Lumber Accuracy and Consistency

[rooster 58]

     Well yesterday was the first time that I got to work with lumber that came off of my mill. Last Friday I had to saw a small order for a guy who needed the material for a porch on his cabin. Soooo, I fired up the 'Mizer and got 'er done.
    The fellow, whom I know, came by Monday afternoon and payed me for the material. Turned out he needed an extra hand, so I offered my services.
      This material was hemlock, sawed into 3x10 and 3x8, 14 and 16' long.
   Although I had done periodic checks on what I sawed, I did'nt check every piece. Yesterday, I put the tape to every piece of lumber that we had. The worst piece was out 3/32" out from end to end in width. Alot of it was on the money and average runout was 1/16".
      I've used alot of "rough sawn" material in my carpenter days from various mills, all of which were circle mills. We did have one mill that sawed 2x8 oak for horse barns that did a fine job. However, the lumber I sawed was more accurate and consistent than anything I've used, with that lone mill being the exception.
     I even compared my lumber to a couple of 2x8's that were regular dimension stock. Each one of those were out 1/16" from end to end.
    I was wondering if I can actually do better than that? Can I even produce material that is a little more true than what I'm making now? I should say that I am sawing on site on top of a hill with a fairly level spot. But I'm not set up on a hard surface like concrete which might aid in more accurate lumber. Any thoughts or ideas would be welcome. Thanks guys ;)     Scott

[hackberry jake]

With 14' and 16' logs, I dont think any sawmill would do better than that. The slightest tension in the log will make it bow once the boards are removed. The stationary sawmills that cost hundreds of thousands of dollars still surface all four sides of the lumber to maintain consistency.

[POSTON WIDEHEAD]

If your mill got it any closer. we wouldn't need planers or table saws.
There are many steps to get a board perfect......the mill is just the first.

[drobertson]

I agree with jake, the longer stuff will bow up, sounds like you nailed it.  It is nice to work with consistent lumber.

[rooster 58]

Thanks guys for the replies. I sort of thought that would be as good as I could get, but I didn't want to take anything for granted

[NMFP]

The only other way to make your lumber any more exact would be to have additional dogs on the mill to hold the log or cant from moving, other than just the one in the middle like WM uses.  Your within 1/16"..... Don't fix what's not broken.  Too bad all guys running portables didn't worry about it....  This is a reason that a lot of concentration yards here in PA don't like to buy lumber coming from portables as the set thickness and taper is so far out of whack.

Your doing good.... stick with what your doing and it will pay off!

[Brucer]

The first principle of working with wood: Wood Moves.

When I first open up a log, I turn it frequently so I don't take too much off one side (which will cause it to bow up in the centre). Once I have a squared-up cant I clamp it as tight as I can. Then I saw right down from the top without releasing the clamp. Usually I end up within 1/32" from end to end. Sometimes the log moves in an unexpected direction and I'm closer to 1/16.

I see the most "error" on the 14 - 18 foot logs. Shorter than that and there isn't enough bending stress to move the log very far. Longer than that and the weight of the log tends to hold it flat.

Most of my customers are happy as anything to get a rough-sawn timber within 1/16". I send the ones that aren't happy to my competition :D.

[WDH]

The store bought stuff is not any better than that.

[Banjo picker]

I have a very old boise crane planner... want to know how good you are sawing as to thickness.. run some through it. It will tell on you real quick. Banjo

[dboyt]

How the mill is supported can have an effect.  Even with a good, stiff frame, if one of the supports sinks into the mud, it will throw things off.  My #1 issue is with blades, though now that I sharpen them myself, I've gotten more consistent.

[Alligator]

Only one thing will cut lumber more consistent. A sash gang, the lumber will not vary 1/64 per piece on 1" or 2". A stack of 10 will not vary 1/16. I have measured 100s of times. It was one of our main QC checks. Pipe clamp 10 boards and measure. That was suppose to be 9 3/8". Rarely was it out 1/16.

On a mill where you move the saw or the log 3/32 is great accuracy. On our headrig 1/4 was the norm, but we tried to only make cants. I found an interesting sash gang, small compact, as sash gangs go. https://www.youtube.com/watch?v=pBjTdtQR90g It is Ukrainian. Pretty fast 2:30 on 8 saw lines thru a 6" or ever how many mickmeters that is :D.

[backwoods sawyer]

Consistency day in day out saw change after saw change comes from proper alignment, when you notice something out of whack, track it down and fix it.


Production mill have multiple machine centers that are continually monitored with a pair of calipers with a storage unit attached that measurements are then down loaded into the computer and a spread sheet is generated, depending on species  the target size varies cedar 1.500 and .750 doug fir/hem fir 1.570 and .870 spruce 1.650 and  .940 If the measurements were more than .015 off saws and guides were changed this allowed for skip planning by the rule book.

To measure the 4" and 6" thin kerf edger's I would pull two boards from each pocket, then measure at four locations down the board flip the board and take four measurements up the bottom this gives an accurate picture of each board.

You can do the same thing with the mill just slice a stack and take a few measurements verify how consistent the wood is coming off your mill, use the long jaw calipers as they are less likely to rock on fibrous wood.  I keep a pair within reach when running the mill. My tollerance is .015 as well and you will find veriances from time to time just correct them when they are found.
Tape measure is best used for length ;)

[delvis]

It's called rough cut for a reason and with logs that have any sweep in them AT ALL, you're going to get some variance in the thickness of the boards, especially the bottom two boards.

The large lumber mills have multiple clamps they can force the cants flat with and they re-saw everything to the thickness they want anyway.

[giant splinter]

1/32nd // 1/16th is perfect for most projects, so many factors will throw things off and the longer the log the more likely you will see the deviation. I have always thought that alignment and a fresh band is a good way to get a clean and uniform board, after having a circle mill and switching to a band mill I still think the old circle mills where a great design and wished I had kept that old sawdust slinging monster when it comes to sawing larger beams as those 54" blades would cut straight as an arrow and got right down to it with large logs. When it comes to accuracy and consistency I always liked the circle mills performance, on the other side of that I DO-NOT miss the sawdust mountain or the fuel bill. ;D

[dboyt]

I made a metal go-no go gauge for the Sawmill Shoot-Out to determine whether boards were within tolerance for 4/4 & 8/4 boards.  Anyone who questioned it was welcome to check the gauge with calipers.  Very fast & accurate.  I was too busy to take pictures.