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Author Topic: Cant Size and Lumber Size  (Read 12359 times)

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Offline macurtis

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Cant Size and Lumber Size
« on: February 24, 2002, 03:00:47 PM »
Will set up mill monday in local log yard and practice.
I don't know if brain is having a spasam or what.
But i can not for the life of me figure out after I cut a cant
out of a log, what size lumber to cut out of it. I think the
general rule is .707 . 12" log X 70%= 8" cant.
If I wanted to cut say 2x4's out of this and cut each one of
them 2 1/8, then I would end up with not a 2x4 on the last board.
Is this ok and throw this piece in the slab pile? I do not
know if I have asked this question properly or not.
Please give me some advice.     Thanks

Offline Tom

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Re: Cant Size and Lumber Size
« Reply #1 on: February 24, 2002, 03:30:34 PM »
Yep, it's ok to end up with a "not 2x4"  :D  as a last board.  Many of us end cutting the cant with a trim board.  On the bandsaw mills, a trim board may be an eighth or three eighths leaving a 4/4 board on the mill which doesn't belong on the slab pile. You will find that the 3/8 or 3/4 trim boards are nice to keep around for fencing etc.  I don't throw much away till it rots.

Woodmizer has a quarter scale on their board index that makes it easy to size the cant.  the kerf is already figured in.  To keep from making trim boards you would have to make your own scale so you could relate to the top of the cant.

The easy way to think of the eighth ticks is just as a mark.  Don't try to figure x number of 2 1/8 encrements to the top of the cant. Keep the encrements in even numbers.  IE count the number of 2 inch encrements to the top of the cant.  If that comes out to 6, then add 6 ticks (plus 6 more for kerf).  You will have to compensate for trim somewhere whether it is at the top of the cant or the bottom.  I prefer to cut good boards from the top of the cant without paying much attention to the heighth of the cant so I can get rid of bad wood on the way down without worrying about coming out even at the bottom. Just remember to make good boards when you cut one and not become too much of a perfectionist with the math.  You will be working with wood that will be moving and wood that will have flaws so coming out even at the bottom of the cant is a best guess anyway.

My Granddad and Uncle made sourkraut when I was a kid.  Grandmom had a bunch of crocks but there was too much sourkraut so they bought some more crocks.  Then there were too many crocks so they bought some more cabbage, etc.   Eventually Grandmom made them take the stuff out to the garage because it was filling up the back porch.

Some things just don't come out even. :D


Offline Ron Wenrich

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Re: Cant Size and Lumber Size
« Reply #2 on: February 24, 2002, 05:16:15 PM »
I can give you my sawing technique, which you can use or toss.  I won't saw every log the same, but on low grade logs, I saw inside out.  That means I saw to a target size.  I'm also sawing on a circular mill and primarily hardwoods.

I don't worry too much about the size of the log.  I will position the log, and set the tapers.  My first cut should open up to a 4 to 6" opening face.  I will take a few boards, until the grade starts to drop.

If I am turning down (doing a 270 degree turn), then I will do the same thing on the next face.

On some logs, I will turn up (doing a 180).  For small bandmills, this probably turns out better, since there is less edging.  On a low grade log, I will figure a board plus saw kerf for each cut.  

If my target is 9", I will start at 11 3/4" and pull 2 boards and end up at 9", for example.  If there are more or less boards, then you make the necessary adjustments at where to start.  That keeps waste at a minimum, and eliminates an extra cut to size up your cant.  In the course of a day, that adds up on the larger mills.  10 minutes of wasted time a day becomes a lost week in the course of a year.

On larger logs, and better grade, I will pull for 6" face for grade on the first cut.  I usually leave a little extra wood so I can jump back to the opposite side, if the grade is better.  When doing that, I like to take a shim cut, then a board.  That keeps my lumber consistant, and eliminates boards that are thin in the middle and thick on the ends.  If I don't turn back, then I am putting my waste to the middle where the grade is lower.

When I am cutting multiple thicknesses, then I don't worry too much about the numbers at the outset.  For example, my cutting orders for tulip poplar are 16/4 F1F+, 10/4 F1F+, 6/4 F1F+. 5/4 1 & 2 Com, 4/4 2 Com or less.  F1F means that it has to be pretty good on the back side of the board (the side you can't see when you're sawing).  I need a minimum 6" face, and 8' long.  

When you get down to a cant size, then you are acting more as a resaw.  I can walk down to a target size, if I want.

If you want to work with target sizes, start by writing down your target size, then add you board and kerf.  Make a chart.  After you get the hang of it, you'll be able to figure it out in your head on the fly.
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Offline JoeyLowe

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Re: Cant Size and Lumber Size
« Reply #3 on: February 26, 2002, 10:29:44 AM »
Okay a couple more questions.  When you mention target size, what does that mean?  Should I be striving for a target-sized cant everytime?  I'm new to this too and have only three small jobs under my belt.  The first job was a couple of walnut logs which the owner wanted in 2 x anything.  The second job was SYP which the owner wanted in all 2 x 4s.  The last job was "get whatever you can get out of it".  Although I have setworks on my WM, I used manual mode for everything and used the quarter scale.  I opened the clearest face with a minimum slab cut and started sawing for the clearest boards.  After the first couple of cuts, I rotated the log 180 degrees and sawed some more.  My point is that eventually I had sawed all four sides and was left with a cant somewhere between 4" and 12" depending on the logs.  I sawed a couple of the cants into smaller boards, and left a couple of cants for use as beams.  

