How accurate/precise is your "rough" lumber?

[Redhorseshoe]

Just wondering what you all would consider as acceptable for lumber consistency right off the mill.  Say you cut a 1 x 12, 8 feet long, do you expect that board to be EXACTLY those dimensions the entire length of the board?  Or is a very slight variance acceptable?  Example, I just milled about 20 2x4's which all came out just right but then (from the same log) I also milled around 45, 3/4 x 5 3/4 boards and  some of them have around 1/8" variance in width.  Not every board mind you, but some are right on the money most of the board but will narrow to 5 5/8" somewhere in the middle then come back to 5 3/4".  My guess is there was a knot or something that caused a little deflection in the blade when I was sawing the cant and that caused the irregularities.  Or am I just overthinking this?

[ladylake]

 
 If it's not stress in the log causing it you need a little more pressure on your center jacks or supports.  Steve 

[longtime lurker]

I usually sit on +2mm sizing to account for any wander, and rarely get that much (circle saws).

If they are all consistently scant in one area  in the middle I think it's most likely stress bowing your cant/log up during sawing

[customsawyer]

It could be stress in the log where the middle rose up a little as you were sawing the sides or you could have had a small piece of bark under your cant. Also your blade could have pulled down a little due to grain in the log or something.

[Ianab]

"Rough Sawn" is seldom perfect. Logs and cants can warp as you saw them, blades wander around knots etc. And then wood shrinks by different % depending on species and grain orientation. So sawing green wood to more than 1mm (1/25") accuracy is basically pointless. the 100mm board green board could shrink by 3 to 10 mm as it dries, depending on "things". 

The specs on the Peterson mills say they are accurate to +/- 2 mm, which lines up with Meadows +2 mm rule of thumb. If everything is running sweet, then you might only get +/- 1 mm , but if you allow for 2, then you don't have the rejects. Some might be 1 mm over, and some 3 mm, but they are in spec. 

But ideally you do want to minimise the variation, and work out WHY you are getting it. If you are getting boards thin in the middle then squat down and eye down the bottom of the cant. Has it warped as you take boards off one side? Then it's the wood, not the mill. Time to start flipping the cant over and taking couple of boards from each side to even out the stress. Takes more time, but you produce a more accurate product. 

Large knots and weird grain are usually visible, so you can put variations down to that, and just deal with it

Other times it's the mill (or mostly the blade) causing waves, and something needs sharpening / fixing. 

[cutterboy]

Rough lumber is just that "rough". With hardwood the furniture maker is going to plane it, recut it, and sand it so a tiny bit of variance in the board is ok. With softwood that is going to be used just as is, in fencing, siding, roofing, etc., then again, a little bit of variance is fine.
I wouldn't worry about it too much. Good luck with your sawing.

[moodnacreek]

If the turn boards and last boards are usable/sellable  I'm doing fine.  When boards don't saw out good you need to at least know why to be a good sawyer.

[richhiway]

Nice to get perfect dimensions but it is called rough cut for a reason. It all depends what is acceptable to the customer/use of the lumber. 
Anything less then 1/4 should be O.K. in most cases. 
I know that when someone needs say a perfect 8x8 for a timber frame, it will be cut over dimension, have time to dry then is cut to size.

Nice logs make nice lumber. This is why big mills pay for grade. 

[Beavertooth]

My lumber is so accurate that NASA uses it to gauge all of their instruments by.   8) 8)

[WV Sawmiller]

   Is that why the shuttle landed in the Gulf of Mexico last week when they were aiming for the Pacific? :D :D :D :D

[alan gage]

I'm sawing mostly hardwoods so I don't worry too much about variation in width since I'm assuming they'll all need to be edged after they dry anyway.

I try to be as consistent as I can when it comes to thickness and hate thick/thin spots. This past year I've been planing a lot of lumber and much of it is lumber that I bought at auction rather than milled myself. Much of this has high spots in the middle of boards and lots of boards varying from 1" to 1 1/4" in the same stack. This is a real PITA when planing because the most my planer can take off is 1/8", which means if I hit a high spot the planer chokes and stalls and then I need to drop the bed, pull the board back, and take a couple shallower cuts until I'm back to the same thickness as the rest of the boards. Usually, because of these high spots, I take a 1/16" cut instead of 1/8" to keep it from stalling so much. Of course then it takes more passes to clean up...

I'm happy to say that my lumber has been much more consistent which makes planing much faster and less aggravating.

Alan

[scsmith42]

We try to keep accuracy within 1/16".

Thursday we spent a good portion of the day making flooring from customer supplied blanks.  He brought us a few thousand board feet of red oak 4/4 x 6 for kiln drying and processing into flooring.  I don't recall if he milled them himself or had it done locally..... but

Thicknesses varied by 1/4", and were to the point where we had to presize every blank though the jointer/planer so that we weren't hogging a bunch off of one face in the moulder.  It was a bit of a pain and added several hours to the job.

[WDH]

planer chokes and stalls

If that happens a lot you get to buy a new motor.  Don't ask me how I know this... . 

[Patrick NC]

I'm new at this, but I'm pretty happy if it's within 1/8". I made a lot of not so pretty boards before I figured out to change blades before they are dull and not to push too fast. I've still got a long way to go, but the guy that buys most of the cedar I cut is really happy with it. 

[farmfromkansas]

I am thinking of calling Cooks and ordering a table with the thicker marks.  My saw makes 4/4 about 1/16 thinner than I would like.  Once in a while I get a board that will not clean up at 13/16", or 7/8" which is better.  Those I run down to 11/16 to use as a raised panel, or drawer sides. I like my glue up panels at least at 13/16, so they will sand out to 3/4" finished. If I use 7/8" frames on panel doors, and a 11/16" panel, I can sand down the face flush with the wide belt sander. Don't really want to cut at 5/4 to make a 3/4" board.