Trade education and workforce development are two initiatives we value highly here at Dunn Lumber, so it should come as no surprise that we have close ties with Seattle Central College's Wood Technology Center (WTC). With roots dating back to the early 1900s, WTC's history intersects with ours at Dunn Lumber at various points (our very own Ed Dunn Jr. took some classes at Edison), and we're proud to be connected with such an exemplary educational institution.
Throughout the episodes in this series, we'll be speaking with Dave Borgatti, a long-time faculty member at the WTC, about the center's history, program offering, and various topics in woodworking education. Dave got his start in woodworking as a boat builder in Portland, Oregon, for Schooner Creek Boat Works, and ended up at WTC as an instructor in 1992. Since then, Dave has helped countless students—from boat builders to carpenters and cabinetmakers—learn the woodworking craft.
In today’s discussion, Dave and I go over why it’s important to start with “clean wood,” how to prepare wood for machining, and the process of taking rough lumber and turning it into surfaced lumber, or S4S.
Watch our discussion in the video above, or keep reading for a detailed recap.
What is the difference between rough lumber and surfaced lumber?
Most of the wood products you'll see at the lumberyard are “dressed” or surfaced four sides (S4S). This is very different from the sawmill, where the wood is rough, fuzzy, and shows bandsaw or circular saw marks. Anyone working exclusively with hardwoods (custom woodworkers, cabinetmakers, boatbuilders) will buy material in this rough stage where the thickness is measured in quarter inches (see our previous episode on nominal versus actual lumber sizing). But even the wood in a lumberyard has defects such as bow and crook and can be flattened and straightened using the techniques listed below.
How to surface rough lumber
Step 1: Clean the wood
Inspect the wood for staples, dirt, or nails and remove so as not to damage the knives on the thickness planer. Anyone who uses a thickness planer can tell you what a pain they are to change—but you may have to do just that if you forego this first step. The blades of a thickness planer, while sharp, are very brittle. Also, the new table saws have flesh-detecting technology, which relies on electrical conduction, and embedded metal can set these blade brakes off.
Wood stains can often show bits of metal like bullets or barbed wire as well, so you may need to use a chisel, staple puller, or wire brush to remove those hazards.
Step 2: Inspect and resize
The second step is looking at the board to see which areas are useable. Straight grain may be easy to work with, but knots and wood figure can be more attractive. Woodworkers have to determine whether to “feature” a knot or eliminate it. Additionally, smaller pieces are easier to machine, so this is the time to reduce the length and width to a manageable size.
Step 3: Joint a face
The jointer is the first tool that actually flattens a board’s face. (The planer gives the wood a smooth face but doesn't flatten the board.) If the wood is really rough, you can set the machine to take off up to 1/8" of material, but as it gets flatter, each pass should take off no more than 1/16”. The result is S1S, or surfaced one side.
Step 4: Plane the opposite face
Next, the freshly jointed wood goes to a surface planer to plane the opposite side. You can run it through repeatedly to bring the material to the desired thickness. Be careful to flip the board end for end with each pass so the moisture content will be similar on each face. The result is S2S, or surfaced two sides.
Step 5: Joint an edge
The jointer has a fence which is normally set to 90º in order to “square up” an edge. When this is complete, the wood is considered S3S, or surfaced three sides.
Step 6: Table-saw the opposite edge parallel to the jointed edge
If you take the material in Step 5 and simply flip it over, the result will not be parallel—so this step is crucial to getting straight and even edges. However, the result here is still not S4S but rather S3S with a sawn edge.
Step 7: Joint the sawn edge
Finally, we return to the jointer for a last (generally light) pass to both square the material and remove any saw marks. Now you have true S4S, or surfaced four sides. In the trades, this wood is often called “four square.”
Safety concerns and limitations when surfacing wood
While planers feed wood automatically, and table saws have guards, splitters, and flesh-detecting brakes, the jointer is a completely different tool. The guard retracts as you push the material through and the spinning cutter head is just beneath your hands (so be sure to use push pads, blocks, or push sticks to keep your fingers from getting anywhere near the knives). These tools get more expensive as they get wider: An 8" jointer is more than double the cost of a 6" jointer. If you need to joint really wide boards, consider a trip down to your neighborhood cabinet shop.
Be sure to check out the introduction to the Wood Technology Series. For more information about different types of wood, check out our breakdown of plain-sawn, quartersawn, and rift-sawn wood.