Just curious how close to perfection your mills get? While milling dimensional lumber are you guys with 1/32 of perfect? and 1/8? + or -. I have a home built mill and curious what is actually achievable. I saw some one post the other day that even the $30,000 mill aren't perfect if you want perfect get a planer. So it just made me wonder. Thanks!
As far as the sawmill's accuracy, I can not measure any difference between "Setworks" sawn boards. I often have customers that will try, and I just laugh.
Now that is sawmill accuracy. A cant moving as stress is relieved will take you to task. :-\
Logs move, set works hit the numbers, logs/cants move, it's green stock. Many factors can control timbers on the mill, but slight variations should be expected,
Its called rough cut lumber for a reason. With good logs sharp well set band/saw 1/32 is practical with some care from the sawyer. Real world expect a little more, but that's no excuse for sloppy milling. Frank C.
I think you are more asking about repeatability than accuracy? My Woodmizer LT15 is very repeatable. With clear wood, they are very repeatable. Hard knots can cause a wave when you are milling. Sharp band and going slow will help. But if you don't see it ahead of time, you'll make a wave. The beam planer really comes in handy there. If I get a wave while milling, I simply run the planer head over it to flatten that cut face. Then continue sawing. Accuracy to me means how do the boards come out compared to the scale on your mill. To tell the truth i haven't every done an truly scientific experiment to evaluate this. I know it's pretty darn close. I always planning to plane to dimension anyway.
My mind went to framing lumber when the OP stated "dimensional lumber". That is about the only lumber that I saw that is used as it comes off of the sawmill. No sizing or surfacing. Accuracy = uniformity.
Repeatable accuracy is no problem on my mill . As stated before stress in a cant will indeed affect dimension .
rough lumber is rough lumber, I get my lumber very close on the most part but never perfect, you want perfect , get a planer
I've checked w/ the tape measure.. but never have taken the Caliper out to check.
Could be interesting..
(https://forestryforum.com/gallery/albums/userpics/31193/20150322_112055.jpg?easyrotate_cache=1438832629)
I expect accuracy of +/- 1 mm.
I'll settle for +/- 1.5mm (about 1/16" )
If 3 boards in a row come off with a 3mm variation I go looking for a fault.
Log stress and cant movement are only issues if you want an excuse. I've built a business on the supply of straight dimensionally accurate GOS lumber cutting some of the toughest species in the world: inability to deal with log stress is an equipment and sawing pattern failure, nothing more, nothing less.
But as stated above, if you want perfect get a planer. My planer just gets an easier ride then most.
LL,
Please update your profile with your equipment used if you don't mind. I am interested in what kind of equipment you use to get this kind of performance. I'm like Lynn and get good repeatability using my setworks but I do have occasional issues with the stress causing a less perfect board. In my case I am depending on the weight of the cant to hold it down while other mills have teeth to hold the cant down better. The board/flitch may jump off when cut but still stays the same thickness.
I saw many Mbf of framing lumber for homes each year. I have one now that reported back to me Monday that he will have no building permit restrictions/issues regarding using "rough sawn" so felling and skidding is his next job.
There will be no planeing or resizing so consistency is a requirement when your lumber will be used for home building.
Once and a while I will get a thin or thick board when using accuset. Normally last boards off of cant. Could be stress, or got busy and forgot to clean sawdust off battery box or sawdust under cant. Dry mast rails or sawdust caught in the up down chain will cause jerky drop and effect thickness.
All the lumber on the circle mill I run goes through the planer . Therefor I get lazy end to end will be within a 1/16 . size will vary up to an 1/8 . Any thing over 1 3/4 will plane out to 1 5/8 . I can do better but it will affect production .
Ya, I'd say 1/16" is more practical, but a 1/32" is achievable... logs move, sometimes unpredictably. Typically there is always a more "critical" dimension (eg. the 4" width of a framing member is more important than is 2" thickness), so try to get that critical dimension close.
I've been a finish carpenter on many jobs were the walls were about as straight as a drunk's driving... and that was using kiln-dried lumber. So I agree with Lynn that sawmill repeatability yields consistent lumber, but people have done far worse starting with much better framing-wise.
I have a homemade mill and my height adjustment is controlled by a winch with stops so each click is around 1/16 so I can't get closer than that. When I am actually cutting I consider it good enough if the blade doesn't wander more than 1/16 above or below where it is supposed to be. To get more accurate I would have to replace my winch with a worm gear winch or replace the cables with lead screws. I could also be more careful when setting up the mill to make sure it is all perfectly level and on the same plane, I use a cheap 4 foot level and am not sure just how accurate it is over the length of the mill. At the moment I don't see the need to make it more accurate, in the future I may come across a project that needs more accuracy and then I will see what I can do to make it better.
