Quartersawing, Mining for Gold
Bob Hoffa
This article describes the process we use at Alta Resource to quartersaw a hardwood log, and explains the differences between plainsawn and QS (quartersawn) lumber.
QS Defined
If one were to put a log on the mill and saw it into boards without moving the log, the result would be both plainsawn and QS boards. As shown in the picture below, the QS boards (on the left marked A) would come from the center of the log, where the rings of the tree are oriented from 45 degrees to 90 degrees to the surface of the board. In the plainsawn boards (on the right marked B), the rings are oriented from 0 degrees to 60 degrees from the surface. The plainsawn boards would be the first and last ones off the log.
Plainsawn and quartersawn boards from the same log.
A log can be sawn in such a way as to yield all QS boards. While more wasteful, the value of the wood is enhanced. Certain trees deserve the additional effort of quartersawing to reveal grain patterns and board stability not available when production plainsawing is done. When an exceptional log comes into the mill we always consider quartersawing.
The Advantages of Quartersawn Wood
- It shrinks and swells less in width.
There is less cupping and twisting.
Fewer checks and splits in use or while drying.
It wears more evenly.
Some figure is more pronounced, such as rays, wavy and interlocking grain
Sapwood is limited to the edge of the board.
The Disadvantages of Quartersawing
- There is more wood waste.
Because of waste, QS lumber is usually more expensive.
Spike knots are more likely.
Shakes or pitch pockets extend through more boards.
It may shrink and swell more in thickness.
The Tree in our Example
The tree shown here was a storm fallen White Oak of monumental proportions. It was 256 years old when it toppled and 42" at breast height, a mere sprouted acorn in 1742. It took until 1801 for the tree to reach 40 feet in height.
The average whole tree ring frequency was 13.2 rings per inch with a growth release observed in the rings around 1870. The pure stand grove was probably partially cleared at that time. The reason it gave up standing was probably due to cattle grazing thus compacting the soil and stomping on the roots. Root ball degrade followed and finally could no longer hold up the 15 tons of wood. A total of 40 linear feet of main trunk was salvaged and quartersawn.
Quartersawing Shown Step by Step
The First Cut of the Whole Log
It is called quartersawing because the log is divided into 4 quarters and each quarter is sawn separately. Each quarter is roughly squared up and rotated to yield boards with the desired grain angle.
To quartersaw a log it must first be aligned on the mill so the pith (center axis) is parallel to the saw bed. Then a nerve racking halving of the log is done with the horizontal bandmill blade sometimes involved with 45" of hard white oak end grain. If the blade broke in the middle of this log, it would certainly be a bummer. Wedges are employed near the end of cut to keep the 2000 pound half log from pinching and possibly stalling the band blade.
Sorry there’s no photo of this cut, I was much too nervous to hold a camera.
From Half to a Quarter
The log is now a half of a cylinder, and is clamped with the flat side vertical . The blade height is again set to cut through the pith, which is the heart of the tree. This half is slightly narrow because the pith was not in the center of the log. Once again, wedges are employed before the end of cut to prevent the blade from being pinched.
The second cut takes the log from half to quarter.
First Quarter; The Pith Cut
This first prep cut on the log quarter removes the pith and any defects associated with it. It also provides a straight, flat reference for the next cut.
The first cut on the quarter removes the pith.
First Quarter; The Slab Cut
Shown below, the quarter is flipped 180 degrees. A back, or slab cut is made parallel to the pith cut and gives you a straight edge for the center boards. This cut also determines the maximum width of boards where the strictest vertical grain wood is derived. When this slab cut is clamped vertically, it provides a reference for the next cut. The boards from this quarter will be 13" wide and 9 feet long.
The quarter has been turned 180 degrees with the pith cut down for this next cut.
First Cut First Edge
The quarter now has two parallel straight edges, and is turned 90 degrees on the bed of the mill (shown below left). The blade height is set to make an edge cut where the wood is 4" wide. This will be the narrowest board. Following this first edge cut, 4/4 (or 1" thick) boards are sliced, becoming ever wider and showing more vertical grain. We obtained 6 boards ranging from 4' to 12" wide, with 50 to 80 degree grain angles respectively before stopping just short of the premium, wide center section of the quarter (below right).
For the first edge cut the quarter is rotated 90 degrees with the slab cut perpendicular.
Last Cut on the First Edge
When we get close to full width boards on this quarter, we stop just short of entering the most premium wood in the cant (below). The cant is rotated 180 degrees for the next cuts.
The last cut of the first edge stops short of the premium wide section.
For the first edge cut the quarter is rotated 90 degrees with the slab cut perpendicular. The last cut of the first edge stops short of the premium wide section.
The first board comes off the second edge.
When sawing 4/4 (or 1") material, the first cut is made at some multiple of 1-1/8" (1" for board, 1/8" for blade kerf). This allow the last board to be full unless springing of the cant occurs.
The Premium Zone
This is the most rewarding area of the original cant. Hopefully we’ll produce four or five 13" wide CVG (or clear vertical grain) boards. This time we opted to also produce one 8/4 CVG for marine boat building use since all the quality specifications were there. That board was the last one left on the mill by not making another 4/4 cut. The actual dimension is 2-1/8 thick since the kerf was added back.
Perfectly quartersawn white oak board.