Ripping on Table Saw

[Justin Revard]

I am having trouble ripping boards on my hybrid table saw. It is apparent that as I rip my boards they are compressing onto my riving knife preventing safe progression of the cut through the blade. First this happened with reclaimed lumber (pine?) and I was not surprised, so I quit doing that. Now it has happened with my first hardwood (called blood something or other) as well. Grain on hardwood looked straight to me. First two cuts went fine, third cut could not be completed. The bend in the board causing the pinch is noticeable after the cut. How can I prevent this from happening?

Note: I have basically zero experience and have learned all I know on the internet and YouTube. Nobody mentions this problem that I’ve found. Fence looks quite square to the blade. I use a featherboard pushing workpiece gently against the fence just before the blade. The force that would be required to push the piece through the cut is scary and likely very dangerous.


Table Saw: Grizzly G0833P
Blade: Relatively new 24T Diablo (I will be investing in a good blade when I can).

Thanks for reading long post.

[johnny means]

Are you using a thin kerf blade?

[Justin Revard]

No it is a regular 1/8” kerf

[Bob Jones 5443]

It sounds like the face (or edge) of the board you are running against the table saw fence is not flat. Boards must be flat and square on at least two sides for safe ripping: the fence side and the side down on the saw table. This is where most folks use a jointer, but many also use a long hand plane to achieve flat and square.

If the fence face is not square, the board can move side-to-side during the rip cut, causing binding or worse (kickback).

By the way, it is also helpful to make the third side (a face) parallel to the other face before running through the table saw. For this you use either a planer (thicknesser) or a hand plane –– which requires a careful set of steps with a marking gauge and the plane.

[Mark e Kessler]

Sounds like tension in the wood, pretty common if thats the case you can talk a wedge in the kerf to open up but being new you probably wouldn’t feel safe doing that. Maybe your riving knife is too thick. No real way to prevent it and sometimes a completely clean looking board will do it. Is your fence toed out 1-2 thou, that can help

[Justin Revard]

Board is flat and square near as I can tell. Don’t construction workers rip out-of-square boards all the time on cheap table saws? I’m sure it is usually pine but I am very surprised how much trouble I am having. Perhaps no trouble if they’re not using a riving knife. I can test the fence for square to the table this evening, I checked this when I set the fence up. I have a small Porter Cable jointer I need to use for the first time, so I will try that too. Of course on YouTube they never have problems. :)

[Justin Revard]

I tried to toe the fence out a 1/64th but I’m not positive how good of a job I did. I need a machinist dial indicator. I considered the wedge option on the long reclaimed lumber but thought better of it for safety. My hardwood is for a cutting board and the piece does not make it through the riving knife for wedge to be an option.

[Ron Selzer]

"Don’t construction workers rip out-of-square boards all the time on cheap table saws"
This gets done by marking a straight line on the boar and free han feeding the board, not the safest way to work and nee lots of practice.
Take a string from one corner to the other of the board, is it exactly on the edge or hanging over or showing a gap?
Another way is to stand the board on edge on your workbench (shop floor if nothing else) and see if it rocks or shows light under the middle of the board.
Good luck
Ron

[Justin Revard]

Planer same as jointer, I have one and need to use it for the first time as well. It’s the dewalt that ‘everyone’ has.

[Orlando Gonzalez]

I have the same saw as you do and have not experienced this even with the stock riving knife. As others have said make sure the board has one edge trued and one face flat. I always start on the jointer truing up one edge and one face the to the planer to finish the other face. After this I go to the TS and rip the board(s) to width. I also have the Shark Guard riving knife and blade guard for it and it works well. You can also move the toe of the fence out around 1/64" to prevent pinching if it continues to be an issue. Another thing I did was to remove the stock fence face and install the Uni-T Fence you can get at Peachtree. https://www.ptreeusa.com/tablesaw_unifence.html It made a world of a difference for me.

[jamil mehdi]

You may need to tune your fence. It may be slightly pigeon-toed toward the back of the blade. That's the easiest solution. If the fence is square to the blade (or slightly toed out like Mark mentioned) you can easily adjust the position of your riving knife. There are four adjustment screws, two to set the left/right orientation, and two that adjust the plumb. It might be the plumb adjustment screws, so the riving knife looks fine where you take your measurements, but it's out above or below that.