I know that there must be better ways or more scientific ways of sawing, so please direct me to the proper instructional sources or clue me in!  Thanks. :P
Joey Lowe

"Working towards perfection has to be a part of anything one does.  You've got to put yourself into it." ... Sam Maloof (chairmaker)

Offline Bibbyman

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Re: Cant Size and Lumber Size
« Reply #4 on: February 26, 2002, 12:47:33 PM »
Do you have the Simple Setworks or the Accuset setworks?   I sawed about a half of one log using only the manual mode on our Accuset Setworks and shut it down and went to the house in total frustration.  After doing a little homework and sleeping on it,  we took off using the AutoDown, AutoUp and Pattern setworks for everything but making the first and second face cuts.  Mary has got to where she uses Pattern mode for sawing the whole log.

Will your customer tell you what they want out of the logs or will it be up to you to decide? If they give you a pile of mixed logs and expect you to make the best decision of what to make out of them,  then you've got your work cut out for you.  But, for example,  if they give you a pile of grade red oak logs and tell you to saw 4/4 grade - there is a method to go about it.  If they give you a pile of pallet and blocking logs and tell you they need 4"x mill width resaw cants out of it, then there is another way to approach the sawing.  If they have big logs and want 2x4s out of them, then there is a different way to approach that.  

If you are sawing dimension lumber such as 2x4s, etc.  Then you can fix yourself up a "cheat sheet" with cant sizes that will come out just right and not have an odd size board.  For example, (just set aside kerf for the moment) an 8x8 cant will produce 8 2x4s, an 8x10 would produce 10,  a 12x10 would produce 15, etc. and so on.  So you size up your log and guess what the most likely cant it will re-saw to exactly some number of 2x4s with nothing left over.  This may be fine to start with but after a bit you'll need to make 1x10s out of one log and 2x4s out of the next and so on. It will get to where you'll keep some common sizes that workout well in your head and learn to calculate less common ones quickly.

With your Accuset,  you should be able to program an AutoDown 4", AutoDown 2-1/8",  Pattern 4" all the way to the deck, Patter 2-1/8" all the way to the deck and be able to cut 2x4s all day long.
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Re: Cant Size and Lumber Size
« Reply #5 on: February 26, 2002, 01:01:24 PM »
The Target size is simply what you want to end up with. My usual target sizes are 3 1/2  5 1/2  7 1/4  by random width.

These are my sizes because our board orders are that width. when I am done cutting, we will have a random width can't that is one of those above 3 dimentions. I then send that cant to our gang saw, where in one pass it is ripped on into boards.

If we are not ganging, my target will be what ever the biggest cut is we have. We cut a lot of 7 1/4 by 3s  so that is my ultimate target.  I look at the log, guestimate what is in it, and then start adding boards to my target.  If the log is big enough, and I am not worried about sawing grade, I may have a target that is a sum of my largets cut.

For example, I am cutting the 7 1/4 by 3s, and I think the log is big enough to get 3 out of, my target would be 7 1/4 by 9 1/2.  you get that by adding the 3 plus 1/4 saw kerf plus 3 plus anothe 1/4 saw kerf plus 3.

I know it sounds confusing, but once you pick it up its not. when you are sawing low grade you wnat to think about what you want to end up with before hand, when sawing grade lumber, you only worry about getting the highest grade boards from the log, and then deal with whats left. But an experienced sawyer will also incorporate the first with the second.

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Offline Ron Wenrich

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Re: Cant Size and Lumber Size
« Reply #6 on: February 26, 2002, 03:32:07 PM »
Right now, my target size on grade logs is 3 1/2 x 6.  If the grade isn't holding out, then I will want to split a 7 1/4 down into 2  3 1/2" pieces, or a 11" piece into 3 pieces.

I know I have to work down through the log, so I won't be at 11", but rather 11 1/2".  I don't worry about a little oversize in my cant, the buyers like them that way.

Some other orders I have are 7 x 9, 7 x 8, 6 x 8, 6 1/4 x 10, and then some really big bridge timbers.  They can range from an 8 x 8 to a 10 x 17.

If you're cutting 2 x random width, you can slab your sides, then live saw it.  Live sawing is where you just saw straight down through the log without turning the log.  I don't recommend this in hardwoods, since there is often a lot of tension in a log.  I would have at least one turn.

I did see a Canadian mill that was using this method.  They were using 2 double cut band headrigs and were sawing some fairly small logs, by our standards.  They put the log on the mill, made 3 passes, then flipped the log.  3 more passes and the log was gone.  It sounded like mosquitos in that mill.  All boards were then sent to 1 edger.  Annual production was 25 MMbf, and that was 25 years ago.

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