Thread: Quartersawn timber movement

Found it on Workshop companion .com
Looks like quartersawn timber expands on half as much as plain sawn timber. See attached

A9D89527-343D-43E1-AE20-EFBDEC77C542.jpg

True enough, but it varies significantly between timbers. For example:

• Huon Pine - 2.5% radial, 3% tangential.
• Karri - 4.5% radial, 10% tangential.

The figures are given in any standard timber reference source such as Keith Bootles book or Wood Database (online).

I'll try to find an article about expansion by Jugo Ilick, formerly of the CSIRO, with a table for common Australian woods. It was published in AWR almost 20 years ago, but I should have a copy somewhere.

One thing about quarter sawn wood is that it tends not to cup as much as back sawn timber.

I should have looked at it before I used some WA She Oak.😩

Quartersawn timber will still extand and contract with ambient moisture levels. The main advantage is that it is less likely to cup which makes is ideal for lids of boxes.

Cheers Peter

Originally Posted by woodtryer

Quartersawn timber will still extand and contract with ambient moisture levels. The main advantage is that it is less likely to cup which makes is ideal for lids of boxes.

Cheers Peter

This be it. Cross the grain, wood expands pretty much equally in all directions, with no expansion longitudinally.

Originally Posted by The Spin Doctor

This be it. Cross the grain, wood expands pretty much equally in all directions, with no expansion longitudinally.

Not true. Most, if not all, timbers expand and contract more in the tangential direction than in the radial direction, and much less in the longitudinal direction. The figures are in standard reference sources.

As woodworkers, we care about wood movement but not the extreme. There are some timbers that start at 30% moisture content, when green, and the shrinkage during drying is significant. But we are not going to start at 30%.

We normally start with dry timber, air dry or kiln dry, 12% or 6%, respectively. Then we allow the timber to reach equilibrium moisture content in our shop for 3 weeks or so. Next, we use the timber to build something. In our building process we allow for wood movement. Will the piece find a home in a Louisiana swamp or an Arizona desert? In either case (air or kiln) the the moisture content change will be somewhere about 2%, if that much. A good finish, especially, on the end grain will retard some of the wood movement.

As woodworkers what do we do? We need to remember that "Wood moves. There is nothing that we or God can do about it."

With apologies for the Imperial system references, I allow 1/8 inch for every foot or 12 inches. There is a trick that can be used to reduce the amount of movement by 50%, sort of. Sliding a panel into a groove I'll put a dab of glue at the center of the panel to hold it in the groove. This means a 1/16 inch allowance is all that is needed but 1/16 on each side. Lacking the glue technique due to pre-finishing, a pin nail gun with 5/8 inch pin-nails may be substituted in the center of the panel.

I response to the OP question; All timber moves. Some species more than others. Shrinkage is evident no matter what configuration sawing has been used. Distortion, on the other hand, is greater in back or rift sawn material than in quarter cut but again, variable between species.

Definition of ‘blank look’ - the look on an assistant at almost any retail hardware outlet at the mention of quarter sawn, rift sawn or similar terms. Rarely followed by the question ‘what’s that’.
Bruce

Dengy

Dimensional change in the length of timber can, fortunately, be ignored for all practical woodworking applications. Completely different matter across the grain as several have already pointed out. Quartersawn timber, if you can get it, is preferred for projects where stability is paramount. There was a time, when windows were made from timber, that quartersawn material was the timber of choice for example.

One way of achieving quartersawn timber is to re-saw your own timber, but this assumes you have large blocks of timber to begin with. Quarter sawn can be up to 45 degs angle on the grain. From any one log only a relatively small proportion can be fully quartersawn.

Timber Milling.jpg

Quartersawing involves additional work at the sawmill, has a lower recovery rate (rustynail, confirmation?) and is therefore more expensive to produce. Consequently, more timber is backsawn or as in the example above, "regular" sawn (probably an American term). Cabinet maker's timbers will be the most likely to have quartersawn availability and then probably only from specialist producers. The pix above ( I grabbed them off the net) would be on a softwood log as the centre portion (heart) of a hardwood log is only waste.

Regards
Paul

Wood movement in response to moisture changes is one of those things that mystifies one at first, but is not very complex, really, if you bear in mind how a tree actually grows.

First rule to remember is that sawn wood will absorb or give off moisture depending on the ambient humidity for as long as it's wood. I commonly read/hear people saying something like, "this has been drying for 40 years, it's totally dry". It will probably have reached equilibrium moisture content (EMC), but it will still contain some water! You can make wood "totally dry" by putting in a drying oven, but if you leave it on the bench for a while it will reabsorb moisture and eventually return to EMC. What % moisture this is depends on the average ambient humidity levels, so it will be different at different times of year or in different climates (you've got a difficult climate in T'ville, bone-dry for 1/4 of the year & tropically humid for another 1/4 and 'reasonable' for the gaps in between the extremes!).

The second rule, as mentioned by other posters is that wood movement in response to water ingress/egress is almost invariably more in the tangential direction of the growth rings than the radial direction & this is the root cause of the 'instability'. This is easy to understand if you bear in mind that a tree grows by laying down new cells only at the periphery - the younger, "fleshier" cells are always toward the outside & there's more of 'em in proportion as the diameter of the tree increases. The inner cells die off, their water levels drop considerably compared with the actively-growing cells and they undergo a bit of shrinkage compared with their younger selves. The walls of these cells also become thicker, tougher, and somewhat compressed. The net result is that they change less in volume as they 'dry out'. There are excellent diagrams explaining this in R. Bruce Hoadley's book "Understanding Wood" if your local library has a copy. Although he uses mainly Nth. American species as examples, the principles apply to any wood.

