern U.S. However, the range of pecan hickories is limited. Bitternut is throughout the eastern U.S., pecan is found from Texas to Louisiana, through Missouri and Indiana, water hickory from Texas to South Carolina, and nutmeg in the area of Texas and Louisiana.

I think that the true hickory group has more uniform color than the pecan hickory group. Both groups seem to have very nice grain and color character, however, after finishing. True hickory is 10 percent heavier, harder to machine and glue, 20 percent stronger, and shrinks 50 percent more (9.5 percent versus 6.5 percent, green to 6 percent MC) than pecan hickory, on the average. As a result of the higher shrinkage, when yield is measured on the green footage basis, the true hickory group will have 3 percent lower yield.

In terms of drying, we use the same kiln schedule for both groups of species. There is a standard schedule and a schedule for whiter color. All hickory is prone to developing pinking if dried too slowly or allowed to remain tight-piled too long before drying.

Being a dense wood, hickory will require the same care in machining and gluing that other dense hardwoods, like oak, need. Usually, machine tools need to have a larger tool (or sharpness) angle, thereby increasing the amount of metal in the tool. Sharpening may have to be more frequent. Slow feed rates or small depth of cuts will result in rapid dulling. Over-dried wood will be subject to excessive tear-out and even splitting.

When gluing, the edges to be joined must be extremely straight and flat; hickory is unforgiving if the edges are not true. Clamp carriers are probably best for this wood.

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About the author
Gene Wengert

Gene Wengert, “The Wood Doctor” has been training people in efficient use of wood for 45 years. He is extension specialist emeritus at the University of Wisconsin-Madison.