Replies

1. 
   IronDog | Jun 13, 2004 07:26am | #1

   Hi Dave,

   I think we'll need a bit more info. to help...

   -What thickness are you resawing the walnut to?

   -What purpose will you be using it for?

   -Is the Walnut properly dried?

   Hitting the sack now, I'm sure there will lot's more advice to come.

   zzzzzzzz......

   Tom

2. 
   vern | Jun 13, 2004 08:16am | #2

   Dave what do you mean a 1"blade or do you mean 17" throat and 1" wide bandsaw blade anyway when something cups that not supposed to [glue ups etc.] before I hit the hay I lay it out on the grass cup side down--cover it up if it looks like rain-- sometimes it goes overboard and you have to reverse the procedure -- then watch it to see where it quits moving -if it is pretty thin - just dampen a cloth and lay on the cupped side for several hours-- keep an eye on it as it approuches flat remove the cloth and clamp it between straight keepers--hope this helps

   making sawdust
3. 
   UncleDunc | Jun 13, 2004 08:22am | #3

   How wide are the boards? How bad is the cup? Is the newly cut surface on the concave or convex side of the boards? Did the cupping happen immediately when you cut the boards or after some time? How long had you had the lumber in your shop before you cut it? Do you know if it was kiln dried or air dried?

1. 
   dwexhler | Jun 15, 2004 12:05am | #9

   Hi UD,

    1) The boards are approx. 8/4 thick and approx 7" wide

   2) The cup is bad. Over the 9' length it cupped about 3-4"

   3) The cut surface is concave (cupped)

   4) Cupping was immediate

   5) I've had the lumber in my shop about 2 weeks before the resaw

   6) I don't know for sure if it was Kiln Dried. I expect it was. I bought it from Lane Stanton and Vance and as previously noted, it was very staight and true prior to the resaw.

   Thank you for your insight and time,

   Dave

1. 
   TomMGTC | Jun 15, 2004 12:10am | #10

   When you say it cupped 4" over 9' it sounds like it bowed. Cupping occurs across the width, and it sounds like it did this as well. Seems like improperly kilned stock to me. Was the effect similiar on both halves of the board only in opposing directions?Tom

   Douglasville, GA

1. 
   dwexhler | Jun 15, 2004 12:16am | #12

   Right, each board bowed over the length, not over the width (cup). I stand corrected.

   Dave

1. 
   Crunk | Jun 15, 2004 12:22am | #14

   I would consider that much bowing beyond unacceptable.  You may have recourse with your supplier.  Take a piece in and bitch a little.   You've got to make sure that you didn't introduce that much bowing during the resawing operation.  If the THICKNESS is consistent along the length, then the piece is bowed.

   Edited 6/14/2004 5:27 pm ET by BossCrunk

2. 
   dwexhler | Jun 15, 2004 12:24am | #16

   After further discussion, the wood did actually bow over the length, not cup across the width. If your comments were for the cupping, could you address the actual bowing I'm having. That is, after resawing, the middle of the boards are about 6" apart with the ends touching.

1. 
   GHR | Jun 15, 2004 01:39am | #17

   When I buy wood, I take responsibility for it. Wood moves.

   I would support it on the ends with weight in the middle and see what happens.

1. 
   TomMGTC | Jun 15, 2004 01:54am | #19

   Interesting. I thought your wood never moved.

    

   From: 

   GeorgeR  

   May-28 5:49 pm 

   To: 

   STRONGBO1

    (5 of 17) 

    

   17949.5 in reply to 17949.1 

   My wood ages a couple years before I cut it. It never moves.

    

    

   View Image Options

    View ImageReply

    

   Tom

   Douglasville, GA

2. 
   GHR | Jun 15, 2004 08:01am | #23

   This fellow's wood moves because it is not aged yet. My wood never moves because as I said it sits in my shop for years before I use it.

3. 
   TomMGTC | Jun 15, 2004 02:02pm | #24

   Sounds to me like his lumber is case hardened and from what I understand, no amount of time is going to remedy the defect.Tom

   Douglasville, GA

4. 
   jackplane | Jun 15, 2004 02:44pm | #25

   Like some others have said, your problem lies in the kiln drying process; the lumber has more moisture on the inside than the outside due to improper drying. Your best recourse in the future if this is a persistant problem is to find another supplier.

     You could set the pieces on wet ground, outside side down for a day and see what happens. Or cut the pieces close to finish length and joint and plane( to reduce stock removal).

5. 
   dwexhler | Jun 15, 2004 07:02pm | #26

   Hard to believe that it's the drying in that the lumber is so straight before the resaw....

   dave

6. 
   jackplane | Jun 15, 2004 07:38pm | #27

   It  may sound hard to believe. Check with a moisture meter if you doubt.