Putting both rules together, it's pretty easy to predict how a board will react to moisture level changes by looking at the orientation of the growth rings on the end-grain. How much it is likely to move depends on the actual wood and its ratio of tangential to radial movement per unit of moisture change. Woods whose tangential change is much greater than radial will typically distort the most. The only way to know in advance is to look up shrinkage tables for the species concerned. Experience teaches us which woods are the "liveliest", as an old mate used to put it, but unfortunately the test too often comes before the lesson.

The most stable boards typically come from wood that is quarter-cut (or close) and have a tangential to radial shrinkage rate that is similar. Such boards are unlikely to cup, but they will change a little more in thickness in the part of the plank that was closest to the outside of the tree. With a board of 19mm or less thick & not very wide & perfectly quarter-sawn, the difference will be very slight & the board appears to be totally stable.

A very small number of woods have almost the same radial & tangential shrinkage rates, but not all are necessarily 'stable' because of other mechanical properties of the wood, so please don't send a hit-man round to me if you happen to strike one of those exceptions to the rule...

The most likely boards to cup are are those flat-sawn from a wood with a high T/R difference & sawn from the outside of the tree, or close to the outside. On such a board, the growth rings look like a stack of rainbows when viewed from the end. Again, there are exceptions, but if you observe the 'rules of thumb' you will be far less likely to get into trouble, than if you completely ignore them.

Wood does change in response to humidity in the longitudinal direction, but for practical purposes you can nearly always forget about that because the amount of change is negligible except in two situations: The first is if there is significant amounts of sapwood in the board. Sapwood often has quite a high longitudinal shrinkage in response to moisture change compared with heartwood. Fortunately, sapwood is usually easy to see & is usually best avoided anyway, not only because of its mechanical properties but also because it is much more attractive to various wood-munching critters. However, many woods don't have clearly distinguishable sapwood, but fortunately many of these don't have a big difference in longitudinal shrinkage between sapwood & adjacent heartwood & so won't cause you any grief.

The second situation is more annoying & even harder to detect visually & that is significant reaction wood in a board. Reaction wood is the tree's response to prolonged stress in an area (a pronounced lean or a large, heavy branch for e.g.). You often don't know it's there until you start working it - a board may peel apart like a banana as it's ripped, or you notice soft, "furry" areas when you plane it. Reaction wood usually has even more change in response to moisture levels & can produce a lot of tension in a board which can cause you much trouble in a glued-up construction.

If you strike either of these situations, it's best to ditch the offending board & find another because even if you manage to conquer the bowing & twisting, reaction wood takes stains & polishes poorly & you have an even bigger problem trying to finish the item. DAMHIK!

Cheers,

Oh & don't think you can beat wood movement by boxing it in. It can develop an amazing amount of power in response to a marked humidity swing & the thicker & denser the wood, the greater the power!. It may literally tear your construction apart if you attempt to restrain it. I have seen too many examples of self-destruction in pieces that were built without due regard to wood movement. The best example I've seen was a large tabletop made of 55mm thick hardwood, tightly enclosed in a frame about 200mm wide & slightly thicker than the 'panel'. The corners of the frame were mitred, glued with epoxy & had 19mm dowels through each corner. The table was put on a covered deck and in the first wet season the panel blew out two corners, busting the 19mm dowels in the process! I (reluctantly) fixed it for them, making sure there was a good gap to allow the panel to move with the seasons (not ideal on a table top, but necessary in such cases!). That was a good 15 or 16 years ago & I haven't heard that the table destroyed itself again, so presumably the gap was sufficient, but I made no promises!....

Originally Posted by Bushmiller

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Timber Milling.jpg

Quartersawing involves additional work at the sawmill, has a lower recovery rate (rustynail, confirmation?) and is therefore more expensive to produce. ...

Classical explanation, Paul, but have you ever seen a sawmill quartersaw to that pattern? How, for example, would you hold the quarter flitch stably on the saw carriage? And it implies resawing on a primary breakdown saw - a rather wasteful process.

Originally Posted by Bushmiller

...

Timber Milling.jpg

Many moons ago, when I was involved in the timber industry, we tried to optimise the quartersawn production as well as the recovery rate, the grading and sizing rates.

One cutting technique was to produce four "quarter sawing flitches" (*) on the primary breakdown saws [red lines on the drawing] and then send those flitches through horizontal bandsaws to produce quartersawn boards [orange lines on the drawing]. Achieved recovery rates were comparable with backsawing; helped the bottom line.

Flitches.jpg


[* Technically they are flitches rather than billets as they still have a wain edge.]

Graeme, logs were sawn to perfect quarter-sawn patterns - it can be done easily on a "radial" mill that holds the log or flitch and rotates it to the desired position after each pass. This was the more efficient way of getting classic tapered weatherboards, for e.g., though they were also cut from flat boards by re-sawing diagonally. It depended on the sophistication of the mill - the better your set-up, the better your yield, though the actual yield depends even more on the skill & experienced eye of the sawyer and the quality of the log being sawn. Good benchmen were the key to profitable milling....
Cheers,