How to determine runout in spruce top billets

[kiwigeo]

Thank you mate.

LOL....weve got you talking like a dinky die Aussie already

[charangohabsburg]

Thank you mate.

LOL....weve got you talking like a dinky die Aussie already

That's called mental runout.

[charangohabsburg]

I hope that I will nail down also that silk thing in a decent manner. Just give me some more days.

Finally. Here.

And oh, yes. Instead of splitting the wood you can also look at runout by using a $5 hand lens with adequate lighting. For example one like I showed here.

[mqbernardo]

Hi all! New to this forum, but i feel like i already know some of the regulars from "other" forums. I´m really enjoying the tutorial section here, thanks all for the work.

Now, regarding this topic, Markus would you be so kind as to let me know how you calculate the runnout ratios? thanks a lot for your work. It´s much appreciated.

cheers,
miguel.

[charangohabsburg]

Hi Miguel, welcome to the foreigners club of the ANZLF

If you look at the second picture of my first post you can see a long "horizontal" pencil line, a short "vertical" pencil line and the diagonal split line (the latter indicates the fiber orientation, thus the runout angle). Measuring the two pencil lines gives you the two numbers that define what I call "runout ratio". Not much math included.

Cheers,

[mqbernardo]

thanks for the welcoming, Markus. This place seems a friendly one.
I didn´t notice the pencil lines, that makes it clearer.

again, thanks for such an informative thread.

cheers,
miguel.

[charangohabsburg]

Inspired by some confused people on one of the other luthier forums I decided to write down a little update on how to detect runout making good use of some very cheap, respectively "still cheap" toys.

The spruce sample pictured in this post is exactly the same you can see earlier in this thread (on the first page, here and later).

As I mentioned here a couple of posts ago, if one doesn't want, or is not allowed to split the edge of a Master- or whatever- grade top it is easy to detect runout with an inexpensive hand lens:



There exist quality hand lens of the type I labelled with 2), but the one pictured here is a cheap one (in the 2 $ range), and although it is enough to see runout I would not consider it being worth the 2-3$ because only the centre of the centre of the picture is sharp, the magnification on the lower side, sufficient lighting is difficult and keeping the distance (e.g. sharpness) steady is not so easy either.

The lens labelled 3) is the one I mentioned in a former post, costs about 3-5$ and comes with a built in LED which is handy when using it at night, but not necessary at all when bright sunlight is available. The magnification of this "curreny detecting microscope" is about 60x, or at least this is what they call it. The "microscope" can be plunged right down on the specimen and then you adjust the sharpness with the telescopic tube. It is really easy to use.



1a) shows the splitted surface as it can be seen earlier in this thread, but it is not very well suited to look at it with a magnifying glass.

1b) shows the surface smoothed out with a knife (or chisel if you like). Smoothing with sandpaper is less desirable because when looking at a relatively "rough" wood surface it can be hard to see details such as the running direction of the wood cells (tracheids).

For taking photographs of runout (or other microscopic wood features, the minimal equipment is a USB microscope (ca. 30 - 80 $, maybe there are now even cheaper ones in the 15$ range or so). Of course one can not expect miracles of these things, but hay, at least you can take a picture that shows runout without having to split the "high grade" top before you are going to return it to the provider! (Geez, some luthierie-spruce providers will hate me for what I'm writing here! )

Well, this is one of these cheap USB microscopes...


...with which I took this picture of the 1a)-part (raw split) of the specimen above...


...and this picture of the 1b)-part (carved surface):


Note the sharper picture the carved surface delivers. This has also (but not only) to do with the not so great depth of field of any magnifying lens system.

With the hand lens 3) you will see a sharper picture than you can take with a cheap USB microscope.

That's all for today folks. I hope you enjoyed it, or at least found it useful.

Cheers,