Hi new here. My woodworking experience is 80% residential construction, including cabinet making. My main hobby, aside from fishing, is doing workshop projects. I've built several boats over the years.
I expect my question makes me look like very nerdy, but I have to ask:
I've been ripping lumber for several decades, and the normal outcome of ripping one board is strong warping of the two daughter pieces. I've been putting up with it.
Is this because my circular blades need sharpening? I'm using a 12' 60 tooth. I know it needs sharpening to be perfect again.
The tablesaw fence is indeed parallel to the blade.
Or, should I get myself a large bandsaw to rip boards?
The warping is likely caused by the stresses in the material you are ripping, not the tools/method used to rip.
There are many here far more knowledgeable on this than I, but the simple point is that when a board warps while being cut, that is a sign of improper drying. Cutting/ripping changes the stresses and the material moves to accommodate the new stresses.
Properly dried material should, in general, NOT warp when cut.
When lumber goes sprong right after ripping it is because it has tension locked in it, often from drying to fast, but occasionally from the way the tree grew. This problem is common in dimension lumber because it is always dried too fast. (hence the carpenter joke)
If the lumber goes sprong after few days it is because the lumber wasn't dry before hand. This problem is common in dimension lumber because it is always wet. (hence the carpenter joke)
Take up making furniture with properly kiln or air dried hardwoods and you will never have this problem again.
In addition to what the others have said, occasionally kiln-dried lumber will warp when you cut it.
Is there a way to prevent it - sort of. Look for quarter sawn lumber - I've had better luck w/ quarter sawn not warping than any other. I also let my lumber acclimate to my shop before I work it. I don't know if this really works, but it seems to do so .
Bill, I have had (of all species) one piece out of a lot of Eastern Red cedar that "sprung", when the rest of the lot had absolutely no issues. I was into a rip about 3' when this piece popped open about 5 or 6" at the ripped end. It actually scared me the action was so violent. I have also had a few spring and pinch the blade hard enough to stop my 3 hp Unisaw. I was using a Grr Ripper and managed to hold everything and shut off the saw but had to pry the board off the blade and drive my splitter out of the groove. Last time this happened it was in 5/4 white oak, the rest of the fairly large lot was fine. Guess it could have been what you said about too fast drying as the oak board could have been on the outside of the stack, but don't think red cedar would be nearly as likely as oak to be a problem drying. Most of my wood (not the Eastern Red Cedar) was acquired at estate sales of Amish or Old Order German Baptist's. They usually have excellent wood as they can pick a tree from the middle of a woods and after felling, pull it out to their saw mill with horses. They also are very good in their practices of air drying wood.
I don't think you'll find a 60 tooth 12" rip blade
Keith Newton
You're probably using a finish blade, or combo at best, since you don't give us much to go on. A rip blade will be 30 - 40 teeth, with flat top grind, and 15* hook. The fewer tooth count allows faster feed rate, which you should utilize because a large chip takes the heat away with it.
If your using too many teeth which have a low hook angle, they are scraping very fine dust, which generates lots of heat in the kerf. This is not good for sawblades. There are lots of chemicals and resins that vaporize or melt at high temps, and will quickly build on the side clearance angle of the blade, providing more friction than if just the front edge and top were all that were touching.
When the cut is finished and those two warmer edges are exposed, the local heat could cause some faster evaporation of the moisture in the wood. However wood doesn't change much in length with moisture change, so the stress might already be grown in.
Some general information not necessarily in response to your binding experience
In a modern kiln the wood at some time is hot and wet. This condition plasticizes the wood and relaxes any stress built up from initial drying or from some aspect of tree growth.
Air drying is uncontrolled. In many cases air drying will occur at a slower rate than in a kiln, but not always. In hot dry summer conditions oak will air dry too fast and thick oak may nearly always dry too fast. It is possible to case harden oak while air drying. The point to be made is that air drying does not ensure "properly dried" lumber.
On the other hand modern large kiln operations have several hundred thousand dollars of lumber at risk at any one time in kilns. One can be sure that the company takes every precaution to control the drying to yield lumber that is free of KD defects. But I am sure there will be the occasional board that is an exception to the norm.
there is an old saying that "wood is the most imperfect building material". It shrinks, warps splits, and at its best it continues to move from season to season. It is a mystery why anyone would choose to build anything out of wood when there are other better behaved materials available, but that's us in a nutshell isn't it? As wood workers we love a good challenge and what greater mystery is there that what does the inside of a tree look like?
Growing conditions are at least as great a cause of internal stress in lumber as improper drying. Trees that grow on hillsides, those that have been hit by lightning, those wracked by high winds and those that have suffered wild variations in environmental conditions can have internal stresses that result in warping when released. More often than not warping from these causes is clearly apparent when the logs are milled into lumber, but not always. Sometimes those stresses hide in perfectly innocent-looking boards and reveal themselves to our surprise and dismay on the saw table.
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