To detect runout in an unfinished top, all you need is a good light source. I use a long fluorescent tube, oriented straight across the grain. Lay the two halves of the top together in the same plane and observe the reflected stripe. If the stripe is straight across, that means the tree has no spiral. If the stripes on the two halves are not offset at the joint, there will be no visible runout in the finished top. Angled stripes mean the top was cut from a spiral tree. Even so, if this angled stripe is not offset at the joint, you will not see runout in the finished tops.

I have photos somewhere here that show all of this, and I have posted them on the forums on numerous occasions. Maybe someone has copied and saved them, since the idiots at Photobucket have chosen to be greedy, instead of doing the right thing.

This is not a result of being off-quarter. In fact, the only way to cut a spiral tree with perfectly vertical grain throughout is to cut parallel to the pith along the length of the log. This introduces runout on the bark edge...the edge that is usually joined when processing small diameter trees.

To cut a bark edge joined top with zero visible runout, the billet is split and sawn parallel to the split at the bark edge. This creates a top that is only perfectly quartered at one location along the length of the top. But because the growth ring radius is greatest on the bark edge, the top will have good quarter at the joint, and will only be off-quarter on the outer corners of the joined top, where IMHO it doesn't matter. While cutting a spiral billet, the point along the length where the cut intersects the pith (perfect quarter) is entirely under the control of a skilled sawyer. If you place this in the lower bout, the top will have perfect quarter at the bridge, all the way to the outer edge of the top.

The amount of runout on the outer edge of the subject top is IMHO a nonissue if there is no runout at the joined edge. That is because the top needs to be strongest in the center where the bridge is glued on.

I agree, but I wish there was a way to know.

http://www.lutherie.net/frankford.runout.html

Toward the end of the article Frank mentions that "off quarter" can also create that effect.

P.S. My prices are considerably less than Kevin's, so what I let out of my shop may be different than what he should let out of his.

Bryan I think what he means is when you cut the top off the log that is not perfectly on quarter on the outside. Near the pith the grain lines are up and down but as you get closer to the bark they go off. So one half would look like this |||||/////

The jointed top would look like this: ///////||||| ||||||//////

The first few cuts off a perfectly quartered log will be perfectly straight grained but as the bark edge rounds off you start to get slanted lines.

A bookmatch where one side is flipped could give you the grain match Frank mentions. Why would someone do that? Ask the guy gluing up hundreds of tops a day.

It seems like some people's clients are getting hung up about the look more than what the guitar sounds like. At one time runout was not a consideration when buying an instrument. Even a good quality top can show some runout under finish. As builders we all have to choose where we draw the line. It looks like the wood cutters are going to have one more semi-cosmetic criterion for grading their tops.

I'm really not a fan of nosed tops. Hard to keep deflection data consistent.