Ask any four sawyers the best way to cut a log and you’ll likely get at least a dozen different opinions. Often the disagreement comes because they use different terms to describe exactly the same procedures. To add to the kerfuffle, some of the terms are contradictory. There are also many variations to cutting patterns depending on the log and the end use of the lumber. However, sawing comes down to 6 basic log sawing patterns: rift sawing, plain (or flat) sawing, grade sawing, sawing for character, slabbing and quarter sawing.
Rift sawing produces 100% true quarter sawn lumber. This sounds good, until you see how much wood it wastes and it is nearly impossible to rift mill on a portable bandsaw mill or circle mill. You will probably never actually rift saw a log, but you will likely hear the term, so it is good to at least know what it is. Rift sawing involves rotating the log after each cut so the boards are sliced in a radial pattern. This pattern was once used to quarter-saw white oak for whisky barrels, back in the days when the staves were split by hand. Here is an illustration of a rift-sawn log. No wonder we don’t do that anymore!
Plain sawing is a straightforward process and is the fastest way to slice up boards. Basically, the log is squared to a cant and the sawyer mills the boards straight down to the bottom. Off-center pith is a major cause of drying defect. For quality lumber less prone to warping, keep the pith (center of the growth rings) centered, since the wood around the pith has different shrinkage properties and can cause the board to warp. A trip to the lumberyard will verify this—just look at the end of any warped board and you will likely see off-center pith. The simplest pattern is to square the cant to the width of the desired boards, then mill straight down. If you have a wide cant, you may be able to cut multiple boards with each pass. If possible, mill an odd-number of boards (one or three) at a time, in order to keep the pith centered in the center board. If not possible, edge the boards to remove any wood that comes within 6 growth rings of the pith.
Grade sawing improves the value of the wood by putting as many defects as possible in as few boards as possible. This is more common in hardwood lumber where random widths are allowable, but can be used with dimension lumber if the sawmill operation has access to an edger. Again, the log is squared into a cant, but rather than aiming for a certain width, the sawyer cuts the best face of the log until the quality diminishes to the point where another face would yield higher grade lumber. The process of turning the cant to always be cutting the best face can increase the value of a log by as much as 20%. On the downside, all of the log turning takes extra time and effort, especially on manual sawmills. This pattern is most useful for lumber to be sold to cabinet shops, flooring mills and other end uses, where grade is important. If the customer is a woodworker who wants “character” boards, you should consider sawing for pattern.
Sawing for Pattern
Sawing for pattern is the same, in principle, as sawing for grade. Look for the side of the cant with the most interesting pattern and mill this side until the pattern runs out, then turn the cant to find the next side with the most desirable pattern. Note, “character” is not always the same as “defect”. You should balance out the desire for character with the need to keep splits and rot in as few boards as possible. The advantage of sawing for pattern is it gives the owner the opportunity to “bookmatch” boards to give tabletops and other large surfaces mirror-image symmetrical grain patterns.
Slab sawing is the simplest pattern—just mill the log about half way down, flip it over and finish the other half. It yields the widest possible boards and provides natural edges for woodworkers who build custom pieces. One of the issues you may run into is the width of the log may exceed the capacity of your sawmill. If this is the case, you may need to slab off one side, then turn the log 90 degrees to slab it. The rule of thumb for slab thickness is 1/10th the width. A 20” wide slab, for example, should be at least 2” thick.
A lot of people ask for quartersawn lumber without even understanding what it is. Quartersawn (also called “vertical grain”) boards have growth rings running perpendicular to the surface of the board. Anything between 70 degrees and 90 degrees is considered quartered or vertical grain. No matter how you mill a log, there will be some quartersawn boards in the stack. If you set your quartersawn boards aside in a special pile, you may find you can meet the demand without special sawing and you will get a premium price for your efforts. While it is true quartersawn lumber is less prone to cupping and is more stable than flat-sawn lumber, the real appeal is for species like oak and sycamore, in which the ray cells give the board a distinctive pattern. Craftsmen building mission style furniture, for example, usually specify quartersawn oak for tabletops and bench seats. There are some things you can do to maximize the amount of quartersawn wood out of a log, though they do take more work.
The simplest pattern is to quarter the log, then put each piece back on the mill, one at a time and cut it in a pattern keeping the grain as vertical as possible. This involves a lot of turning and clamping. If the log is too big to quarter on the sawmill, you can either quarter it with a chain saw or square it up before quartering.
Another option is to cut some wide slabs out of the center before getting to the cut-and-turn quartersawing pattern. As you mill the two halves, pay close attention to the grain and turn the log to the face producing the closest to a vertical grain pattern.
The ultimate goal should be to produce lumber your customer wants (and will pay a premium for) with the least effort and waste. Knowing different cutting patterns is like having different tools in your toolbox. Every sawmill is different, but with time and experience, you will gain the tools, techniques and the reputation for providing your customers with reliable, high quality lumber, which they can in turn use to create beautiful furniture or other items.
Let us know if you have learned any other tricks or tips you can share for getting the right cuts from your logs.