4 ms·
To elaborate a little more: Board thicknesses are measured in the "quarter system" - 4/4 (pronounced "4 quarter", that is 4 quarters of an inch) is a 1" thick
by angry_moose 3y ago
To elaborate a little more:
Board thicknesses are measured in the "quarter system" - 4/4 (pronounced "4 quarter", that is 4 quarters of an inch) is a 1" thick rough-rough sawn board; 8/4 (8 quarter) is a 2" thick rough board.
As this is rough sawn (super rough and unsightly finish), you usually lose at least 1/8" while finishing the board, so a 4/4 rough board gives you something around 3/4" finished product.
This leads to 5/4 being another fairly common dimension, as you can get a 1" finished board out of it. 6/4 and 12/4 are somewhat common as well.
It might seem like an "ugly dimension" compared to something like m^3, but its really built around speed. Watching someone skilled price out an enormous stack of mismatched lumber (width, thickness, and length) in seconds with a lumber rule is always a fascinating process to watch (https://www.popularwoodworking.com/techniques/the-lumber-rule/ https://www.popularwoodworking.com/techniques/the-lumber-rul...).
Usually the $/board foot increases slightly at higher dimensions as thicker lumber is harder to produce. I got some 4/4 black walnut for $12.80/bdft last week; 8/4 was closer to $16.
Edit:
This is also why 2x4s are actually 1.5"x3.5" - historically they were 2x4 rough sawn lumber, but .5" is lost in both dimension when producing finished boards you purchase in the store.
- anarazel 3y agoIsn't the loss for dimensional lumber more due to drying than finishing?
- angry_moose 3y agoThat is some of it and it varies a lot based on the species, though I'm a lot less knowledgeable there. In the hardwoods I usually work with (walnut/maple/padauk) its fairly minimal. A nominally 4/4 board usually comes in about 1/16" small; which is a lot less than I lose running it through the planar. Some of that could be the sawmill skimping out too and cutting just a bit undersized.... I'm finding quoted numbers between 2-8% volumetric shrinkage (https://www.wood-database.com/wood-articles/dimensional-shrinkage/ https://www.wood-database.com/wood-articles/dimensional-shri...), which is still quite a bit less than you find in the small dimension of a 2x4 (2"-> 1.5%, or ~33%)
- PaulDavisThe1st 3y agohttps://www.youtube.com/watch?v=WaJFudED5FQ https://www.youtube.com/watch?v=WaJFudED5FQ
- coryrc 3y agoNo, and they rough cut fast closer to 6/4 (1.5") than the original 8/4 (2") they may have originally used, because we don't care about the quality as much. Part of that is the wood isn't as good. Part is our machinery is now more precise. To get a 1" finished board you need to start with at least 5/4, because you may have some twist in the board and you can flatten alternating sides to make it flat. If you were just running it through a machine without paying attention, your might need to take that same board down to 0.75" to get it flat. But they aren't wasting time like that for framing lumber. But when your lumber is expensive, it's worth a little focused labored to use more of the board
- bluGill 3y agoHistorically 2x4 never had a standard and different sawmills produced different sizes. I've seen houses built in 1880 where a modern 2x4 fit perfectly, meanwhile a different house built in 1968 had a obvious size difference.
- oblio 3y ago> It might seem like an "ugly dimension" compared to something like m^3, but its really built around speed. Watching someone skilled price out an enormous stack of mismatched lumber (width, thickness, and length) in seconds with a lumber rule is always a fascinating process to watch (https://www.popularwoodworking.com/techniques/the-lumber-rul https://www.popularwoodworking.com/techniques/the-lumber-rul...). I imagine there are people all over the world doing the same tricks with metric measurements.