I sawed for one person how also had a pile of lumber stacked sitting there that was sawn on a woodmizer and by the looks of it the operator of the woodmizer either didn't know or care how to cut straight lumber. It was full of waves and different thicknesses and made the lumber I made look really good in comparison.
Thanks for all the responses. Was more curious per board variation than repetition. I would say my good boards that I produce are + or - an 1/8" which is ok for what I am using it for at the moment. But was curious what other people label acceptable.
Quote from: JRWoodchuck on March 17, 2017, 06:02:27 PMmy good boards that I produce are + or - an 1/8"
An eighth of an inch would not be acceptable to either me or my customers because I only do custom sawing.
you can saw perfect lumber all day but a 12 wide pine board can shrink half an inch or more depending on the moisture content and even the ring count. with that said my saw works off dogged sizes so i can repeatedly make the same thickness boards over and over, however that system has its flaws too. i shoot for 1/16'' and no waves ;D
My older LT40 always seemed to cut a little thin using the aluminum scale it came with. I started checking and the scale was made with a 1/6" allowance for kerf.....not enough.
I turned it over and made new engravings that allow for .100" That should be closer but I haven't sawed enough to check it yet.
I also made up a scale with markings for dimensional lumber.
There are three things that come together to produce accurate & consistent lumber, more accurately these things each add variations to the lumber.
The mill; when set up right and maintained, the mill adds less error than either of the other two.
The operator; a good operator can partially compensate for mill & log issues.
The log; crooked logs make crooked lumber. Knots may cause the blade to wander and the wood around them will distort while drying, resulting in poor quality material.
Primarily cutting Western Larch (Larix occidentalis) that is mostly clear and quite straight so knots and grain aren't typically an issue. Iam not very experienced with mills in general. The only mill I have ever touched is the mill I built. So their is very good chance it is caused my the operator. But it being a homebuilt mill there is probably even more chance that it is the mill and or a combination of the two! But from what I have gathered inconsistencies in the lumber thickness are preventable. So I will continue modifying my mill so that those inconsistencies are fewer and further between. Thanks again for the responses.
Here is a thread from 2003 where we had a thin cut competition. Give it a try.
https://forestryforum.com/board/index.php/topic,2187.0.html
https://forestryforum.com/images/YaBBImages/userpics/ThinWoodWillow.JPG
https://forestryforum.com/images/YaBBImages/userpics/ThinWood.Light.JPG
I'm not sure I can't get these pictures to embed?
I think Den-Den has the right of it.
Equipment choices can make a huge difference. Wide bands are stiffer then thin bands so less inclinded to wander in the cut around variations in timber density. Circles are stiffer again - though tuning and setup on a circle saw is very important as to whether it cuts a clean finish or a rough one, some of the worst boards I've ever seen were cut with out of tune and/or misaligned circular saws.
The machine design is also important. A saw with a linebar is more consistent then one without. We run a circle rack which is more accurate then that again. Sash gangs are super accurate. It's all about the interaction between sizing mechanism and wood... some saws cut straight lines regardless of what the log does and some cut a consistent space between log and sizing mechanism that means the board is consistent regardless what the log does, though it also means you can cut a curve into the board you produce.
A lot is operator. How sharp the saw is, how dialed in the equipment is, how much variation the operator accepts as normal before they start looking for a fix. We've gone over this before in other topics but I can sit all day on 17/16" to get a board that finishes at 7/8" for the cabinetry trade, while most here would sit on 5/4 or more. The reason I can do that is because my equipment choices mean I can cut to a closer tolerance because I get less sawing inconsistency then most equipment does. From my point of view that accuracy helps offset the kerf loss we wear cutting to that degree of accuracy.
And a lot is log but its more "experience with" logs. I've grown up cutting springy eucalypt. My cut patterns often tend to be quite different to that used by most here because I'm used to dealing with so much log tension. I accept a far lower recovery rate as normal to most here also, because I know I have to trade fibre for accuracy and straightness in a springy log. When I shift the cut patterns that allow me to do that across to wood thats more in the average range for tension I'm almost lost... I get all happy watching things happen when I dont have to fight the log for every last bit of wood, like a stray dog getting tossed a rump steak.
You never learn to deal with bad logs by cutting good ones thats for sure.
