American Timber Sizes

[KeithP]

Could anyone give a quick explanation of how American timber sizes work. In magazines I read sizes like 8/4 and 4/4 etc. and are wondering how that relates to our timber sizing.

Regards
Keith

[rob streeper]

It's a mess. 4/4 generally, but not always, means four fourths of an inch, i.e. one inch with a tolerance of +/- 1/8". Some 4/4 is closer to 5/4. Dimensioned lumber is smaller than it's stated dimensions. For instance a two by four is actually 1.5" X 3.5" with a tolerance that varies from 1/16" to 1/8". A rough sawn two by four is 2" X 4" +/- some. Sheet stock is generally true to measurement.

[John.G]

What Rob said. Thickness is measured in increments of 1/4 inch, so 4/4 is inch, 6/4 is 1 1/2" etc.

in practice most is over sawn considerably, they don't tend to use line bars and hob feeds so much, and there's a lot of thin band equipment with resultant hit and miss and blade wander...thickeness accuracy isn't that great compared to here. So as a result they'll commonly saw 1/8 to 1/4 oversize to allow or that.

US finished sizes are nominal: here we'd sell a 6x2 as 150x50 and if it was DAR it would be sold as 140x42. There it's just 6x2 rough or 6x2 DAR and everyone understands that means it was 6x2 before it got dressed. There's very little GOS timber used there also... nearly all KD.

The US timber market is a lot more sawmill friendly then here in terms of consumer expectation overall.

[QC Inspector]

The quarters are the measurement when the board is cut from the log when it is green and not seasoned. So 4/4 is 1 inch thick, 6/4 is 1 ½" thick, 8/4 is 2" thick and so on. When the wood dries it will be a bit thinner. The wood normally sold this way is normally for furniture.

Lumber for construction is sold dried and planed. Thus the 2x4 is the rough lumber size and after being dried and planed is 1 ½" x 3 ½". 2x6 will be 1 ½" x 5 ½" and so on.

It's all what you learn to use. When you gents talk about cubic metre prices for hardwood, I'm lost. But price per board foot I can relate.

Pete

Sent from my iPhone.

[KeithP]

Thank you gentlemen, now I have some understanding.
I'm glad I work with the system we have here in Australia.

Regards
Keith