How much thickness is lost during flattening? The answer is: it depends on the slab. Thickness loss is caused by the removal of defects that dictate how flat the slab is, such as bow, cup, twist, taper, and planer snipe. The depth of these defects varies from slab to slab, but it is easy to figure out how much thickness loss they can cause!
Calculating How Much Thickness is Lost During Flattening
All you need to know is the starting thickness of the slab, the deepest listed depth of any bow/cup/twist/tapers/planer snipe for each side of the slab, and this equation: Thickness – Tapers – Planer Snipe – (Deepest of the Bow/Cup/Twist x 2) = Estimated Final Thickness. You can find all of this on the Product Page below the product images!
Here are a couple things to keep in mind:
Bow/Cup/Twist affect BOTH sides of the slab, so you’ll have to take this measurement x 2.
You only need to know the deepest defect measurement for each side, so if there is a 1/16″ planer snipe but the slab has an 1/8″ bow, you don’t need to subtract 1/16″ from the thickness because this will already be removed when taking out the bow.
Now let’s go over an actual product! Look over the highlighted information below from one of our listings:
This is a pretty easy one to start with! The slab is listed with Tapers up to 1/16″ deep on both sides, Bow/Cup/Twist all up to 1/16″ deep, and 1/8″ deep planer snipe. The Bow/Cup/Twist/Taper will cause 1/16″ to be removed per side on this one, and the planer snipe will cause 1/8″ to be removed from the side it is on. This means that 1/8″ will come off one side and 1/16″ will come off the other side, totaling up to a 3/16″ estimated thickness loss. Fill that into the equation, 2 1/4″ (Thickness) – 1/8″ (Planer Snipe) – 1/16″ (Bow/Cup/Twist/Taper), and you get 2 1/16″ estimated final thickness.
How Do You Know That This Will Be the Final Thickness?
You’ll see we say “estimated” a lot in this article, and that’s because this figure is only a very close estimate and is not 100%. While these defects were at these depths when we listed the product, there is always a chance the wood will continue to move as it’s in the warehouse. The Bow/Cup/Twist may get worse or it could even get better. Our team inspects each slab when they’re pulled from the warehouse and will reach out to you prior to shipping if any of these defects worsen by over 1/8″.
Still have questions? Don’t hesitate to reach out to our team of wood experts – we are happy to do the math for you!
To Wrap it All Up...
You should have a better idea at how much thickness is taken off when flattening a piece. We list as much information as possible on each of our slabs so you'll always know what to expect. When ordering a slab, we will always reach out if we believe the tapers in a slab are deeper than originally anticipated.
Still have questions? Don’t hesitate to reach out to our team of wood experts – we are happy to do the math for you!