Tablesaw feed questions

[Mark Visconti]

I'm using a sawstop 3hp (the one before there was a contractor saw). I'm ripping home depot 2x10s and 2x12s. I have the riving knife and kick back pawls installed. All boards sat in my shop for two+ weeks.

Boards are jointed and planed one side. I've had a few warp while being cut that I have stopped and then hand cut. Question on that in a bit...
This last board was pinching together and pushing the board back at me. I stopped and took a look, but the pinch doesn't seem overly strong compared to some of the others I've watched do interesting things.



What's the best technique during the cut for safety when this occurs? Just stop the saw and remove the board? The temptation to power thru it is strong, but I've heard the saw sound change a few times on this lumber and have just stopped the cut to be safe.

I don't buy much framing lumber and while I have worked with it before, I havent really experienced this strong of behavior before. Is this a technique issue that just hasn't exposed itself while cutting dryer wood? Maybe I screwed up my fence alignment and did not realize it? Most of it has cut fine. I am seeing some wood movement during the cut so possibly wet boards (my moisture meter is nowhere to be found).

Edit: just had another board do it. Appears to be a slight pinch after the cut that causes the board to rise up towards the top of the blade which is how I understand traditional kickback occurs. I expected the rise to be stronger, but it's a slow rise and push towards me.

Thanks!

[Steve Eure]

There is a lot of stress in some of the wood that comes from box stores. Could be that the wood is not completely dry and they mill this lumber to make the most money, not necessarily for the best product.
I've dealt with is problem that you are experiencing by placing a flat head screwdriver in the kerf immediately after the riving knife. Be careful with twisted boards, but this method tends lo work. It does help to have a helper to place the screwdriver in so you can concentrate on the cut.

[michael dilday]

When I have a stressed board that binds the blade I pull it out and start a new cut. That normally cuts away the previous closed cut and I can proceed.

[Doug Garson]

How about putting a featherboard pushing the workpiece down behind the blade? That would prevent the piece from being picked up and throw back at you ie kickback. With that in place the worst that could happen is you overload the motor and trip the breaker or motor overload. Board buddies would be even better but featherboards are an easy shop made solution.

[Rod Sheridan]

Step one for solid material ripping is to use a short fence that ends just beyond the front teeth of the blade.

Step 2 is to use a rising knife which you are

Step 3 is to use a blade guard.

Some wood just has lots of internal stress, often this wood is suitable for the fireplace....Regards, Rod

[Mark Visconti]

I am using a blade guard which may be saving me as it might be why the board isnt getting on top of the blade.

Thanks for the input. The boards are cheap enough that I will just get another and use the problem board for a different width rip. It forced me to order a new moisture meter as well.

[glenn bradley]

You’re getting a good demonstration of big box lumber versus lumber processed by a company or group of companies who know how to handle quality lumber. Dimensional lumber, even kiln dried, is generally too wet to be reasonably stable. As an example, I made a bench base from KD 2x12 material that had acclimated in my shop for a month. The base still continued to move for a few months after. I switched to poplar from the lumber yard. Not only was it cheaper (since I had much less waste) but, that workbench and base are still in service along with another built since.

The nature of big box dimensional lumber makes it fairly unsafe to cut it on the table saw IMHO. When I need to rip this kind of stuff I use the bandsaw. Do you have a bandsaw available for your use? Once the board has been ripped to with you can then joint the face and that edge and process the material like usual.

[Jacob Reverb]

If the kerf is closing on the blade while I rip a board, I will sometimes stop the cut, then reverse the board and cut from the other end. You need to be careful when the new kerf meets the old kerf, but it can help prevent a kickback situation caused by the wood clamping closed on the blade like a brake caliper...

[Richard Coers]

Ripping on a band saw is the safest way to work box store construction lumber.2 weeks in your shop is just a start for that stuff. I've seen it at 20% moisture when I bring it home.

[Lee Schierer]

Two weeks is not sufficient to reduce the moisture in the interior of a 2 x 4. You are wise to stop your cuts. One cause for boards climbing up on a saw blade is too many teeth on the blade. When ripping construction lumber use a dedicated ripping blade. If your boards are climbing up the blade you should raise the blade higher so there is more down force on the cut. You can use wooden cabinet leveling shims behind the blade to wedge the pieces open, but you must turn off the saw each time you want to add a wedge.

