Why is this happening? Saw, jointer, stock?

[Philip Berman]

I'm attempting to rip 1 1/2"-wide stiles from a larger board(walnut), approx. 70" long. As you can see from the photo, as I rip, the back end is closing up and the further I go through the length of the board the more difficult it becomes to continue pushing through the saw. I get to a point where it's either impossible to push or I become too wary of continuing and turn off the saw. I then have to wrestle the board to get it out of the kerf. I do have a splitter, which I guess is a good thing. I previously had thought that this was a problem, that it was out of alignment, so I made a new insert, checked the fence for parallel, made a new jig to drill for the insert, and then did so. This only happens with long-ish boards. I just previously ripped several dozen boards, same width, same lumber, same saw, same everything except they were only 28" long. I have just re-adjusted everything on the saw in anticipation of this project. This has been a problem from day one with the saw, many years ago, and I've always chalked it up to operator error, but after all this time I'm doubting that is the case. It's also happened, only on long boards, in maple, oak and now walnut. One thing I suspect, due to the fact that it only happens with long pieces of stock, that I'm exceeding the ability of the jointer to make a straight edge over such a distance. But it seems to me that I would still be able to saw a parallel edge, it just wouldn't be straight. I have a Hammer A3-31 which has a 24" infeed and a 24" outfeed, for a total table length of 48". However, I previously had a Jet 6" jointer and had the same issues (I think the Jet had longer tables). Also, I don't see how that would be causing the kerf to close up the way it is as shown in the attached picture. Anyone have any ideas?

Philip

[Ben Hatcher]

Generally, the kerf closing is due to internal stresses in the wood. When you say this happens with long stock, is it with long stock from this current batch, or any long stock? I suspect that it is the wood, not the saw.

[Jamie Buxton]

Like Ben says, internal stresses in the wood. The fix is to rip the stiles a little wide, then restraighten one edge on your jointer, then re-rip. On the re-rip, you're taking off only a smidge, so the stile should not bend any more.

[Andrew Pitonyak]

A few thoughts

The points of interest for me it that this always happens, which implies to me that it is not related to internal stress or sometimes it will happen and sometimes not. It has happened since day one...

That leads me to expect that either the blade is not properly aligned, or the fence is not properly aligned.

On the other hand, you did say that it was difficult to pull the wood from the blade. I assume that this is after you have moved the fence so that you know for certain that the fence was not pinching the blade against wood.If this is the case, well, I would not really expect an alignment issue to be the problem.

Have you tried a feather board holding the wood against the fence before the wood enters the blade. This will keep the board tight against the fence so that you are less likely to send the wood in at a slight angle?

Does this occur if you do not use the rip fence? I am not sure how to test this without a sled, but I don't expect that you will not have a sled of the correct size. Perhaps attaching to a known straight edge and sending it through.

Is the board properly jointed along one edge so that the wood itself is not changing dimensions and pushing the wood into the blade?

Are you using a rip blade? How thick? Is it possible that the blade itself is flexing? That feels like a long shot. Well, they all feel like long shots.

[David Nelson1]

That happens to me as well, not as often as what you are describing. I use a wedge made from a small cut off when it gets to be a problem, of course you will have to stop and insert it. I have a tall splitter with anti kick back pawls with a gaurd, (stock C man part) the point is it's longer than the drop in splitter your using.

[Ben Hatcher]

In the photo, the kerf is closed and the board is just sitting on the saw. I can't think of anything other than internal stresses in the wood that would cause this. Fence alignment might cause binding while cutting, but wouldn't cause the kerf to close after the cut. If the saw is strong enough, and presuming you're using a carbide tipped blade where the tips are wider than the blade, a misaligned fence would simply cause chips to fly up from the back of the saw as the fence pushes the material into it.

[J.R. Rutter]

Generally, the kerf closing is due to internal stresses in the wood.


Like Ben says, internal stresses in the wood. The fix is to rip the stiles a little wide, then restraighten one edge on your jointer, then re-rip. On the re-rip, you're taking off only a smidge, so the stile should not bend any more.


I can't think of anything other than internal stresses in the wood that would cause this.

4th. You will get burned at least half the time trying to rip long parts exactly to width.

[Prashun Patel]

His problem, however, is that he can't even complete the cut - even if he did make the rip a little wider.

To remedy this I've done two things in the past:

1) Rip 75% of the way thru on the initial pass, then flip and rip the rest. You'll more than likely have a ridge to remove after, but if you rip a little wider than necessary, this is moot. This also requires yr pieces have roughly parallel faces.

2) DANGEROUS: If you're already stuck and are having a devil of a time getting the piece out, and really really want to complete the cut, then turn off the saw, and use a wedge in the completed part of the kerf to draw the pieces apart a smidge. If I'm able to pull the piece out, I will and then use method 1. But I have also lowered the blade, restarted the saw, and then raised the blade into the piece, and completed the cut.

