A Stack Of Nominal Dimensioned Lumber
Source: Repair Materials
How is Lumber Sized and Why Do I Need To Know This:
The reason you should know this is because as you are gathering wood for say a clamp-making project, you want to end up with clamps that are X thick and not 75% of the X thickness. So lets review how wood is sized and why it should make a difference to you – the guitar repairman.
Nominal Sized Lumber:
When you buy lumber at a lumber yard or a specialty wood store, you will be talking about (2) different sizes of wood. One of these sizes is defined as Nominal Size wood. You may even see the wood that is finished listed as 2″ x 8″ x 12′ Nominal, when actually it is less than that.
The wood is called Nominal because it was cut out at the saw mill for a log at say that 2″ x 8″ x 12′ size and that is what it actually measured after the cutting.
Actual Sized Lumber:
This is lumber that is fully dressed and dried. In other words it is air dried or kiln dried to a specific moisture content and then run through surface planers and sometime edge joiners to true-up and finish all four sides of the wood. This is also called S2S for the surface planing or S4S for surface planing and edge jointing.
This procedure takes off a certain amount of wood in the process. The amount can vary depending of the wood species and the hardness of the wood. It will usually be 1/8″ planed off each surface. So that piece of wood listed as 2″ x 8″ x 12′ Nominal will actually be 1-3/4″ x 7 3/4″ x 12′-0″ or even less!
What’s With All The 4′s?
You will also see wood listed as 4/4, 5/4, 6/4 or 8/4. You say this like “four-quarter” or “six-quarter”. What it is, is lumberyard lingo for four-one quarters of an inch or 1 inch. Or eight one-quarters of an inch. This again is in Nominal Dimensions.
So if you want to wind up with a piece of wood that is say 7/8″ thick, you will want to order 5/4 or five-quarter, which is 1-1/4″ Nominal thickness and is dressed down to approximately 7/8″ to 1″ thick.
Board Feet:
You purchase your lumber by the term Board Feet. One board foot would be a 1″ x 1″ x 12″ piece of wood Nominal, or 144 square inches.
It can be any dimension, say 3″ x 48″ x 1″. That would also be one board foot. Let’s say you have a piece of wood that is 16″ wide x 1-1/2″ thick and 60″ long?
Just multiply all the numbers together and divide the result by 144 and that is number of board feet you will be purchasing. Just keep your Nominal and Actual dimensions straight.
Lumber Grading – Firsts and Seconds (FAS):
The best and most expensive grade is FAS. Boards are 6″ and wider, 8′ and longer. FAS lumber yields 83-1/3 percent of clear face cuttings with minimum sizes of 4″ x 5′, or 3″ x 7′. FAS hardwood lumber is best suited for fine furniture, cabinetry and applications where clear, wide boards are needed.
Tags: guitar repair wood, lumber sizing and grading, nominal lumber, wood for guitars
