So jeff... what is 4/4, 5/4, 6/4 and 8/4?

jeff... · 10-09-2007, 11:58 PM

I've received a couple of emails from folks who are wondering what I mean by 4/4, 5/4, 6/4 and 8/4 in my lumber forsale threads / ads.

There is a straight forward answer but first I would like to speak from experience. Before I got my sawmill I purchased rough sawn lumber for my furniture projects from different folks who run a saw mill like I now do. Some of the sawyer understood when I said 4/4 and some did not. Basically there should be two rulers on a sawmill, a quarter inch scale and a regular inch scale. The quarter inch scale is also called the hardwood scale and the regular inch scale is known as the softwood scale, confusing as this may sound it's really not. When hardwood dries it shrinks more than softwood. So the hardwood scale makes allowances for hardwood shrinkage rates. When you compare the two scales, the regular inch scale reads just like a tape measure would read. However the quarter inch scale adds an extra 1/8 of an inch and is only marked in 1/4"s starting with 4/4.

So the bottom line is lumber cut to the quarter inch (hardwood) scale will always be 1/8 of an inch thicker than lumber cut to the inch (softwood) scale. Hardwood scale 4/4 = 1 1/8" 5/4 = 1 3/8" 6/4 = 1 5/8" 8/4 = 2 1/8". Lumber cut to the inch (softwood) scale will be just as the softwood scale reads 1" = 1", 2" = 2" etc...

The way you would measure a hardwood board cut by the hardwood scale is in 1/4 inches only. So 4/4 would be calculated as 1.0", 5/4 at 1 .25" 6/4 at 1.5" and 8/4 at 2.0 inches. For example consider a piece of oak cut to 4/4 x 6 - 8'. BF (Board Foot) = thickness * width * length (in feet) / 12 so the oak board would be 4BF. if it were cut to 5/4 thick it would be 1.25 * 6 * 8 / 12 = 5BF.

When I saw I don't concern myself much with the width of the lumber, I just try and get the maximum width from each log I cut. If a board measures 6 and 3/4 inches wide I count it as 6". If it were to measure 7 and 1/8" wide I count it as 7". Length don't matter much either, if a board measure 7' 9" long I count it as 7' long if it measures 8' 1" long I count it as 8' long. etc...

One thing I would like to caution folks on is buying hardwood lumber cut by the inch (softwood) scale. Although they may be ok for fence boards, trailer decking and rough construction. Hardwood cut by the softwood scale MIGHT NOT plan to the thickness your expecting for furniture stock. Remember hardwood shrinks more than softwood does when it dries, this is where the extra 1/8 on the hardwood scale becomes important. After drying expect hardwood lumber to dress out 3/8 an inch less than it was originally cut when green (wet). You should expect 4/4 hardwood lumber to dress out at 3/4" thick, 5/4 to 1" thick, 6/4 to 1 1/4" and 8/4 to 1 3/4" thick. Likewise expect softwood like pine to dress out 1/4" less than it was when cut green.

I hope this clears things up a bit and I didn't confuse some of you more than you already are.

I'll try and snap a picture of the two scales so you can see what I mean.

Thanks

nelsone · 10-10-2007, 12:05 AM

Hey Jeff, Great explanation! It took me quite a while to understand some of the sawyer terms and I still have fun calculating BF! This should help a lot of people!

Canuck · 10-10-2007, 12:23 AM

Thanks Jeff for that detailed explanation! I honestly wasn't aware of the two types of measurement - hardwood vs softwood. After reading your post I must say that I am still learning.

Never was any good with math.

The LOML says that she is going to pick me up one of these ..... to help me BF calculations....

http://www.lowes.com/lowes/lkn?actio...525&lpage=none

(I honestly think that she is lookin' for me to cut down on my wood purchases!

)

Thanks again!

Wayne

Kyle · 10-10-2007, 01:18 AM

There is also a big difference between sawing for grade and the 1/4" scale Jeff mentioned. Sawing for grade allows for shrinkage.

jeff... · 10-10-2007, 01:38 AM

Originally Posted by Kyle

There is also a big difference between sawing for grade and the 1/4" scale Jeff mentioned. Sawing for grade allows for shrinkage.

good point Kyle, I just wanted to keep it easy to understand without all the sawyer jargon...

redhawknc1 · 10-10-2007, 08:42 AM

Sure wish we had all this sawyer type info in 1 place to refer to easily! Great information and thanks again!

Robert Arrowood · 10-10-2007, 09:06 PM

Wow! I needed that.Any way that can be put into frequently ask questions? Some of us might need it later. Thanks alot Jeff.

Robert

jeff... · 10-10-2007, 09:58 PM

Exciting as it is, here's a pic of the two scales on my saw mill, notice the softwood scale on the right hand side reads just like a a tape measure. But the hardwood scale on the right is a quarter inch (hardwood) scale. Notice the distance between the 4/4 marks on the hardwood scale is actually a distance of 1 1/4"

. It's that way to allow for an 1/8 blade kerf and an extra 1/8 inch in lumber thickness. Cutting to the inch scale (softwood) will leave you with a board either 1" or 7/8" thick depending how the sawmill is adjusted. I have mine adjusted so when the mill head pointer is on last 4/4 mark (mark closest closest to the bed) it cuts an 1 1/8" thick board.

Thanks

lwhughes149 · 10-10-2007, 10:22 PM

Jeff, thanks so much for this thread. This is probably my third attempt to understand bf. I wrote it in my reference book to go back to. The more I use it the easier it will be to remember it. Also, I also didn't know there were two rules for measuring soft and hardwood. How do we know the width of your boards when you post them for sell? Thanks again. Lorraine

jeff... · 10-10-2007, 10:53 PM

Lorraine, Board Foot is easy to remember once you calculate a few boards it'll come like second nature. Some folks figure it by taking the actual measurements and dividing by 144, I think that's used more for smaller pieces and turning blanks to calculate board inches. For most all of my lumber runs the quarter sawn boards are random width from 4" to 12", I might kick out a couple of 3" wide boards if the grain is good. The flat sawn boards are from 6" to as wide as the logs will yield. Last run we had some 16" wide flat sawn maple boards. I don't really don't understand why folks like wide boards? Don't most jointer's run around 8" capacity? Unless you got a 16" woodguy jointer...

Thanks

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