Edging against a cant - modified the process

[VB-Milling]

@SawyerTed
@Magicman

You guys just gave me the "aha" moment I've been waiting for regarding cant bow.

Up until now, I've been frustrated that no matter how many times I adjust everything, the bunks never seem to be aligned with each other.  Embarrassingly enough, I never thought such a large chunk of wood could have a bow and not touch the bunks.  Now I see that my bunks are fine and the cant is springing when unclamped.  Thank you so much for the explanation and walking me through. 

I do not have moveable bunks, but I am pretty diligent about minimizing the overhang.  When I just cannot minimize it as much as I want, I get crappy lumber.  Makes sense.

Thank you gentlemen  8)

[SawyerTed]

Eventually, if you haven't already, you will see a slab curl up as you cut it off the log.  Sometimes it may curl up a fraction of an inch and other times it will curl up several inches in extreme cases.  


 
That is tension in the log.  In a log like that the cant may move a considerable amount as you saw. That tension will show up in the lumber.  If I continued to saw this log into lumber, the boards would likely bow reflecting the curl of the slab.  If I rotate it 90° the boards will likely crook.  If I recall this sawing adventure correctly, I was sawing 4x4 or 4x6 dunnage out of firewood logs.  I suspect the ends of this cant curled up as Magicman mentioned. 

The best thing to do is stop and think about what's happening and how sawing releases that tension.  Don't do like I did the first few times and say, "Wow that's amazing!" and keep sawing as usual.  

[APope]

Some woods are extra special. I have seen sweet gum that displayed crook and bow at the same time... Kinda like a propeller. I edged it against the wedge of my splitter and dried it into firewood. It burned like it cut... poorly.

[Magicman]

 

 
Or it might do just the opposite and bow up in the center.  They will also lay flat and move to the side.  I have had them to pinch the band on the far end and actually stop it.  When this happens, the drive belt will squall and blue smoke rise.  

[VB-Milling]

The best thing to do is stop and think about what's happening and how sawing releases that tension.  Don't do like I did the first few times and say, "Wow that's amazing!" and keep sawing as usual. 

Guilty!  Today as a matter of fact!

Appreciate the pictures.  Really drives the point home.

[WV Sawmiller]

  I think you're getting/have gotten the hang of it and Ted was spot on in explaining my suggestion is once I make the final turn I clamp lower than the last board I will cut and I do not release the clamp until I have sawed the cant completely into finished boards. I leave a stack of those board on the mill as a "backbone" to edge against, move the side support up against them and stand the flitches up against the other side and saw the bark off the flitches to the width I want/they will provide. As I saw narrower and narrower boards from the flitches closest to the outside of the original log, I remove and stack the boards previously on the cant to adjust the height downward - i.e. I move the finished board out of the way as needed. I still keep enough at all times to provide solid support for the flitches standing on edge. I hope that helps. 

   Thanks guys for the photos and explanations of the wonky things springy cants can and will do. 

    I fully admit my technique will often result in a couple of springy finished boards but they are consistent thickness using this process. Placing the bow up and plenty of weight on top while drying will help straighten them but there is no promise they will ever lay completely flat.

[VB-Milling]

I leave a stack of those board on the mill as a "backbone" to edge against, move the side support up against them and stand the flitches up against the other side and saw the bark off the flitches to the width I want/they will provide.

I really like this approach and I think that was the last piece of the puzzle I was lacking the understanding of so thank you Howard for clearing that up.  Unfortunately for my little HM126, it only has a 7in depth of cut, so the stack I can leave on there is somewhat small compared to your setup.  It sure beats the way I was doing edging though...one board at a time against tall backstops and constantly adjusting them every cut.  Really glad I understand this process now.

[WV Sawmiller]

   I only have a little over an 8" depth of cut so you should be fine. A 6" stack of boards is plenty of support to edge 12-14 inch tall flitches. Good luck. Keep us posted.

[GAB]

Eventually, if you haven't already, you will see a slab curl up as you cut it off the log.  Sometimes it may curl up a fraction of an inch and other times it will curl up several inches in extreme cases.  