My guess is the fence or the fence rail is out. A square fence at one distance from the blade won't be square from another distance if the rail isn't straight. These are the kind of things you deal with when you get a Grizzly. (Speaking from experience, not being preachy).

[Justin Revard]

I did not know about the riving knife adjustments. I will need to look into that. It is clear I need a dial indicator for sure.

[Justin Revard]

I will square my lumber from now on, I can’t take many risks being so ‘green ’. Thanks for the link, I have considered upgrading the fence. Would the blade quality make much difference?

[Jack Lilley]

If your ripping hardwood and its pinching the riving knife it is most likely not dried properly, case hardened. Sometimes it may be possible to get 1 or 2 rips off a board before it becomes a problem.

[Jim Allen]

I had that same problem ripping 2" thick myrtle wood, I solved it by cutting it in 2 passes, flipping it for the second pass.

[David Stone (CT)]

The short answer is, you can't prevent the distortion in the material if the material wants to distort, but you can switch methods to avoid the consequences. And 100% absolutely do not attempt to force a board that has bound up through the table saw. To do so would be to court a kickback. Stop feeding and turn off the saw immediately while retaining control of the workpiece. Once the saw is safely stopped, proceed to Plan B.

While not a good thing, having the kerf close up and bind the riving knife--or much worse, the blade--is a situation most every woodworking has, or will, encounter at least occasionally and understanding what's going on and how to deal with it is very important. As noted by others, there can be various causes but the most common is that solid wood isn't a 100% uniform material and boards sometimes contain internal stresses that cause the kerf to close up, or, alternatively, splay out like a Y, and the workpiece to bow or twist a little, as the board is cut or machined. Some species are more apt to act up than others, and construction lumber, which is grown fast and dried not so carefully, is especially prone. It's definitely unusual that you've had this experience twice in a row, but stranger things have happened.

In terms of Plan B, there are a few options. The best/easiest is to switch to the bandsaw and use that instead, to make rough rips, which you would subsequently clean up with a pass to the final width on the table saw. If you don't have a bandsaw, you could use a jig saw to accomplish the same thing--it will be slower, but the principle is the same: even in ill-behaved stock, the comparatively narrow band saw/jig saw blade won't generally bind up and even if the kerf closes up, the stock will not kick back, which is the danger of things with circular blades like the table saw. Another option is to stick with the table saw but only after inserting a small strip of wood that's the same width as the blade, or a hair wider, to force the kerf back open and eliminate the binding. My advice is that you eschew this last option, however, until you get a little more experience, since it involves starting up the saw with the stock already in contact with the blade.

Bottom line: This is a step on everyone's woodworking journey--and doing = learning.

[Bill Dufour]

The harbor freight 2" dial indicator, about $ 15.99, is plenty good enough for this job. Mount it with a wood screw in the lug to a 2x4 and clamp the 2x4 to the mitre guage to adjust the fence. make sure the plunger is pushed in a little bit when it is all mounted up. With a DI never rely on the needle starting at zero. always set the dial to zero. Otherwise it may not be touching and you can not tell, since the needle will not be moving.
Do not use a digital DI for this job!
Bil lD
Make something shaped like the rectangular object in the photo to mount you DI. I used a piece of 2x4

https://www.harborfreight.com/1-in-travel-machinists-dial-indicator-63521.html

[Lee Schierer]

The harbor freight 2" dial indicator, about $20, is plenty good enough for this job. Mount it with a wood screw in the lug to a 2x4 and clamp the 2x4 to the mitre guage to adjust the fence. make sure the plunger is pushed in a little bit when it is all mounted up. With a DI never rely on the needle starting at zero. always set the dial to zero. Otherwise it may not be touching and you can not tell, since the needle will not be moving.
Do not use a digital DI for this job!
Bil lD
Make something shaped like the rectangular object in the photo to mount you DI. I used a piece of 2x4

Although some of your ripping problem may be the material, if you haven't aligned your saw you need to stop everything and do that now. We would like to think that the saw would come aligned from the factory, but sadly that is often not the case. A dial indicator, even a $20 one will work very well for this job.

