Shrinkage

[Crossroads]

I ran a bunch of 2x through the edger a few weeks ago and didn't measure any of it to verify that it was coming out at 7 1/4" wide. A couple days ago I was walking by and happened to throw a tape on it. To my surprise it ranges from 7" to 7 1/8". The wood is Doug fir. I'm just now starting to mess around with drying and processing, is a 1/4" of shrinkage to be expected on a 2x8? Next time I set the edger up, I'll definitely be checking what's coming out of it.

[customsawyer]

I've never sawed Fir however that much and maybe a little more shrinkage would be in line with SYP. Might be a little quick but this time of year it can happen.

[scsmith42]

Doug fir shrinks between .0015 (radial) to .0026 (tangential) per inch of width, per percent of moisture reduction.  So for structural use, it will lose around 14%MC  drying from 30% MC to 16% MC.

So a 7.25" wide board will shrink at most 7.25 x (.0015 or .0026) x 16, or between 3/16" to .300" in width as it dries.

So your results sound about right to me.

[bannerd]

What about shrinkage end to end or does that not ever happen?

[Ianab]

What about shrinkage end to end or does that not ever happen?

Usually so small that it doesn't matter. 
There is some slight lengthwise shrinkage in wood as it dries, but it's about 100X less than the cross grain, so we tend to ignore it. 

[Don P]

The exceptions to that are juvenile wood and reaction wood. Those fibers do shrink in length as they dry and are the force at work behind a number of drying warps.

The juvenile wood on the upper face of this board shrinks in length as it dries, bowing the piece. Enough length shrinkage that it sheared 2 deck screws.

[Crossroads]

Thank you, I'm actually pretty surprised that it would shrink that much. One more lesson from the school of hard knocks in the books. Fortunately I have a project at home that I can use it all up. I believe I'll be spending a lot more time on this section of the forum. Thank you again!

[Southside]

The shrink sounds right  - but as you said, you don't know what you were actually set up to cut, so hard to say.  I know on my edger there are two brass wear rods that hold the adjustable blade in place for fine adjustment and weekly I need to bump them in ever so slightly due to the brass doing what is was designed to do.  Only takes a minute if that, but if I don't the adjustable blade would fall out of alignment with the the indicator and my output would not be what I thought it was going to be.  

[bannerd]

What about shrinkage end to end or does that not ever happen?

Usually so small that it doesn't matter.
There is some slight lengthwise shrinkage in wood as it dries, but it's about 100X less than the cross grain, so we tend to ignore it.

Good info here, Thanks!

[Crossroads]

Sounds like I have been putting to much trust in my edger. I plan on swaps the blades out as soon as I get time. That should be an adventure 

[Southside]

Not really - it's a tool and now and then you need to calibrate and maintain it.  Just like the scale on the mill can get off. 

[Magicman]

Just round figures but when sawing framing lumber; on 4 & 6" I oversize 1/8", on 8 & 10" I oversize 1/4", and on 12" I oversize 1/2".   The key word is being consist.

Note that there can be a significant difference between sawing fresh felled and 'old' logs.  You can expect more shrinkage plus stress in fresh felled which is why I prefer to saw 'old' bark slipped SYP logs.

[Crossroads]

All good info, thank you! 

[YellowHammer]

There's enough shrinkage in wood that the Hardwood Market Report (the gold standard for wood prices) has different specs for "green off the mill" and "kiln dried" due to the amount of shrinkage and volume loss. 

[Crossroads]

I ran some 1x through the edger today and they were all 1/16th over, so I'm either looking at shrinkage or I done messed up on my edger settings. I guess 2x8's will be getting an extra 1/4 from now on.