 
That is tension in the log.  In a log like that the cant may move a considerable amount as you saw. That tension will show up in the lumber.  If I continued to saw this log into lumber, the boards would likely bow reflecting the curl of the slab.  If I rotate it 90° the boards will likely crook.  If I recall this sawing adventure correctly, I was sawing 4x4 or 4x6 dunnage out of firewood logs.  I suspect the ends of this cant curled up as Magicman mentioned.

The best thing to do is stop and think about what's happening and how sawing releases that tension.  Don't do like I did the first few times and say, "Wow that's amazing!" and keep sawing as usual.  

@SawyerTed thanks for allowing me to use your photo.
Many times when flipping to the last side there will be a gap between the bed rail and the cant.  ie log stress.
If you take a cut 1/2" higher than Sawyer Ted is showing (1/4" or 3/8" might be enough depending on the gap judgement call), frequently the gap between the bed rails and the cant shrinks, then if you saw down the ends will be thicker than they would have been which results in the ends to middle difference being less.  Note: sometimes it does not work to your advantage.
GAB

[WV Sawmiller]

Gerald,

  Thanks for the comment. My proposed technique only works if the cant lays flat on the rails when you make your final turn. If it does not touch all the rails you need to make the trim cuts till it does.

   And as to stress I have had slabs and flitches literally jump off the cant when you make the cut. You know you're in trouble then.

[WV Sawmiller]

I leave a stack of those board on the mill as a "backbone" to edge against, move the side support up against them and stand the flitches up against the other side and saw the bark off the flitches to the width I want/they will provide.

I really like this approach and I think that was the last piece of the puzzle I was lacking the understanding of so thank you Howard for clearing that up.  Unfortunately for my little HM126, it only has a 7in depth of cut, so the stack I can leave on there is somewhat small compared to your setup.  It sure beats the way I was doing edging though...one board at a time against tall backstops and constantly adjusting them every cut.  Really glad I understand this process now.

On further thought here about the depth of cut issue, if you are edging really wide flitches (say 20"+) you can go ahead and still use the intact cant while it is still 12-14 inches tall, edge the wide flitches, then re-clamp the cant as originally described here. At that stage the cant should have enough weight to lay flat.

  I rarely cut boards over 12" wide for most customers (because of their planer width constraints) so edging really wide flitches is not a common occurrence.

[GAB]

Unless a customer asks me to not saw over a particular width then I shoot for the max. I can get.
For one customer this year I sawed some 15, 16, 18, and 20 inch wide boards.  His pine logs were huge.
Customers comment was do you know how much those would cost me at the lumber yard?

Mr. Green:
I have on occasion edged boards like you describe, however I find that it is very time consuming.
I prefer that the off bearers stack the boards to be edged in 3 stacks. Narrow, medium, and wide.
Then load them up to 20 (for 1" material) at a time on the millbed and start trimming.
If there is a piece of equipment with forks available stack on skids to reduce handling time with pieces to be edged.
GAB

[SawyerTed]

@GAB no problem on the use of the photo. 

If I had been sawing usable lumber the technique "may?" have been different on the log in the photo, I don't know.  I was cutting dunnage from firewood logs, so it was mainly four slabs and done.  The slab curling up like it did was a bit of a shock.  Regardless of shoddy technique for getting stable lumber (I've been a poor example before :D), the photo is certainly a good example of how sapwood can cause stress or tension.

[TimW]

Thank Howard!  I finally learned something from you.  It's a good technique.   I will try it next time I saw.
hugs,  Brandi

[VB-Milling]

I prefer that the off bearers stack the boards to be edged in 3 stacks. Narrow, medium, and wide.
Then load them up to 20 (for 1" material) at a time on the millbed and start trimming.

I think there are two approaches now that I understand the process.  Your process would be difficult for people without hydraulics like myself.  It would be very challenging for me to manually clamp more than, say 4 or 5 boards against the stops and sufficient "slack" be taken out of the boards to ensure no movement.  If I had hydraulic clamps, I could definitely see how your method with two people could be faster.