First you align the blade to the miter slot, either by moving the table top or if the blade is mounted to the underside of the table, by adjusting the trunnions. It helps if you can remove any side to side play of the miter gauge in the miter slot first. They make thin UHMW tapes that work very well for this.

Then you align the fence to the same miter slot again using the dial indicator. Some folks like to toe out their fence at the back, but it isn't necessary to do that. You certainly don't want it toeing in toward the blade. Many fence faces are not as flat as you would like so err toward having the fence leading away from the blade.

A well tuned saw will make your life much easier.

Lumber of any kind from the big box stores can be of questionable moisture content and will more than likely give you problems when ripping. Any lumber you bring to your shop should be allowed to acclimate for at least a week, preferably longer.

[Prashun Patel]

If you are having this problem with different boards I highly suspect it is your alignment and not the fault of the board.


Check first that your riving knife is the same thickness as your blade (or thinner) and that it is properly aligned. After this check your fence alignment.

Once you believe that is all proper , rip a plywood board. This will tell you if your alignment is good.

[Rick Potter]

My saw, riving knife and blade are all good, but this problem seems to show up more often in the last few years. As said before, case hardened hardwood, and lots of softwood with twisty knots.

Anyway, two things I do:

1: Shorten the fence if it adjusts, or add a short face that just goes to the start of the blade. This is for when the kerf widens rather than squeezes.

2: I keep some plastic wedges near to tap into the kerf when it squeezes the riving knife. The plastic will not damage the blade or be heavy enough to do damage if it shifts and pops back into the blade. The hardware store has wedges/shims that are the right thickness. Reusable also, mine have been used on the saw for a couple years.

[Jim Dwight]

A dial indicator is nice to have but you can align the fence with a combination square. All you do is to drop the edge of the movable face into the miter slot and move the scale to touch the blade at either the front or the back (I start with the front). Then slide the square to the other edge of the blade. The scale should touch with the same tightness of the other edge. If the back is tighter or too loose, you have to move the blade carriage. That process differs by saw, you need to consult your manual. After the blade is parallel to the miter slots, you need the rip fence to be parallel to the miter slots. The rip fence can be a little looser at the back. Carefully measure from the front and and back edges of the rip fence to the blade. The distance should be same or very slightly greater at the back.

I suspect your issue may be the riving knife is slightly closer to the rip fence than the blade. To check this, I lay a steel rule against the body of the blade with it extending out to the riving knife. If the riving knife is closer to the rip fence you will see that. If so, you need to move it away from the rip fence a little. Again, the process is in the owners manual (at least I hope it is). On my sawstop it has a little toothed piece that moves. On my previous saw, I used shims. One issue that saw manufacturers deal with is blade thickness. A riving knife that is OK with a standard kerf blade may be too close to the rip fence with a thin kerf. Mine is a little tight on my PCS but not closer than the blade, it is parallel with the teeth of a thin kerf blade. I am OK with that but it does increase the pinching if the wood warps a little and I have had to use a wedge before.

[michael langman]

A dial indicator is nice to have but you can align the fence with a combination square. All you do is to drop the edge of the movable face into the miter slot and move the scale to touch the blade at either the front or the back (I start with the front). Then slide the square to the other edge of the blade. The scale should touch with the same tightness of the other edge. If the back is tighter or too loose, you have to move the blade carriage. That process differs by saw, you need to consult your manual. After the blade is parallel to the miter slots, you need the rip fence to be parallel to the miter slots. The rip fence can be a little looser at the back. Carefully measure from the front and and back edges of the rip fence to the blade. The distance should be same or very slightly greater at the back.

I suspect your issue may be the riving knife is slightly closer to the rip fence than the blade. To check this, I lay a steel rule against the body of the blade with it extending out to the riving knife. If the riving knife is closer to the rip fence you will see that. If so, you need to move it away from the rip fence a little. Again, the process is in the owners manual (at least I hope it is). On my sawstop it has a little toothed piece that moves. On my previous saw, I used shims. One issue that saw manufacturers deal with is blade thickness. A riving knife that is OK with a standard kerf blade may be too close to the rip fence with a thin kerf. Mine is a little tight on my PCS but not closer than the blade, it is parallel with the teeth of a thin kerf blade. I am OK with that but it does increase the pinching if the wood warps a little and I have had to use a wedge before.


