Replies

1. 
   Scott_y | Aug 05, 2007 07:13am | #1

   The wood itself could be moving. Internal stresses are released after cutting the wood.

   Try some quartersawn or a different species to see if you get the same movement.

   Scotty

1. 
   BG | Aug 05, 2007 11:01am | #2

   Scott,
   Most of my projects have been with quarter sawn stock that got me wondering in the first place 'How could this be happening'. The experiment was flat sawn and a pretty new Forrest II blade. It's almost a perfect spring joint and a few plane strokes on the ends eliminate the gap. Perhaps I should try a piece of plywood?

1. 
   SARGEgrinder47 | Aug 05, 2007 05:57pm | #4

   Morning BG..

   'How could this be happening'?.. bg

   Internal tension released (and even with quartersawn in white oak).. Arbor run-out.. possible fence movement by un-even pressure during feed.. dulling blade.. un-even tension applied by hold-down used left of blade.

   "Perhaps I should try a piece of plywood"?.. bg

   Perhaps.. but not a true guarantee of not having tension in it. I purchased a small panel yesterday to rip down to build a shipping crate to send Bob from Kidderville a mortiser. Not particularly dry as it was a top piece and they had just opened a bundle. But... good grade ply would be a better test than oak as it is cross grain laminated.

   It is most likely internal tension being released. If you had checked the oak with a moisture meter in advance, I bet you would have found it was dryer toward the ends that meshed for you. It basic release of moisture is through the end grain leaving the middle wetter and more likely to sping.

   How could you resolve the problem if indeed run-out.. dull blade and no un-normal tail fence movement? You already have IMO.

   "It's almost a perfect spring joint and a few plane strokes on the ends eliminate the gap".. bg

   I wouldn't be overly concerned, BG. Wood is going to move and certain species more than others. Wet wood more than properly dried etc.

   Your best solution IMO since you already have the solution is to realize it's not of major concern. I would suggest you use the time more wisley to run to the store and stock up on pan-cake mix as it could possibly be a very cold New England winter and I am aware of your more prevalent concerns if ya get snowed in and you develope a case of cabin fever. ha.. ha... ha..ha..ha..

   Regards...

   Sarge.. john thompson

    

    

    

2. 
   highfigh | Aug 05, 2007 05:41pm | #3

   Draw a line parallel to where the cut will be, 1/4" away, using a straightedge. After the cut, sight down the line and see if it's straight, or not. If it's straight and the cut is an arc, it could be wobble or play in the arbor. If the line is an arc, it's from internal stresses.

   It's part of the reason we have and need jointers. There has never been any guarantee that the wood will stay straight after cutting.

   "I cut this piece four times and it's still too short."

   
   

   ---

   Edited 8/5/2007 10:42 am by highfigh

3. 
   forestgirl | Aug 05, 2007 06:27pm | #5

   Hey, BG, it's a pain isn't it?  When that happens to me, it's usual due to one (or both) of two reasons:  (a) My technique is off (using a featherboard helps greatly!) or (b) the back of my fence is moving.  My last project, I took one of those magnetic dial indicator bases and anchored it to the outside of the far end of the fence to keep the fence totally stable.  It really helped.

   forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-) 
   
4. 
   oldusty | Aug 05, 2007 06:31pm | #6

     BG ,  

             My first impulse is the edge you used against the fence may not have been straight whether it was sawed or jointed . It does not sound like your fence or your blade .

          How are you making the first edge straight ?

          That edge is certainly a reference and an indicator of results produced in most cases . Is your stock straight line ripped when you get it ? it is not always perfectly straight even then .

                    regards            dusty

5. 
   ring | Aug 05, 2007 06:33pm | #7

   Do your experiment on a sheet of MDF to find out if it's the saw or the wood that is causing the bow.

