Recently ( past few months) when I rip some of my hardwood the two sides of the board converge on the blade causing the wood to pinch the back of the blade. The wood on the left side of the blade seems to bow in more than the wood between the blade and the fence. The result is I can’t rip a board straight unless I rough cut it then make a finish cut of about 1/4 inch or less. The other problem is that sometimes the pinching is so severe that it bogs down the motor and trips the circuit. I’m using a 3HP Unisaw with a Forrest WWII blade. I aligned the fence with a dial indicator and it is properly aligned.
It doesn’t happen with every cut but it occurs at a higher frequency with newer wood. I ‘ve been working a lot with kiln dried 4 through 8/4 cherry.
The only thing I can think of is the temperature, I’ve been working in a barely heated barn in New England and the temperature inside the barn for the last few months has been in the 30s and 40s and down in the teens at night. This is the first time I’ve had my shop in an environment of less then about 60 degrees. The shop used to be in the basement of our old house.
Any help would be greatly appreciated… sorry the message is so long.
Replies
This is wood movement most likely is related to the drying process. It's called "case hardening" and means the wood was not dried properly. If I remember correctly, the inner part of the lumber is dryer than the outer part, and when the lumber is cut the imbalance causes this movement (maybe Jon will come in and give a more accurate description).
You might consider contacting the business that provided the cherry and see if they'll remedy the situation by exchanging the wood. The problem is not likely to be related to the temperature in your work space. Humidity will affect wood, but as far as I know, shouldn't be causing the problem you're having.
Be extra, extra careful when cutting the wood, as having a piece of lumber pinch the blade is very dangerous.
forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
Sounds like you are running into some wood that has not been properly dried or reaction wood.
But, how come your splitter isn't preventing the blade from being pinched. That is the function of a splitter.
mmazzuca
FG and Howie have hit points that should be addressed. I use a moisture meter before a piece of stock ever meets a blade. Even if it was supposed to be kiln-dried, that leaves much gray area as I have personally found.Doesn't always work out that way. With a meter you can detect wetter wood in the center and dryer toward ends and the outer perimeter.
Even with a splitter (are you using one as Howie noted?) it can still mesh back together after traveling past the splitter. My solution when I have wet or squirrely stock is in the pocket of my shop apron. If the wood starts to bind as you noted, I stop the saw and wait for the blade to come to a complete stop. Walk around to the rear and insert a Wedge-It (plastic wedged shim from HD for shimming uneven furniture legs). Continue till the wood starts to bind again and repeat the process till you get her all the way through. Yep, slows you down, but when you finish you still have hands and fingers.
Best fix is to invest in a moisture meter and don't take wet stock to the saw till it is in the range of 8% - 12% moisture content through-out. I also would reccommend a 24 tooth ripping blade. It makes a world of difference, IMO.
Be careful.....
sarge..jt
[PS: Just realized we hadn't explained reaction wood. It is a growth defect (from a WWer's POV) that occurs when a tree leans as it's growing. In such a tree (or limb) the growth rings will not be symmetrical -- they'll be closer together on the one side of the trunk, and the pith will be off-center. This wood doesn't mill well at all.]
Those plastic wedges are real handy, aren't they? That's exactly what I used on some alder I recently ripped a piece off off. Must have been reaction wood rather than case hardening, because it was only a 1+" side section that was weird. The other 7" width cut up just fine.
forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
Edited 4/21/2003 1:16:42 AM ET by forestgirl
Jamie
Yep, the wedge-it's are great. And yeah, wood does some unusual things. When I was building the parts counter weeks back, I use southern yellow pine that was not properly dried to keep the cost down. I had to Wedge-It for over 800 linear feet. I didn't get an inch of bad-tempered wood though, as I spent hours carefully picking rift-sawn lumber. I must have moved their entire stack twice culling flat-sawn and stock with the heart in the center.
My philosophy for ripping is use the proper blade, make the set-up exact, don't stand in the lane, use push-sticks and hope for the best; but expect the worse. I guess if the wood wasn't mysterious, I would probaly have taken up metal working. ha..ha..
Have a great day, m'lady...
sarge..jt
Another alternative to cantankerous wood is to rip it on a bandsaw. Much safer and stoping and starting to use wedges isn't going to yield a ready to glue edge anyway.John O'Connell - JKO Handcrafted Woodworking
Life is tough. It's tougher if you're stupid - John Wayne
John
I agree with the bandsaw, but I tend to stay with the TS. Using the methods I mentioned, I have had only one kick-back in 30 years. I don't mind the wedging personally, as I don't get in a hurry. I joint about everything. I did do it with a home-made set-up on the router table, but I splurged and bought a jointer.
Yep, that BS will get the job done well, especially with ill wood. I sure was eyeing that Mini-Max at the Atlanta WW Show. Nah.... Awful expensive.....well, maybe.. ha..ha..
Have a good day John...
sarge..jt
I dont think the temp in your shop is the cause of the problem you describe. Also just because the lumber is the correct moisture content will not rule out the problem .You also can experience the same problem from wood that is not case hardened , that is a seperate issue. Tension wood or as I learned to call it ( timber bound ) does happen from time to time . It may be from the drying process or from the growing conditions as in the case of side hill leaning or odd growth ring patterns.A prime example of growing conditions is Southern Oak ,also called swamp oak .The swampy type growing conditions can yield lumber not suited for cabinet and furniture work , but southern oak makes pretty good t&g flooring and it is pretty hard. The main problem with your cherry stock is it sounds difficult to get a long straight run . You may want to speak to your supplier and see what they will offer you ,different lumber exchanged would be my choice .Unless you are only using very small pieces bound up lumber can be a disaster.I don't think you are doing anything wrong . good luck
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