In this blog, we walk you through our sawmill and discuss how lumber is produced in large quantities.
Although it’s not in our video, the first step of sawing logs into lumber is removing the bark at the debarker. Removing the bark does a few different things. The first is it helps show what the log actually looks like, meaning more defects can be seen on the log once the bark is removed. This helps the sawyer at the headsaw determine where to take his first cut.
Removing the bark also helps remove any dirt, mud, rocks, sand, and other sorts of things that might be hiding in the bark. The bark is sort of like a protective layer for the timber. Trees might get cut in mud, and logs are normally stored on gravel, sand, or dirt. But dirt, rocks, mud, and sand are all very abrasive on tooling and quickly dull blades. The faster the blades dull means the more they have to be sharpened and replaced.
Once the bark is removed, the debarked log goes to the headsaw.
The main purpose of the headsaw is to take the circular log and cut four sides on the log. This four sided log is called a cant. The headsaw can also cut boards off of the cant, but here at our sawmill, we only square up the log into a cant.
There are two main types of headsaws: circular saws and band saws. They both have benefits and downsides, things like size, initial cost, costs of tooling, and available space. But one of the biggest factors is the size of the kerf (thickness of the blade). The larger the kerf, the more sawdust will be made, which means less lumber produced from that tree. Circular saw head saws tend to have a ¼” kerf while bandsaw headrigs usually only have an 1/8” kerf. We have a circular saw headsaw, which is why we only square up the log at our headsaw. Because we only make a cant at the headsaw, no extra material is lost by the size of the kerf.
At this point, the cant is transferred to the resaw.
At the resaw, the cant is sawed into boards. There are a couple different styles of resaws, but each style accomplishes this task. We have one 6’ line bar resaw and one 54” band saw resaw. Either a grader or the resaw operator will look at all four sides of the cant to determine which face has the highest grade. Then the operator saws a board off the highest grade face of the cant.
The boards that were cut at the resaw are sent to the edger. At the edger, the board’s edges are trimmed. They are edged for a few different reasons. The first is it simply makes boards more presentable. No one likes a board with a ton of wane (bark), so removing this wane makes the board more desirable.
The other reason is because of grade. The National Hardwood Lumber Association (NHLA) has a set of lumber grading standards. Within these standards, there are rules and limitations of what can be allowed in a certain grade. For the upper grades (Select, F1F, and FAS), there are wane limitations stating how much wane can be on a board. So by edging board, you can possibly turn a #1 Common board into an FAS board which increases the board’s value.
Although you don’t see it in our video, after the boards are edged, they are transferred to the trim saw. The trim saw cuts boards to length. In the hardwood industry, it’s standard to leave 4” of overlength on a board. This is to help account for any end splitting or checking that might occur during the drying process. So even if a board is sold as 8’, chances are it is actually 8’ 4”. But a board only needs to be 8’ long to be sold as an 8’ board.
The other reason boards get trimmed are for the same reason boards get edged: it dresses up the boards and makes sure they are the best grade they can be. Just like wane, splits also have limitations within the upper grades.
After the boards have been processed, they need to be graded. The graders grade boards based on the NHLA rules. Every species has its own rules of what is allowed and what isn’t in specific grades. Even though they make it look easy, it takes years of training and practice to be able to grade at the speed of production.
Now that the boards are graded, they are transported on the green chain. Here you will find people piling down the boards by grade, thickness, and species to create a pack of lumber.
As you might have noticed in the video, every time you further manufacture a board, waste is created. This waste isn’t just thrown away though. Our sawmill is set up in two levels. The floor you see in the video is the manufacturing floor. But if you go back and watch closely, you will notice slab pieces and edge trimmings going to the lower level. The lower level consists of conveyors that lead to a chipper. The chipperr turns the edgings and slabs into chips, and the chips are sorted out by size. The larger chips go to paper manufacturers and are used for fuel during the paper making process. We keep the smaller chips in house and burn to heat our boiler for our kilns.
The second kind of waste is sawdust. We sell our sawdust to companies to use for food flavoring and cleaning compounds. But sawdust is also sold for animal bedding and to wood pellet making manufactures.
Bark is the last waste. Once again, no part of the log goes to waste. We sell all of our bark to landscaping companies to get processed into mulch.
After the lumber is piled off the green chain, the packs need to be stickered and then dried in kilns. Within the next couple weeks, we will be taking a tour through our stickering and kiln drying departments. Stay tuned!