I've used this tool you mention, yet no one was able to tell me the name of it.
A small brass device that flips open and has a little nail on the tip.
I was told in grading that it measures the 'slope' of the grain, and will not detect spiral checking...

I have to remember to take more pics, for today I had the perfect example of a straight grained larch timber with said spiral checking, which I come across sometimes.

Too bad I have a 3 day weekend and I'm not going to be at work tomorrow..sitting on the beach instead ....

Yup, that's the tool, I don't know the name either, they showed us in a grading class how to use it.

here's how I understand checking; As the timber shrinks, the drying shell is shrinking around a still green and swollen core. When this drying stress exceeds the woods strength perdendicular to grain, it splits. Wood is far stronger with the grain than perpendicular to it. What I think you are proposing is that the wood is splitting diagonally across the length of the cells. The picture I'd like to see would be to cut a firewood length of the checked larch then to split the firewood right beside the check to show the grain orientation. I hope we can agree that firewood splits with the grain? I'll bet the check and the split is in the same plane, the wood will not split across the check.

That said I can think of a notable exception where I often see cross grain breaks at 90 degrees to the grain, across the board.
When we lay 5/4 southern pine decking. The decking is often made from heart pieces that include juvenile wood. When we screw the board down it is restrained from bowing. The mature wood alongside of the juvenile core restrains the wood also. It is pretty common to see an unrestrained piece on a pile bow like crazy. It is also common to see a piece screwed down on a deck checked, cross grain in the juvenile zone as that wood shrinks lengthwise. That is not what we're talking about here though, they are graded as "compression failures" or "timber breaks" and are limited to the lower grades.

What you are proposing would stand grading on its head, its opposed to I was taught in grading school and have seen in my experience. If you can get tension perp failures in the grain direction, we got biiig problems That is another thought. How many are using accredited graders as required by code in most places? Should the Guild be having graders teach sessions at events? The '06 code has tightened up a notch on that front, that will only continue.

I don't entirely disagree with you, believe me, but that is the way its heading. But, checking does show the direction of the true "grain" of a piece of wood. When you split that piece of checked firewood I can about guarantee it will cleave in the plane of the check, that is how the timber will fail. If you see a diagonal check across a timber, measure the slope of that check and use that as the slope of grain in determining the allowable stresses that the engineer will use in determining the timber"s strength. These are sympathetic jobs not an either or, a good grading gives the engineer what he needs to design safely.

As far as whether to trust the TPI grader, or the engineer... I'd rather you were trained and approved to gradestamp your own At the end of the day, after you have worked the timber, that is the true grade. You are ultimately the grader no matter what the timber was to begin with. If the engineer assumed a #2 strength and you gave him a timber with #3 sloped checks, the timber is weaker than designed. A mortise across from a knot could weaken the timber more than intended, or not, knowing the allowables lets you keep the strength up to the engineer's assumptions. I attended TPI's grader training class, and feel I did bring more to the table than many of the "real" graders that are on the line stamping what I cull around at the sawbench every day. I can't change that, the training did give me a better eye, I learned alot. I think it is worthwhile for a woodworker to know the rules and the whys. Being well trained as a group might help when your local enforcement of these codes tightens.

i've been curious about the distinction Phleps makes between "left hand' and 'right hand' spirals, where a clockwise spiralling grain (looking up the tree) "should be rejected for building purposes" ??!!!1 how could this matter? more checking? twisting? white spruce with spiral grain does seem to check big. of the two big checked logs in our house (white pine) one is a strong left hand check, the other straight. any experience with this?

there are two crabapple braces (4X6) going up in the frame (tomorrow!!) and i'm a little concerned about them. my buddy (out of whose backyard the tree came) did some reflective carving on a waste chunk remaining and it checked pretty huge. mind you he had left it on his deck in the direct sun, but eventually the wood will get warm and dry out in any case. only the crabapples can really know what it's made of.

From what I've read... Softwoods tend to start with a left spiral which changes to more vertical or right spiral as the tree matures. Hardwoods tend to start with a right and move towards a straight or left spiral.

From what I've worked with... I tend to, seem to, think, I have more trouble with lefties in softwoods. They are rarer, catch my eye and so I probably look at them harder.

What I speculate... in softwood the lefty is often a juvenile with all the troubles that accompany immaturity. Shrinking from duty in any direction possible, not able to hold up their end of a job, rigidly stubborn as all get out.

Restrictions on lefties is being written into log codes that are moving through the ICC in the last draft as I recall. Several authors have claimed a scientific basis for this. Mackie claims lefties are proven to be weaker and inferior. The grading instructor looked at me like I just fell off the truck when I asked there. I have asked if anyone knows of this research to back up what is being written into law. Thus far I haven't seen any. As I said, I'm not sure I disagree, just would like to see some backup.

Whenever lefties and righties come up I think of gums and elms and other interlocked grains. The tree grows righty for awhile, then lefty, then back again. I guess it depends on when you fell it

This piece of old heart pine crossed my path today. Looking at the growth rings I would say "its a straight grained tree". As it checks it shows that the straight appearing cylinders that were being laid down were. But in this case they were also rotating left around the tree. It was a straight tree but mildly twisting left.

Nice photo Don. Had this not have checked already, would you have noticed the spiral grain? One often assumes that the grain (direction of cells) is parallel to the grain (surface appearance or figure.) I have heard the left vs. right bit on the spiral, and still have trouble comprehending why one would be stronger than the other.

I seriously doubt I'd have noticed it in green. Slope of grain, especially what I'd call "local slope of grain" near joinery can be a biggie strengthwise. You know real quick with a drawknife, chisel or slick. Apologies to BB and Eric C, Derek's had the jukebox in my head singing "Riving with the King" all week .

I would like to hear more on the righty lefty thing as anyone comes across it.

"From what I've read... Softwoods tend to start with a left spiral which changes to more vertical or right spiral as the tree matures. Hardwoods tend to start with a right and move towards a straight or left spiral."

Cool topic. I find it interesting how trees grow and timber moves. I wonder too what the reasons are for the spiraling trends. Would the sun changing in the sky through the seasons effect this?

Anyone, are the points where these right to vertical or left to vertical, etc. at a general point on the tree?

Hi Christopher, Don, et al,

I was in a 5 bay barn at Ockley in Surrey yesterday and observed that this 18th century barn had been constructed using nearly all "reused timbers" many of which were of much greater antiquity.

One of the major observations made was how both spiral grain and straight grained timbers had been employed for the main jowl posts in this barn with both left and right hand spiral in evidence on separate post timbers.

Up until this moment I had always considered spiral grain timbers to be bad news but I may just have had a change of heart. Where large spiral grained timbers are left fairly intact by the conversion process e.g. boxed heart with some wane, then the checks developed on these timbers tend to be multiple small surface checks rather than one large check through to the heart as per straight grain timbers.

I noticed that the jowl on a straight grained post had developed a huge long check about 5 feet long down a line from where the teazle tenon meets the tie beam and wall plate. This rather obvious and predictable plane of weakness failing was not repeated on the spiral grain timbers where loads are conducted down the grain, rotating as they go and thus tending to prevent an obvious plane of weakness from developing that coincides with the geometry of the piece concerned.

Critical observations are important as is factual analysis when determining best practice.

Mr Phleps arguments may well hold true for log buildings where a rotating timber might lift and entire wall but this might not necessarily be a relevant concern in a timber frame especially where a timber might be free to rotate - e.g. a main post at a barn door which only has mortice and tenon connections on one side.

Regards

Ken Hume