[WDH]

Thank Howard!  I finally learned something from you.  

Something besides how to bait limb lines and how to insult a poor Bulldog?   :D :D :D

[GAB]

I prefer that the off bearers stack the boards to be edged in 3 stacks. Narrow, medium, and wide.
Then load them up to 20 (for 1" material) at a time on the millbed and start trimming.

I think there are two approaches now that I understand the process.  Your process would be difficult for people without hydraulics like myself.  It would be very challenging for me to manually clamp more than, say 4 or 5 boards against the stops and sufficient "slack" be taken out of the boards to ensure no movement.  If I had hydraulic clamps, I could definitely see how your method with two people could be faster.

VB-Milling:
Even with hydraulics I still need to wiggle the pile to get a proper clamp.
Concerning your statement: "If I had hydraulic clamps" My crystall ball says some day you will.
Cautionary note - the calibration sticker on my crystall ball has expired and I'm having a hard time finding someone to check the calibration and put a new sticker on it.
GAB

[SawyerTed]

I don't have a crystal ball but the sawdust flakes at my sawmill seem to agree with your crystal ball! :D

[Magicman]

I think that was the last piece of the puzzle I was lacking the understanding

I hate to break the news to you but thinking you understand will only get you to the next log/cant which will teach you another lesson.  Each one is an individual unto itself with it's own game plan and is perfectly willing to teach you another lesson.


 

You would certainly expect this one to be a bad actor and it was, but I had another today that was perfectly pith centered that had an absolute mind of it's own.  I didn't take a picture of the end because it looked good but...

one end lifted off of the bed rail a half inch.  I continued to saw down until there were only three 1" boards left in the cant before flipping it 180° and

 

taking a cut to bring it back true.  I only lost one 1" board so no big deal.  Sometime you salvage what you can and don't sweat the rest.

The point that I am attempting to make is that this sawing ain't an exact science with textbook rules.

[VB-Milling]

This couldn't have been a more timely lesson...bunks are right next to each other.









At some point, the very large cant (14+ inches) must have slipped off the last bunk and started its downward curl as I took boards off the top.  Very interesting to see what happens to the cant now that I have an idea what to look for which speaks to @Magicman 's point about continually learning from cant to cant and log to log.

[VB-Milling]

@GAB @SawyerTed

Do your Taro cards have a current calibration?  :D

Maybe we should see if there are any FF palm readers 

Maybe if I get the land I want, I might accessorize it with some orange paint.

[Magicman]

I failed to mention it and neither did anyone else, but as a cant rises and you continue to saw, each board will be slightly thicker on that end(s) because they are 'stealing' thickness from the bottom of the cant.

[VB-Milling]

I tried 3 against a cant and was pretty successful.  Then I did 6 against the backstops and it went pretty well.  This was all for making stickers.

[VB-Milling]

I failed to mention it and neither did anyone else, but as a cant rises and you continue to saw, each board will be slightly thicker on that end(s) because they are 'stealing' thickness from the bottom of the cant.

I saw that in probably 75% of the last boards I've pulled off the bunks, but failed to realize what was happening.  I kept chalking it up to my trailer and my rails being less than perfectly aligned.  But now that I've added rail adjustment and checked it a hundred times, I'm realizing how the cant's reaction to taking boards off the top is affected the lower boards.  Good lesson

[GAB]

I failed to mention it and neither did anyone else, but as a cant rises and you continue to saw, each board will be slightly thicker on that end(s) because they are 'stealing' thickness from the bottom of the cant.

Mr. Davis:
You are correct.
Another thing to consider is to not have too much unsupported overhang from a bed rail as that can result in droop.
Droop for me has caused thin ends and thick middles except for the last board which is the opposite result.
When turning to the last side I try and slide the cant on the bed rails hoping to slide out any sawdust or bark or whatever might be between the cant and the bed rails which can and will result in thick or thin sawing.  (HI Percy)
@VB-Milling I hope we aren't boring you too badly.
GAB