   David Ring

   http://www.touchwood.co.il/?id=1&lang=e

1. 
   BG | Aug 05, 2007 09:14pm | #8

   All,
   Thanks for all the ideas. I went down prepared to try everything you all had suggested (made pancakes too)and grabbed a piece of MDF to begin. End of story, the mdf came out perfect every time...so it must be wood movement.
   Would it be a good guess that the internal moisture is higher in the middle than at the ends of the stock, ergo, the movement and after a while it may relax back to being perfect? Or is it more likely to be stress and stay bowed...this is all stock that has been givn tme to adjust to the new environment and tested with meter...6-8% moisture

1. 
   SARGEgrinder47 | Aug 05, 2007 10:56pm | #9

   Afternoon BG...

   Would it be a good guess that the internal moisture is higher in the middle than at the ends of the stock, ergo, the movement and after a while it may relax back to being perfect? Or is it more likely to be stress and stay bowed...this is all stock that has been given time to adjust to the new environment and tested with meter...6-8% moisture"... bg

   I think either could happen as it's wood and going to move over it's lifetime in relation to weather regardless of how well you sealed it. But.. you mentioned oak and with that said, having used a lot of white oak;  I would almost bet it will return to normal and show minimal movement on the future. White oak in my experience (and I am not as familiar with red oak) usually doesn't get too squirrely in it's life-time of transition. 

   I would proceed with caution if the entire length is 6%-8%. I have never seen any stock that was the same moisture nearer the middle than at the ends. But.. if it were indeed 6%-8% in my region, I would wait till it averages the length of the stock around 9% - 11% with 10% perfect.

    The 6-8% figure is just too dry to seal here in Atlanta, IMO. Here a better average to shot for is around 11%-12%. The closer you get to 10% here gives it a range that I found it will seek seasonally which is from 6% to 14%. 6% with dry heat in winter and 14% with humidity in summer. I personally feel sealing at 6%-8% here would be asking for potential "trouble" down the road..

   Good luck with whatever project you have working...

   Sarge.. john thompson

    

   Edited 8/5/2007 4:03 pm ET by SARGEgrinder47

1. 
   BG | Aug 06, 2007 12:34am | #11

   Sarge,
   It sounds like there's a whole lot more to know about moisture meters and using them effectively. I bought a very inexpensive model on sale at Rockler about 2 months ago. The instructions told you how to put the battery in the back, period. I've wanted one for a long time but it kept loosing out to other priorities. Also, the price range for these things is significant without real distinctions in utility/quality.
   I wanted one to evaluate glue-ups and appropriateness to begin finishing. Some people use them for calculating the right size for drawers.
   Do you know of an article or an instruction on using? thanks

1. 
   SARGEgrinder47 | Aug 06, 2007 02:47am | #12

   Evening BG...

   There are a wide range of them and I certainly can only speak for the sensor and pin type I have. I use the sensor on stock that has gotten close to cured and the pin at the lumber yard - mill, etc. I like how the pin type gets to the root of matters at the mill or yard to know just where the starting point will be on stock I may potentially purchase.

   I know of no articles but suggest you Google as someone out there has something on-line I"m sure. I learned to use them from some folks at Highland WW and kind of ad-libbed till I had it figured out. The main key is Don't take a reading at an end and assume the center will be the same. Attack all angles and get a mean average.

   And you will notice that moisture content can change radically over-night. We had a short drought here in early summer. When the bottom finally fell out... 3% difference in reading average the next day. Kind of like rust with cast iron. Give rust any opportunity and it will attack quickly. Same thing with moisture content changes I have found.

   Regards...

   Sarge.. john thompson

2. 
   SARGEgrinder47 | Aug 05, 2007 11:09pm | #10

   Afternoon David...

   "Do your experiment on a sheet of MDF to find out if it's the saw or the wood that is causing the bow".

   David Ring

   ******************************************

   Sometimes things are so simple, you over-look them even when sitting at the end of your nose! I realized that fact as I read your post!.

   Excellent idea using MDF which is within .004 flat and stable right off the shelf!

   Regards.. .

   Sarge.. john thompson