American board sizing

[condeesteso]

Just so I know... can someone explain the way US workers talk about (for example) : "I made test cuts in a 8/4 air-dried walnut board" for example. What do these fractional-looking board sizes mean?

 

[No skills]

I thought that its simply a measurement in full quarters of an inch eg 8/4 equals 2".

prolly wrong though.

 

[monkeybiter]

http://www.popularwoodworking.com/wp-content/uploads/buy-use-rough-lumber_5F00_start-out-thick1.jpg

HTH

 

[No skills]

Theres a first

 

[monkeybiter]

=D>

 

[condeesteso]

so Skills is right then, it's just quarters. I had assumed it said something about width, i.e. both dimensions. Got it now, but does 8/4 tell me something 2" doesn't?

 

[Droogs]

It lets you know that it's width and not thickness being talked about

 

[monkeybiter]

It's the opposite, according to the Pop Woodworking article

 

[blackrodd]

http://www.popularwoodworking.com/wp-content/uploads/buy-use-rough-lumber_5F00_start-out-thick1.jpg

HTH

Thanks Monkey biter, didn't know that, I do wonder how multiples of 1/4" in thickness came about,
Any one know?
Regards Rodders

 

[No skills]

I think theres an online article about all this somewhere, stuffed if I can remember :lol:

Maybe because a 2x4 isnt really 2x4 (ie undersized) but 4/4 stock will actually be 2" thick.

But again that might be wrong.

 

[JakeS]

Maybe because a 2x4 isnt really 2x4 (ie undersized) but 4/4 stock will actually be 2" thick.

Isn't a 2x4 called as such because the bit of wood that it's planed down from is 2" thick and 4" wide?

Anyway - I'd expect that the "eight quarters" thing is - ironically - just to make sure that there's no confusion! If a timber merchant (sorry, a lumber merchant) is asked to provide two planed boards, "one three-quarters and one two", then there's the potential confusion as to whether the second board is two quarters of an inch or two inches thick. If everyone always talks in quarters, there's no ambiguity. This works in particular because timber merchants are always happy to help newcomers understand all the jargon to avoid confusion. ;-)

 

[Chrispy]

I've nothing to back up my theory but I thought that this is a sawn terminology ie. it stems from the sawmill where the conversion saw would be marked in quarters,
one click per quarter so four clicks to the inch etc.

 

[monkeybiter]

That sounds very plausible.

 

[condeesteso]

I'd like to think Chrispy's is founded in fact, otherwise it all seems a bit of contrary-ness (like there's no 'I' in aluminium, and a router is a sort-of sat-nav)

 

[custard]

I think theres an online article about all this somewhere, stuffed if I can remember :lol:

Maybe because a 2x4 isnt really 2x4 (ie undersized) but 4/4 stock will actually be 2" thick.

But again that might be wrong.

It's not that clear cut. 8/4 (for example) is a measurement of original sawn thickness, the board was originally sawn to eight quarters, or 2", thickness. But if it's been subsequently planed it could be quite a bit thinner.

You see the same thing in this country, a timber yard might have a stack of 50mm sawn boards that are likely to be pretty close to 50mm. But they may well have taken a few of these sawn boards and planed them, before putting them on display as individually priced boards. In which case there's every chance they'll be described as 50mm, when they might be actually 43mm or 38mm or 46mm or some other figure less than 50mm.

It's certainly not a problem; you're a woodworker, you own a tape measure, you measure the actual board, you check against your cutting list, you decide to buy it or not.

 

[RobinBHM]

Ive always thought the term originated from hardwood log conversion. Mostly logs are converted into these thicknesses: 1" 1 1/4" 1/ 1/2" 2" 2 1/2" and 3" and these thicknesses can all be quoted in quarters, ie; 4/4, 5/4, 6/4, 8/4 etc. The board width isnt relevant as conversion is largely through and through resulting in waney edge boards, these may then be square edged, but to a random size based on maximum yield.

In my experience the actual board thickness can vary quite a bit. Hardwoods from North America are usually quite tight on thickness, wheras African timbers are more generous. I dont know if the boards are cut slightly over in thickness to allow for shrinkage in the kiln, or how much that might be.

Square edged hardwood boards are usually rounded up or down for selection and pricing purposes, so if ordering an 8" wide board, the actual board may be 7 1/2" wide or up to 8 1/2" wide.

Softwoods are always sawn to specific sizes, so could 6" × 2", good old 4" x 2" etc. Im not sure if these are quoted as 8/4 etc thick, in the states.

 

[Sgian Dubh]

Ive always thought the term originated from hardwood log conversion. Mostly logs are converted into these thicknesses: 1" 1 1/4" 1/ 1/2" 2" 2 1/2" and 3" and these thicknesses can all be quoted in quarters, ie; 4/4, 5/4, 6/4, 8/4 etc.

I think you're right about the derivation or source of the /4 nomenclature, but I can't verify that.

I dont know if the boards are cut slightly over in thickness to allow for shrinkage in the kiln, or how much that might be.

Sawmills in North America (and elsewhere) generally allow 10% for shrinkage in the kiln. So, for example, a 1" (4/4) dry target thickness is typically sawn at 1-1/8", and 2" (8/4) milled out at 2-1/4". The reason, of course, is most buyers reject wood sold as 1" thick rough sawn if it's thinner, but are more than happy if it's, say, 1-1/128".

Softwoods are always sawn to specific sizes, so could 6" × 2", good old 4" x 2" etc. I'm not sure if these are quoted as 8/4 etc thick, in the states.

Speaking primarily of the US, but also officially metric Canada, but still seemingly using quite a lot of inches and the like in woodwork, the convention for sawn lumber (what we know as timber) of this type is to drop the /4 thickness designation, and to sell the wood described in the order thickness X width X length, the reverse of our convention, e.g., 1" X 4" X 12'. It's quite common to hear an American woodworker say something like "I'll buy a load of 'one by' and '2 by' for this job". Slainte.