In the Missouri Ozarks, there is a plethora of tree species to keep things interesting at the sawmill. Technically the forest is classified as oak-hickory, but the nine species of oak and four species of hickory don’t begin to describe the diversity. Sycamore, walnut, cherry, sassafras, persimmon, sweet gum, pecan, elm, mulberry, honey locust, Osage Orange, ash, and hackberry all grow in this part of the country. While hardwoods dominate, there are enough softwoods—eastern red cedar and shortleaf pine—to provide an incredible variety of woods to mill. Your part of the world may likewise be home to several interesting types of wood. Each species has its own properties and milling requirements. There can be a great deal of variety between species. By keeping your portable sawmill in good working condition, your bandsaw blades sharp and arming yourself with a variety of sawing tricks, you’ll never be defeated by a log (unless maybe it has a railroad spike in it).
One would expect softwoods to cut more easily than hardwoods and they generally do. But not all “softwoods” are soft and not all “hardwoods” are hard. Southern yellow pine, for example, is actually harder than basswood. There are a few general rules of thumb to help you deal with the wide variety of logs, which may come your way.
Softwoods generally cut easily, which allows you to use a blade with an aggressive cutting angle of 10o. These blades can plow through the relatively soft wood fibers easily. If you find the blade wandering on easy cuts, try increasing the feed rate. On cuts over 10” wide, you will need to slow the feed rate a bit in order to keep the gullet (the area between the teeth) from filling with sawdust before it clears the edge of the log. Otherwise, excess sawdust in the gullet will spill out around the blade and cause a wavy cut. The best measure is to watch the amount of sawdust coming out of the sawmill chute.
One of the most troublesome problems with cutting softwoods is the buildup of pitch on the blade. The extra friction caused by the pitch on the blade makes your engine work harder and causes the blade to heat up. In extreme cases, you will actually see smoke coming out of the cut. Heating the blade to this point can soften the metal so that it will not hold an edge after sharpening. The best way to deal with pitch buildup is to add cleaning fluids to the blade lubrication. Experienced sawyers have recipes they swear by, but I have found that adding ¼ cup of a cleaner such as PineSol and ¼ cup of Simple Green per gallon of water will keep a blade clean; it doesn’t take much. Start out with a drip feed and increase it a bit, as necessary.
There is a lot a variation in hardwood logs. Your sawing strategy for these woods will depend on how hard the wood actually is, the width of the cut and the power of your portable bandsaw mill engine. For the softer species—basswood, sycamore, poplar, soft maple, butternut and walnut—the blade type and cutting speeds will be similar to that for softwoods. Harder woods, such as red oak, ash and cherry offer more resistance to cutting. A blade with a less aggressive angle may work better, especially with lower horsepower engines. If you hear the engine speed drop while cutting, slow down the feed rate a bit. With the hardest woods – including white oak, black locust and hickory – an even shallower blade angle may help. Keep a few 4° blades on hand if you plan to work with any of these species. With the slower feed rate these species require, you may notice some blade vibration. Closer tooth spacing, such as a ¾” pitch blade, will usually solve this problem. Pitch buildup may again be a problem with some hardwoods during spring when the sap is rising. The same lubrication that works on the softwood logs will take care of this.
Several hardwood species merit special attention. Hickory and pecan (both in the same family) are notoriously hard to cut! On some cuts, you could swear the saw blade has mind of its own as it goes everywhere but straight. With these species, it is especially important to keep a sharp blade on the mill. You may need to change the blade after only a couple hundred board feet. The 4° blade angle, ¾” pitch blade is generally your best option for this type of wood. When cutting these species, you may also need to crank a little more tension on the blade than you normally use. Cottonwood, although soft, tends to produce fibers that drag against the blade, which heats it up.
No matter what species you work with, it is generally better to mill the wood as soon after the log has been cut as is practical, which is one of the great advantages of owning a portable bandsaw mill; with “portable” being the operative word. You can take the mill to wherever the logs are being cut. Many species, such as pine, aspen and hickory begin to decay within a few weeks. As hardwood fibers dry out, they become more difficult to cut. Milling will be slower and the blade will dull more quickly. End checking (cracks) in a log, which has not been milled right away, may reduce a 10-foot log to an 8-foot log; and no one wants to waste valuable lumber.
Keeping your blades straight generally requires some organization. You can use different color plastic zip ties—green for 10° angle, yellow for 7° and red for 4°. Consider buying 10o blades and then grinding/sharpening a few to 7° and 4° for the particularly tough logs. If a log is not cutting straight, the first thing to do is put on a fresh blade. You may have hit some grit in the bark or otherwise dulled the blade without realizing it. Mill setup is the other common cause of cutting problems. Be sure to follow the portable sawmill manufacturer’s instructions for aligning the mill and setting the blade guide blocks or rollers.
Finally, keep notes on what works and doesn’t work for any particular species of wood. If you find a particular combination that is perfect for walnut, write it down. And be sure to also post it here on Trees2Money, so that other sawyers can benefit from your experience.
Tree Diversity Maps courtesy of http://www.seesouthernforests.org/gallery/maps/28-southern-forests-center-biodiversity-trees