Making the Most of Your Portable Sawmill

By Brett R. McLeod

If you're sawing a relatively large amount of wood, it generally makes sense to separate the flitches into piles based on their approximate width to minimize waste.
Photos by Brett R. McLeod.

Making the most of your portable sawmill begins in the woodlot. As a forestry instructor, one of the most challenging skills to teach students is the ability to imagine what a standing tree will look like as a log and eventually as a stack of boards. This is especially relevant to the portable sawmill operator, who is often the one harvesting the trees prior to milling. This direct relationship with both log and lumber presents the opportunity to minimize waste and increase efficiency. Furthermore, keeping a well-tuned mill and remembering a few simple tips for difficult logs will make your portable sawmilling experience more profitable and pleasurable.

This one-room hunting camp was built using 6-by-6-inch logs sawn by the author using his portable sawmill.

Smart felling and bucking

Cut with a product or purpose in mind. Most portable sawmill owners produce lumber for a specific project. Having a specification list both in the woodlot when felling and at the mill will promote greater efficiency by allowing you to buck to specific, usable lengths and diameters. In general, cutting as short a log as possible (while making sure it's still long enough to meet your needs) will minimize waste, a function of less total taper and less crook or sweep.

Your woodlot is your lumberyard, and as such, a preliminary inventory of your woodlot and a clear harvesting plan will afford the opportunity to match the trees in your forest with your particular needs.

I built a small, one-room hunting cabin using my portable sawmill. Initially, the plan was to use 8-by-8-inch logs, milled on three sides. An inventory of the woodlot revealed an average diameter at breast height (DBH) of only 10 inches. Once taper and sweep were accounted for, it became clear that using 8-by-8-inch logs wasn't possible. Instead, the plan was revised to use logs milled to 6 by 6 inches. In addition to promoting greater utilization of the trees in the woodlot, it also allowed for more efficient sawing by slabbing off 2-by-6-inch boards for rafters while milling the cabin logs. This not only minimized waste, but also increased production efficiency.

Cut low stumps: Up to 80 percent of a tree's value can be captured in the butt log. This is a function of not only the volume found in this first log, but also the grade or quality of the log, which tends to be higher because of fewer knots. This means that a board foot of wood toward the butt of the tree is worth more than a board foot farther up the stem. This increase in volume and value is almost always justifiable, even if it means shoveling snow away from the stump in winter.

While commercial loggers are often forced to work within strict industry specifications, portable sawmill operators can take advantage of "unique" logs that would normally be left behind. Options include intentionally milling logs with a high degree of sweep for specialty applications, such as a curved headboard or curved stringers for an arched bridge. Even short slabs sawn from the root flares of butt logs have found niche markets as artisanal cutting boards.

Not all "defects" matter. One common misconception is that rot or other defects in the center of a log render it useless. As a result, sawyers often "jump butt" or continue cutting away sections of the log until they reach clear wood. When making boards, however, the most valuable wood comes from the "quality zone," which is defined as the portion of the log between the heart zone (the center 40 percent of the log's diameter) and the slab wood (the outer inch of the log's diameter). These high-quality "jacket boards" tend to have large, defect-free areas and capture value that ordinarily would be lost or left behind.

Students in the Paul Smith's College forestry program learn to minimize waste using a portable sawmill.

The well-tuned mill

Keep it sharp: The foundation of a well-tuned portable sawmill is a sharp blade. There is a dangerous and costly tendency to try and get "just one more board" out of a dull blade. The scenario is likely familiar to operators: You push a dull blade just a bit harder to get it into the wood, and because it's dull, you find it diving and rising, making your board thick and thin. Then, just when you think you'll make it to the end, the blade pops off and becomes deeply lodged in the log. At this point, you take out your chain saw and cut off the half-sawn board to release the stuck blade.

This scenario can be avoided by keeping your blade sharp. Pay attention to how the mill is cutting. If you have to tighten the blade frequently, it's probably an indication that the blade is dull (dull blades create friction, resulting in a hot blade that expands).

Make sure your logs are clean and free of foreign objects. If you have access to a garden hose near your milling site, I highly recommend washing the logs and removing any loose bark. The only thing that will dull your blade faster than dirt is hitting a metal object in a log. This is particularly common for yard trees, where nails, old clothesline hooks and fencing are often hidden within the slab layer of the log. A metal detector will quickly pay for itself in terms of both time and blades saved.

The beauty of portable sawmills is their relative simplicity in terms of operation. Fortunately, they are equally easy to maintain. I've adopted a maintenance schedule, based on the manufacturer's specifications, that works well for my mill. I keep a log of all maintenance activities in a waterproof notepad tucked in the glove compartment of the truck that I use to move the mill.

Prior to each use, I inspect the entire mill for loose components. I also check the blade sharpness/tension and all fluids. If you're milling softwoods, be particularly aware of the problems that can be created by pitch. When milling balsam fir, for example, I clean the carriage rails with a lubricant and putty knife every eight to 10 logs. It's amazing how much built-up pitch and sawdust can contribute to uneven/inaccurate cuts. Other maintenance items include lubricating drive chains, flushing hydraulic systems to prevent corrosion, and packing wheel bearings, especially after the mill has sat for extended periods of time.

Maximizing yield

Given that no two logs are identical, it is fair to say that for every sawing rule, there are at least two exceptions. Assuming a relatively defect-free log, I begin by taking a slab off the top of the log, followed by a board or two, depending on what type of lumber I'm making. Next, rotate the log 180 degrees so that the newly created flat side rests on the carriage and remove a slab and board as on the first side. Now rotate the log 90 degrees and repeat the same process on both the third and fourth sides. Once you have a cant (squared timber), you can begin sawing boards off opposite sides.

Milling crooked logs presents several challenges. From a quality standpoint, logs with sweep or a crook bring low-grade heartwood defects to the surface sooner with each successive cut. The result is either narrow or short, low-grade boards with concave or convex faces instead of the long, wide boards found in straight logs.

In general, the most efficient way to saw logs with crook or sweep is to begin by placing the log on the carriage with the ears (sometimes called horns) up. Remove the ears and continue sawing until you have a flat face. Next, rotate the log 180 degrees and remove the sweep slab (hump). You can then rotate the log 90 degrees and continue to saw boards as you normally would.

Ensure efficient edging: No matter how you choose to open up your logs, you'll be left with flitches or unedged boards that you'll want to finish. If you're sawing a relatively large amount of wood, it generally makes sense to separate the flitches into piles based on their approximate width to minimize waste. This means that I routinely have flitch piles that are sorted into 6, 8, 10 and 12-inch groups.

Once the cants have been sawn, I place these boards edge up on the carriage, saw one side, and then the other. If you have just a few boards to edge, you can place them back on the carriage after you've formed a cant, but before you begin slabbing the cant. This way you're able to edge boards and slab boards off the cant in a single pass.

Operating a portable sawmill can be rewarding, particularly when you're able to take credit for bringing the wood from forest to finished product. By practicing wise felling and bucking techniques in the field, performing preventive maintenance on your mill, and studying efficient milling methods, you'll discover that portable sawmills are a practical and profitable forest enterprise.

Brett R. McLeod is an associate professor of forestry and natural resources at Paul Smith's College, located in the Adirondacks of northern New York.