This is how I align the fence to the blade when ripping, but I always set the end of the fence nearest me to the correct length of cut I want. Then I set the square in the table slot at the other end of the table saw slot and tap the fence up to the edge of my adjustable squares ruler.
I have an older 15" craftsman adjustable square that gives me a god range of adjustment.

[Curt Harms]

For sure the blade needs to be parallel to the miter slot and the fence needs to be parallel to the blade/miter slot. I use the left miter slot because that's where I use miter gauges and jigs most of the time. You can set the outfeed end of the fence to toe out a little but don't use the fence on the other side of the blade if you do that, the fence would pinch the work as you cut. A benefit of having the fence exactly parallel is that you can use the fence on either side of the blade. I guess that matters more on a right tilt saw cutting bevels. My second thought would be to try a piece of decent quality plywood. Solid wood can move when cut, I've never had decent plywood move much at all. Decent plywood does not mean crappy CDX.

[Mike Kees]

After reading this far there are not many stones left unturned. My bet is that your Diablo blade is a thin kerf,and your riving knife is sized for regular thickness blades. Check that first. Then I would Adjust the saw ,blade parallel to miter slots,fence parallel to miter slots,riving knife in line with blade. Also take the time to set the blade stops at 90 and 45 degrees. This is step one with a new or new to you saw.

[Osvaldo Cristo]

I did not know about the riving knife adjustments. I will need to look into that. It is clear I need a dial indicator for sure.

Perhaps those videos can help to tune up and setup your TS:

Part 1: https://youtu.be/lxRSarTJLMU
Part 2: https://youtu.be/eikAX0pDKX4

Enjoy!

[Tom Bender]

If you are using a scary amount of force, stop! Always think about the direction of the force your hands are applying. Consider what would happen if the wood suddenly disappeared. It can happen in the blink of an eye.

[Curt Harms]

I did not know about the riving knife adjustments. I will need to look into that. It is clear I need a dial indicator for sure.

A dial indicator will work for sure but there are alternatives. I didn't have a dial indicator when I got my Griz 1023 so used a board with a screw in the end clamped to a miter gauge. The miter gauge fit the slot snugly, no slop. Used a feeler gauge to check the clearance between the screw head and a blade tooth. Be sure to use the same tooth or spot front and back.

[Bill Yacey]

Exactly. First thing I would check before anything else is the fence alignment. I don't use a riving knife myself, but if you do, it's got to be set square and centered to the blade.

[Lee Schierer]

A dial indicator will work for sure but there are alternatives. I didn't have a dial indicator when I got my Griz 1023 so used a board with a screw in the end clamped to a miter gauge. The miter gauge fit the slot snugly, no slop. Used a feeler gauge to check the clearance between the screw head and a blade tooth. Be sure to use the same tooth or spot front and back.

The problem with using a tooth is many of them are ground at an angle on the sides so getting the same point of reference is difficult the flat of the blade is a more consistent point of reference. I simply put a dot on the blade flat area with a sharpie.

[Gordon Dale]

This thread exemplifies Sawmill Creek at it's best--thoughtful, detailed, non-judgmental answers to a common and potentially dangerous issue encountered by woodworkers at all levels. I'd like to thank everyone who contributed.

[Alex Zeller]

The first thing I would do is look at the cut in the board you just made. If it looks like the gap is narrower at the end of the board than where you stopped cutting then it's the wood. Another simple check would be to get a straight edge and place it against two teeth on the blade extending past the riving knife. Do it on both sides of the blade. The straight edge shouldn't touch the riving knife. Instead it should have an equal gap. Make sure to do it the full length of the riving knife (while not as bad as a splitter) you want to check that it's not twisted compared to the blade. That being said I do agree with the others about calibrating the saw. When you do don't forget to do it with the blade at both 90 and 45 degrees.