Quarter Sawn Oak

[Hank]

<font color="purple"> 4/4 = 1 inch
5/4 = 1 1/4 inch
8/4 = 2 inch </font>

Right, and when a mill buys hardwoods, they are that actual thickness in the rough, to allow for later surfacing. Mill stock in softwoods is generally sold surfaced on two sides, random widths.

Each thickness also corresponds to various traditional millwork products:

4/4 for cabinet doors, 5/4 for screens, screen doors, storm sash, stair treads, one-sided blinds and shutters, 6/4 for sash, two-sided blinds and shutters, interior doors, 8/4 for exterior doors, to name some.

 

[woodmills1]

actually it is a little more complicated than 4/4 = 1 inch. In the cutting of hardwood a 4/4 board is meant to be a rough stock for what will eventually dried and finished to a one inch board for sale. Now that one inch board, as you probably know, is really 3/4 inch when purchased. The 4/4 rough board has to be thick enough so that loss due to shrinkage and planing leaves it at 3/4. If all was perfect that would be accomplished with a rough thickness of one inch, but given tha marks made by the sawblade teeth and variations due to the saw wandering that may not be so. Most of the rough hardwood lumber is actually 4/4 plus a sixteenth or even an eighth.

I cut with a woodmizer lt40 and it has a dual scale for setting the thickness. One is in inches and the other is called a quarter scale that gives a cut 4/4 board at 4/4 plus 1/16. Lumber that I cut on the quarter scale will plane to the required thickness on over 90% of the pieces. If i use the inch scale the boards come out at somewhere near 7/8" given that the blade is .045" with around .060" of set. lumber cut this way may or may not plane to the desired thickness.