J
jeff...
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
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