And I think a lot is mindset. Some are happy with average, some want to be better then average. Most of our framing hardwood is sold rough sawn - thats normal here. My thing has always been that i'm a little mill, but that means I'm producing a better product then the big guys, as opposed to using that for an excuse for mediocrity. Nothing wrong with being average BTW, average is usually cost effective which is why its the average. But my way of competing in that market has been to be better then average, and take it to them on quality because I sure as hell cant take it to the big guys on cost of production.
That mindset about how close to perfect you wish to be often determines just how much effort you put in and how much playing around you're prepared to do to produce a product. I'm a perfectionist, and I look at my product with a critical eye which means I strive for greater precision then most.
I can consistently cut accurately, board after board. If I have a log with internal stress, it takes longer to saw because I have to turn the cant more often, occasionally after every cut. And no, I don't have accuset but that doesn't keep me from being just as accurate as the mill that does. After you do it for a while, you can drop and stop exactly where you want nearly every time. And if you miss, just tri again.
So in answer to the original question, my accuracy is within 1/64.
If you are off and saw the board 1/32 thick, then the next board will be 1/32 thin. This makes a 1/16 difference between the two boards so you are + or - 1/16 ". If you miss by 1/16", then you are plus or minus 1/8" when comparing board thickness. But you are + or - 1/16" from wanted thickness.
The reason I posted this question is I am a bit of a perfectionist. I only saw for myself at the moment, maybe someday I will saw for others. I don't feel comfortable with the quality of my boards to saw for others yet. I have read multiple times on different threads don't expect perfection it's a bandsaw mill. But you all have answered my question that it is possible (I would consider being within 1/64th pretty stinking close to perfection) so I will keep chasing it trying to dial my mill and my skills in better. Thanks again for everyones input.
I can saw with accuracy of 0.0000000000000001", but only if I perform the ritual EZ Monkey Dance before each cut. :D 8)
life's too short to be perfect...strive for perfection, but be happy with industry standards. i know theres specs for rough lumber but i havnt had luck finding it. the NELMA stuff ive dug up so far is all for surfaced lumber....i know its somewhere in my pile...... :P
Quotelife's too short to be perfect...strive for perfection, but be happy with industry standards
This ^
When they start growing perfect trees, maybe I'll worry more about extreme accuracy. Doesn't matter how good your saw is, if you take a board off a cant, and the whole cant bows by 1/16", at some point you have that inaccuracy. Sure you can flip the log and reduce that, and have things go 1/16" in the other direction. And a good sawyer will do this or other tricks to maximise their accuracy.
But that wont change the fact that the boards vary by 1/16", and this is why it's considered acceptable. If you want more accurate, then you need to get the wood dry, stable and plane it to final size.
Heck you are going to get that much variation in size as it dries, depending on radial or tangential grain, and then throw in a few knots (that don't shrink in length)
Now working to minimize inaccuracies is a good thing, but getting hung up over any minor imperfections is going to drive you nuts, because they will happen, no matter how good your mill is.
The minor imperfection I am trying to remove are variations in the thickness of individual boards. Not caused by knots or bad logs. Where my blade climbs or dips through the length of the cut. Just mainly wasn't sure if that was "normal".
Yours is a worthy goal which if always kept in mind will improve the consistency of your lumber and the quality impression people have of your work. smiley_thumbsup
It can also drive you nuts sometimes. :-\
what are people building where the rough lumber has to be that perfect ???
Caring about whether they're 1" or 1-1/16" is the key to making sure some of them aren't 1-1/4", when it matters.
Green sawn accuracy is very important if you're building with green timber because if you've got timber thats reasonably straight - or at least bowed but not sprung (bow you can easily pull out with a clamp, spring makes for a battle)- and evenly sized it makes for faster building. You've also got to factor in shrinkage variation: if you've got say 3/16" variation in green sawn size and then pick up another 3/16" through variable shrinkage .... all of a sudden that dead straight roof line has dips and curves that are noticable.
My equipment is very accurate - I literally expect sub mm precision which equates to 1/25 of an inch more or less. And it delivers time after time. So I dont have to worry so much about the thick and thin stuff... each board is forced to the fence by the hob and the saw sits in the middle. But my gear will cut a precisely accurate thickness board with a curve like a banana in it quite happily if thats what the wood wants to do so we still have to face (shim) cut back to a straight line as required.
If you're using gear like a band or a swingmill then you start running into the thick and thin issues, and as pointed out if one board is scant you can mostly expect the next one to be oversize and vice versa. And the solution is really simple... if you cut one board and its thick or thin... face cut. Dont compound the error and make it one skinny board one fat one.