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Numbers divided by a slash? 4/4, 5/4 etc...1/23
Yeauh i know... I'm showin' my ignorance, but it's worth it to get the answer. Then that's one less thing I'll be ignorant about.
There are four quarters per inch.
OK, so board thickness in fractions of an inch; gotcha. Thank you Josh.
Let me add a bit more to the discussion.
For hardwood lumber, 4/4 means that the thickness when green or air-dried is between 1.00 and 1.24" in the area of the lumber that is used to establish the grade. Then 5/4 is 1.25 to 1.49"; 6/4 1.50 to 1.74"; etc. Now, if the lumber is kiln dried, a 5/4 piece that was 1.27" green could now be 1.22" due to normal shrinkage. So, the rules do allow for this shrinkage by defining the KD thickness of various thicknesses differently than green or air-dried. For example, 4/4 through 7/4 can be 1/16" thinner than the minimum for green. And 8/4 and thicker can be 1/8" thinner.
For softwoods, the nominal size and actual size are far apart. For example, the nominal size might be 8/4, but the actual size after surfacing will be 1.5".
Let me just add that when you say 4/4 (1") that's in the rough. Typically at a hardwood supplier you're going to see planed on both faces, 4/4 will then measure 13/16".
A set of standards for measurements, and grading rules are maintained by the National Hardwood Lumber Association, and most folks working in Lumber tend to follow these rules. This is where the measurements you refer to are defined and maintained.
You can order a copy of the NHLA look at the rulebook here:
You can also order a hardcopy at the main site.
Well... looks like I 'got me some learnin' to do' (that's hillbilly for 'I need to hit the books') and I thank each of you for sharing your knowledge; and I will go to that NHLA web site Eric. Thanks again fellas.
There is no way to order the rule book at http://www.nhla.com/rulesbook#sthash.1zdqzqYK.dpuf.
Actually Bruce, I was able to print the whole book from the website. Thanks Eric.