Quartered sawn wood In guitar making on many top end guitars, is of paramount importance for structure, sound, strength and aesthetics.
Quarter sawing is a type of cut in the rip-sawing of logs into lumber. The resulting lumber is called quarter sawn (quarter-sawn), quartered, and radially-sawn.
Quarter-sawn boards have greater stability of form and size with less cupping, shrinkage across the width, shake and splitting, and other good qualities. In some woods, the grain produces a decorative effect such as oak which shows a prominent ray fleck and Sapele Mahogany is likely to produce a ribbon figure
When boards are cut from a log they are usually rip cut along the length (axis) of the log. This can be done in three ways: plain-sawing (most common, also known as flat-sawn, bastard-sawn, through and through, and tangent-sawn), quarter-sawing (less common), or rift sawing (rare).
In flat-sawing the log is passed through the blade cutting off plank after plank without changing the orientation of the blade or log. The resulting planks have different annual ring orientations when viewed from the end. The relative angle that form the rings and the surface go from almost zero degrees in the external planks to almost ninety degrees at the core of the log.
Quarter sawing gets its name from the fact that the log is first quartered lengthwise, resulting in wedges with a right angle ending at approximately the centre of the original log. Each quarter is then cut separately by tipping it up on its point and sawing boards successively along the axis. That results in boards with the annual rings mostly perpendicular to the faces. Quarter sawing yields boards with straight striped grain lines, greater stability than flat sawn wood, and a distinctive ray and fleck figure. It also yields narrower boards, because the log is first quartered, which is more wasteful.
Quartersawn boards can also be produced by cutting a board from one flat face of the quarter, flipping the wedge onto the other flat face to cut the next board, and so on.
Quarter sawing is sometimes confused with the much less common “rift sawing. In quartersawn wood, only the centre board of the quarter-log is cut with the growth rings truly perpendicular to the surface of the board. The smaller boards cut from either side have grain increasingly skewed. Riftsawn wood has every board cut along a radius of the original log, so each board has a perpendicular grain, with the growth rings oriented at right angles to the surface of the board. However, since this produces a great deal of waste (in the form of wedge-shaped scraps from between the boards) rift-sawing is very seldom used. Quartersawn wood is thus seen as an acceptable compromise between economical but less-stable flatsawn wood (which, especially in oak, will often display the distinct “cathedral window” grain) and the expensively-wasteful rift sawn wood, which has the straightest grain and thus the greatest stability.
Quartersawn boards have two advantages: they are more resistant against warping with changes in moisture and, while shrinkage can occur, it is less troublesome.
In high-end string instruments, the neck and fretboards can be made from quartersawn wood since they must remain stable throughout the life of the instrument, to keep the tone as invariable as possible. In acoustic guitars, quartersawn wood is also often used for the sides which must be steam bent to produce compound curves and the soundboard. The soundboard particularly, is often made from quarted Spruce or Cedar to enable the best sound consistency and strength. The strength (flex) will be more along the length (with the grain) of the top, and the braces will support the width. (In violins, wedges are split from a specially selected log to ensure vertical annular rings). This is mainly for structural reasons, but also for the aesthetics of highly figured timbers being highlighted when sawn this way. On high-end acoustic, electric and bass guitars quartersawn wood is often used as the base material for the neck of the guitar, since this makes for a stronger and straighter neck which aids tuning and setup stability.
The second advantage of quartersawn wood is the decorative pattern on the board, although this depends on the timber species. Flat sawn wood (especially oak) will often display a prominent wavy grain (sometimes called a cathedral-window pattern) caused by the saw cutting at a tangent to a growth ring; since in quartersawn wood the saw cuts across the growth rings, the visible grain is much straighter; it is this evenness of the grain that gives quartersawn wood its greater stability.