Quartersawn lumber moves less across its width than flat-sawn lumber because its width runs in the radial direction, and wood shrinks and swells less radially than tangentially [1][2]. The gain from quartersawing is largest in species whose tangential movement is much larger than their radial movement, such as hard maple [1].
Two directions of cross-grain movement
Wood has two cross-grain shrinkage values. Tangential shrinkage runs along the growth rings and is the larger value. Radial shrinkage runs across the growth rings, from pith toward bark, and is the smaller value [1].
The width of a flat-sawn board runs roughly tangential to the growth rings, so flat-sawn width moves at the tangential rate. The width of a quartersawn board runs roughly radial, so quartersawn width moves at the radial rate [2].
Hard maple (sugar maple) shrinks 9.9% tangentially and 4.8% radially from green to oven-dry. Its T/R ratio, tangential divided by radial, is 2.06 [1].
Because hard maple's T/R ratio is 2.06, a flat-sawn hard maple panel moves about twice as far across its width through the seasons as a quartersawn hard maple panel of the same width [1][2].
The T/R ratio of a species indicates how much quartersawing helps. Quartersawing reduces panel movement more in a high-ratio species than in a low-ratio species [1].
Among black walnut, black cherry, white oak and hard maple, hard maple has the highest T/R ratio, 2.06. Black walnut has the lowest, 1.42 [1].
Quartersawing matters more for hard maple than for black walnut, because hard maple's T/R ratio of 2.06 is well above walnut's 1.42 [1].
Density and dimensional stability are different properties. Hard maple's density and fine grain make it seem stable, but its tangential movement is real and larger than its reputation suggests [3].
Panel width and the case for quartersawn
Seasonal movement across a panel is proportional to the panel's width, so the case for quartersawn stock grows with panel width and with the species' T/R ratio [1].
A wide flat-sawn panel in a high-ratio species can still be built successfully. It needs larger float clearances, wider slots, longer breadboard slot elongation and attachment designed throughout for the full flat-sawn movement [1].
Ray fleck
Medullary rays are ribbons of cells that run radially from the pith toward the bark. A quartersawn face cuts along the rays and shows them as ray fleck, the distinctive shimmer in quartersawn white oak and a subtler glint in hard maple [1][2].
Ray fleck is physical evidence that a board's face lies near the radial plane [2]. A board sold as quartersawn that shows no fleck at all deserves a closer look before it is accepted as quartersawn.
Arts and Crafts makers such as Stickley and the Greene brothers used quartersawn white oak because the style's wide, plain surfaces needed stability. The ray fleck came with the cut [1].
Rift-sawn lumber
Rift-sawn lumber is cut so the growth rings meet the face at roughly 30 to 60 degrees, between flat-sawn and quartersawn [4].
Rift-sawn movement falls between the tangential and radial values. For hard maple, the rift value is about 7.4%, the average of 9.9% tangential and 4.8% radial [4].
Rift-sawn stock shows straight grain on all four faces of a square piece, without the cathedral pattern of flat-sawn or the heavy fleck of quartersawn. That is why rift-sawn stock is the traditional choice for table legs, where four matched faces must look alike from every angle [4].
Sourcing quartersawn stock
Quartersawn hardwood is not routinely stocked at general-purpose lumber yards in British Columbia. It usually comes from specialty hardwood suppliers, sometimes in limited runs, so a call ahead saves a trip [5].
Mail-order quartersawn stock from United States specialty dealers is an option for British Columbia buyers, with duties and shipping time added to the cost [5].
Quartersawn lumber costs more than flat-sawn lumber because a log yields less of it [5]. Quartersawn stock is best ordered before the rest of a project's materials, not in the week milling is planned.
The decision is made at the lumber yard
The choice of cut is made at the lumber yard. Once flat-sawn boards are in the shop, the decision has already been made.
Two questions settle the choice at the yard: how wide is the widest solid-wood panel in the piece, and what species is it. A wide panel in a high T/R species such as hard maple is the clearest case for specifying quartersawn stock [1].
Quartersawn is not a premium finish. It is a cut that puts the smaller movement value across the width that matters [1][2].
Sources
- USDA Forest Products Laboratory, Wood Handbook: Wood as an Engineering Material (FPL-GTR-190), Chapter 4, Table 4-3 (Shrinkage Values); Hoadley, R.B. (2000), Understanding Wood: A Craftsman's Guide to Wood Technology, 2nd ed., Taunton Press, Chapter 4.
- USDA Forest Products Laboratory, Wood Handbook (FPL-GTR-190), Chapter 4; USDA FPL-GTR-113, Chapter 3 (as listed against Hewn heuristic R759 in Hewn's notes).
- Hewn heuristic data, HEU-R1234 (hard maple stability reputation), Reed Additions, provisional and unreviewed.
- stephan-woodworking.com, "Quarter Sawn, Rift Sawn, Flat Sawn"; woodworkerssource.com, "Wood 101: Flat, Quarter, and Rift Sawn"; popularwoodworking.com, "Rethinking the Common Board"; USDA FPL-GTR-190 for the T and R values averaged (as listed against Hewn heuristic R762 in Hewn's notes).
- Hewn heuristic data, HEU-R763 (BC quartersawn sourcing), unreviewed, with the supplier listings and the woodweb.com "Quartersawn lumber sources" forum it was checked against.