Sawing dimension lumber oversized?

[Gilman]

Sorry group, haven't had time to post lately, but I have a quick question for you.

I'll be sawing some dimension lumber for a customer this weekend out of douglas fir.  Should I saw the lumber oversized to allow for shrinking, or saw it right on the 1 1/2" mark?  Also, are there scales for shrinkage?

Thanks in advance,

You're Delinquent FF poster

[Tom]

Gilman,
If you are cutting the lumber to be dressed, then you can use the true scale on a bandsaw mill to make the "2 x" stuff scant.  It can still be dressed to required sizes.

If you are sawing "dressed" sizes for your customer, don't put the measure directly on the 1 1/2 mark.  You will end up with the kerf being taken out of the board and the result will be a "2 x" that is less than 1 12" thick.

You can use the 1 3/4 which will get you closer to 1 5/8's  That should take care of shrinkage and minor miscuts.  Shrinkage will vary depending on grain orientation. That's why they use planers after-the-fact to dress wood.  Don't forget that you are running a sawmill, not a planer mill.

If your customer is wanting dressed sizes, he may also want dressed widths.  You best be assured of what he is expecting before you start.

I am reluctant to cut 'dressed" sizes without the customer understanding the variables. You must also make sure that you both know how the job will be charged.  Are you working by the hour?  Are you charging for board footage based on a dressed size being nominal and treated as a "2 x"?  Is the customer expecting your "2 x" to be charged as a 6/4?

You just need to make sure everybody is on the same page.

[Brucer]

Hi, Gilman

Lee Valley Tools sells a nice little "wood movement reference guide" that'll give you shrinkage information. Their data is taken from the "Wood Handbook" published by the US Department of Agriculture, so that's another source.

For Douglas-Fir, the radial shrinkage is 0.0015 per 1% change in moisture content. In the tangential direction it's 0.0026 per 1% change. Figure on about 20% change in moisture content from green to air dry in your area and that works out to 20 x 0.0015 x 1-1/2" = 0.045" shrinkage in the radial direction and 0.078 in the tangential direction. 'Course there's lots of variation in wood and weather so these numbers are rough guides only.

When I'm cutting wood to size for myself, I just average them and round to the nearest 1/16". For dressed widths you may want to use the higher number, as you could see 1/8" or more difference between lumber from the outside of a cant and lumber from the middle.

Bruce

[Bibbyman]

Welcome to the Fourm Brucer,  Thanks for the tip. ;)

[Gilman]

Thanks,
I'll talk to the customer and offer to cut @ 1 1/2" or 1 9/16"

I knew I'd get a good answer(s) here

[D._Frederick]

Gilman,

For fir dimensional lumber that I am going to use, I saw it 1 5/8 minus the kurf . For the width, I add 5/8. For 2x4 and 2x6, they will dry to 1 1/2 X 3 1/2  and 1 1/2 X 5 1/2 and be close enough to store bought lumber that you won't have any problem.

[Oregon_Sawyer]

Gilman:

You really have to find out what the customer is going to use it for.

I have had customers want their 2x6 fir anywhere from 1 1/2 to 2in.  You will probably end up cutting alot of lumber for pole barns.  Find out if they are going to use hangers or not.  If they are then follow D_Frederick's advice.

The last barn job I cut we cut the joists at 1 3/4 x 11 3/4.  Last week he had me come back a cut studs and he wanted them to fit hangers if needed.  So they were cut 1 5/8 x 5 5/8..

I seldom cut at the nominal size.  I had one job that the gentleman had me cut the studs 1  1/2 x 6.

I charge as if it is a full 2x6.  That is standard around where we are.

Loren

[Gilman]

Thanks Loren and D.
Frederick, do you charge the same as Loren?  2 x 6 for 1 1/2" x 5 1/2"?

I don't think I'm going to get to start tomorrow, Saturday, due to the freezing rain we are supposed to get tonight and tomorrow.  Something about pulling a orange mill that weighs as much as my truck up and down icy hills doesn't sound that exciting.  Hmm, actually it would probably be really exciting.

[Frank_Pender]

Gilman, I charge the same for special cuts as I do for standard dimensional lumber.  If the majority of the lumber is 1' type of msaterial I charge 20% more.  

  Good council on asking the customer what they prefer.  I have done it both ways.  For all of the houses I have sawed, I cut to the standard dimension.   Most dimensional lumber purchased in our region will shrink some as well, with my experience

[Slabs]

Sawing custom lumber sizes consistently isn't all that difficult if you make your own scale stick to replace the one Miser provides.  Select the wet dimensions you want, add the kerf width and mark the back side of an aluminum yardstick in even increments of the thickness or width + kerf.  You can even do the same on one scale for setting up the basic cant.  Use fine tip markers and coat it lightly with clear Krylon.  Look at the original mill scale to see where to start the scale.  The scale clamp will snug on up for the thinner yardstick but you may have to cut a notch or two on the edge of the stick for the clamp screw since the stick is a little wider than the original scale.  I've even used narrow pieces of paneling or edge rips but the paneling will almost dissolve in humid weather.

Slabs