7. 
   dwexhler | Jun 15, 2004 07:54pm | #28

   Will do,

   Dave

8. 
   dwexhler | Jun 15, 2004 03:41am | #22

   I'm already in the process, I'd just like to minimize that need in the future...

   dave

4. 
   Crunk | Jun 13, 2004 10:44pm | #4

   No real way to prevent it.  You can only plan for it.  You must resaw overthickness to allow room for flattening and planing to final thickness.  Anything else is a pure crapshoot that may or may not work. 

   It's almost impossible to have no movement, after all, you have freshly sawn faces to deal with.  The wood will equalize and the cupping will abate to some extent in properly dried stock.  I can count on a few fingers of one hand the times I've resawn stock and it stayed flat.  There always seems to be some movement requiring jointing later.  Don't make the mistake and joint the resawn sections right away.  Let them rest a while.  If a project requires resawn stock that work is done on day one with no exception.  Then I lay out and do rough rips and crosscuts on the rest and then go drink a beer and come back the next day.  Resawn stuff is jointed and planed to thickness usually on the day it goes into the project and usually a minimum of four to five days after the resawing session.  Yep, I'm slow but I don't remake a lot of parts either.  It wouldn't be unreasonable to wait even longer.

   Bottom line is give it time.  If the stock turns into a corkscrew then you probably have a legitimate beef with your supplier.

   
   

   ---

   Edited 6/14/2004 12:29 pm ET by BossCrunk

1. 
   dwexhler | Jun 15, 2004 12:21am | #13

   After further discussion, the wood did actually bow over the length, not cup across the width. If your comments were for the cupping, could you address the actual bowing I'm having. That is, after resawing, the middle of the boards are about 6" apart with the ends touching.

   Dave

5. 
   forestgirl | Jun 14, 2004 12:04am | #5

   I think the first quesion you should answer is "how dry is the lumber?"  Until you know that, you won't know whether the cupping is truly due to permanent ("unfightable" if you will) stresses, or simply due to wood that's got too much of a moisture differential between the outside and the inside.

   Irondog's question "is [was] it properly dried" is important also.  If this lumber was commercially dried and stored properly, you may be able to return it.

   forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
   Another proud member of the  "I Rocked With ToolDoc Club" .... :>) 

6. 
   mudman | Jun 14, 2004 12:34am | #6

   Dave,

     If you put the boards back together at the cut line,  are the boards cupped away, like a banana, or into each other. Or are the cupped in the same direction so that they meet with little or no gap? If the last senario is the case then the problem is the saw not the wood.

   When resawing really tall (wide) boards the blade will curve or bow, causing cupping. To clarify, if the blade is running perfect it is straight btween the upper and lower guides. If the work is not fed into the blade at the angle corected for drift, the blade will curve in the stock, actually cutting a curved or bowed line. Even if the saw is set up perfectly, there will be a little cupping. The taller the stock the more it bows. If this is the problem try  resetting the guides, finding the drift angle, and increasing the tension. FWW did a comparison a while back on blades and this was one of the criteria they judged by.

   If the boards are cupping away or into each other then the wood is either case hardened, or reaction wood, there is no real fix for that.

   Hope I'm not patronizing you, you may already know all this!

   Mike

   please excuse my spelling.

   
   

   ---

   Edited 6/13/2004 5:37 pm ET by mike

1. 
   dwexhler | Jun 15, 2004 12:12am | #11

   The cup is on the resawn side on both pieces, like this: (). Any way you know of to prevent this from occuring?

   Dave

1. 
   mudman | Jun 15, 2004 01:48am | #18

   There was an informative article on the subject of bad kiln drying. Basicly it is unfixable. Something to the effect that the binders that hold the cells together melt and resolidify in a different shape. Pretty deep stuff. The only thing you can do is buy from the best supplier you can.

   Mikeplease excuse my spelling.

7. 
   RonInOttawa | Jun 14, 2004 06:07pm | #7

   Before starting to resaw, a quick skimming pass on either a planer or jointer on both sides of the board will often help to reduce cupping. This opens up the pores and allows moisture to escape at an equal rate from both surfaces.

   Regards,

   Ron

1. 
   dwexhler | Jun 14, 2004 11:53pm | #8

   Ok, Thank you for the tip, I'll give it a try.

   Dave

2. 
   dwexhler | Jun 15, 2004 12:23am | #15

   After further discussion, the wood did actually bow over the length, not cup across the width. If your comments were for the cupping, could you address the actual bowing I'm having. That is, after resawing, the middle of the boards are about 6" apart with the ends touching.

8. 
   arkie | Jun 15, 2004 02:49am | #20

   I have found that getting the wood hot by a blade running too fast and/or dull and a excessive feed rate can cause all kinds of movement in the wood. Patience is a virtue.

   Just my 2 cents.

1. 
   dwexhler | Jun 15, 2004 03:40am | #21

   You may be right on the mark. Any other words of wisdom for a novice resaw guy?

   Thank you,

   dave