[Jim Dwight]

I like to use a wooden wedge in the kerf when the wood wants to pinch the blade. My PCS only has the 1.75hp motor and I have had it stop the blade. It isn't just dimensional lumber that does this. My blade stopped ripping an old stair tread I was repurposing. It was several decades old and was laminated. But it still warped into the blade. Flipping the board around also works.

I think the SawStop riving knife is part of the issue. It is a compromise thickness so it works with thin kerf blades and kind of works with regular kerf. I haven't done it yet but plan to make a 0.1 inch thick riving knife. With a thicker riving knife, wood could not pinch the blade as much. I had a .1 inch riving knife on my BT3100 and did not have the issues I have had with the SawStop with wood pinching the blade.

I use construction lumber for furniture but I realize it will not be dried like furniture hardwood. I've read it is normally dried to 12% moisture. But I have not had problems using it - or at least not problems I don't have with more typical furniture wood. I am not sure when I will get time but I plan a new dining table with a softwood base died black and a cherry top. I will pick out 2x12s at HD for this unless the 2x10s look better. I will look for Southern Yellow pine. Usually wider boards are clearer - or have more clear areas. Longer boards are also typically better.

[William Hodge]

I use framing lumber from Home Depot for set up pieces, glue forms, temporary benches, etc. A few 2 x 4 pieces glued up are cheaper than a 3" x3" piece of hardwood.

The lumber on the outside of a lift is usually drier,and the top row of a new lift is the best. I bring a moisture meter. Sometimes the wood in a different dimension will be better and drier. The longer wood is often better. The bottom of a lift of lumber can have grit embedded in it from dirty forks on the fork lift.

[Mark Visconti]

Thanks all. I thought about the bandsaw technique as yet another reason I need a bandsaw...

Regarding the Big Boxb lumber, I actually need relatively small cross sections (3 × 1.25" and the like, but bought 2x10s and 2x12s because they usually are better than the 2x4s and 2x6s. The large boards seem to have less twist and are generally more straight).

Yeah, I have the blade all the way up (with blade guard covering it).

While I do get a good amount of waste, the lumber is amazingly cheap. I have two lumber companies nearby the I am going to check, but I suspect it will be 3-5x+ as expensive. I'm building shop tables and storage so I can live with knots and pretzel lumber. Although probably cheaper to get some decent lumber than an emergency room visit.

I only need a few more cuttable pieces and my cutlist will be done.

[Lee Schierer]

Yeah, I have the blade all the way up (with blade guard covering it).

What blade are you using? A dedicated rip blade I hope.

[Robert Hazelwood]

Construction lumber can be useful, it is really cheap and readily available. But it will tend to move more when doing the initial stock breakdown. This is a perfect job for the bandsaw, which handles wonky wood with much less drama. Even kiln dried hardwoods tend to move some when making cuts that remove large amounts of material, so I do all stock breakdown on the bandsaw. Only use the TS for ripping down to final width after all stress is released, on pieces that are too wide for the planer (otherwise I just use the planer).

If you only have the TS, maybe you can get a riving knife that is thicker? If the knife is designed to be work on thin kerf blades and you are using a full kerf blade then the knife is a good deal thinner than the kerf, so it doesn't keep the pinching kerf off of the blade. Another way is to put a wooden splitter on a homemade insert plate that closely matches the rip blade kerf.

[Mark e Kessler]

I put a wedge or screwdriver in the kerf and motor on...

[Lee Schierer]

I put a wedge or screwdriver in the kerf and motor on...

Unless it is wood or plastic never place anything in the kerf behind the blade that the blade cannot cut. Screw drivers have been known to fall over when the kerf opens up and go to places they shouldn't.

[Mark e Kessler]

I suppose you are right, should have not suggested it on this forum. I have no issues with it though and works well plus it has a built in handle!


Unless it is wood or plastic never place anything in the kerf behind the blade that the blade cannot cut. Screw drivers have been known to fall over when the kerf opens up and go to places they shouldn't.