3) You can also rough rip yr boards on the bandsaw first.

[Johnnyy Johnson]

I had that happen once before. I had bought some Walnut from a kiln and found out later that it had been dryed on the same schlude as Poplur.

[Bill Huber]

I am in no way a table saw expert but there is no way a saw could be out of line and cause the kerf to close, it has to be the wood. If the fence was out of line then you could get binding but the kerf would not close.
Rip it on the band saw and I will bet you get the same thing.
If you want to do a test get some 3/4" plywood and rip off an inch or two and I bet the kerf does not close.

[Dave Zellers]

2) DANGEROUS: If you're already stuck and are having a devil of a time getting the piece out, and really really want to complete the cut, then turn off the saw, and use a wedge in the completed part of the kerf to draw the pieces apart a smidge.

I've done this many times. Sometimes the tension is so great, the board explodes apart with about 2" left to rip.

Gets your heart going... :eek:;)

[Greg Portland]

I am in no way a table saw expert but there is no way a saw could be out of line and cause the kerf to close, it has to be the wood. If the fence was out of line then you could get binding but the kerf would not close.
Rip it on the band saw and I will bet you get the same thing.
If you want to do a test get some 3/4" plywood and rip off an inch or two and I bet the kerf does not close.Bill, some bandsaw blades have a good deal of set which makes them better for ripping problematic wood (back of blade is narrower than the cut width). Plus, the total amount of the blade in the cut is ~3/4"-1" versus 6"-8" for a TS blade. For these reasons I'll use a bandsaw to rip problematic wood.

[Rod Sheridan]

As others have noted, it's internal stress in the wood.

Bandsaw time...............Rod.

[Bill Huber]

Bill, some bandsaw blades have a good deal of set which makes them better for ripping problematic wood (back of blade is narrower than the cut width). Plus, the total amount of the blade in the cut is ~3/4"-1" versus 6"-8" for a TS blade. For these reasons I'll use a bandsaw to rip problematic wood.

But no matter what the thickness of the blade is, if there is stress in the wood the kerf will still come together on a long board. I guess I should not have said the same thing, it may not bind but the kerf will still come together.

[Don Jarvie]

How long of a board does this begin, ex- over 40, 50 , 60 inches? Make some test pieces that are square and flat off the jointer and run them through the TS and see what happens, say in 10 inch increments. As you increase the length does the problem start at some point, ex 50 inches is ok but 60 it starts to happen?

The reason for the exercise is to eliminate the tools causing the problem, then your technique and finally the wood. It maybe a case of as the longer the boards get the harder it is to control them going across the jointer and through the saw.

[Prashun Patel]

I've had a bandsaw bind (less frequently) on a closed kerf too. The thing is, (assuming proper support) there's no risk of kickback, so you can turn off/on the saw and wedge it, or even push pull it to slightly widen the kerf when you notice it starting to tension or close; you just have more options making it a little easier to complete the cut.

On the downside, if it really gets stuck, it's really hard to get it off - especially if that piece is a 12" thick 40lb stump of turning blank (DAMHIKT)

[Philip Berman]

I've figured it out, and it's really kind of stupid (to have not thought of this sooner).

The project is a wall of bookcases flanking a fireplace mantel/overmantel. I've been very selective about the wood chosen for the faces that will show, and hence I've been culling out anything with a knot, swirl, grain-change, anything and everything other than straight even grain. On the upper section of the bookcases I don't have the luxury of being so picky due to the height (68"), and so I'm using wood that I otherwise would have discarded. Not that I'm using knots and all that stuff, but in order to maximize the yield there are some knots that will ultimately be hidden under moldings, sometimes a portion of a knot which will be on the backside of the stile, etc. THAT's why I'm having so much trouble with the long pieces. When I do get a perfectly straight-grained portion of the board that has no blemishes front and back, everything is fine with my jointing and sawing. In short, any kind of reaction wood is causing stress that's being relieved when I slice off relatively narrow pieces, causing them to bind.

There's a problem with binding on the bandsaw too, but not nearly as bad. What I've done is over-size the rip on the bandsaw, re-joint the previously jointed edge, then cut to actual width taking off a very small increment, maybe 1/4", with the tablesaw. Problem solved, straight stiles, no binding.

My statement about it always happening is true, and a close look at my benchtop (maple) leads one to the same explanation - I was sawing 1 1/2" strips of 8/4 maple which had swirls, quilting, you name it. Back then, it was the first thing I had ever built, and I thought it was normal to use all 190-lbs of me to push the wood through the saw, and to nearly break a wrist pulling everything tight with clamps when gluing up. I suppose without a spreader I may have been killed on the first project. All of my other projects have used considerably smaller lengths of lumber and were carefully culled for uniformity of grain, and therefore were much more stable.

[Todd Burch]

Where (rhetorical - I don't care where, because I won't know the place) are you buying your lumber? Are they a distributor or do they dry the lumber you are buying? I would vote for drying (improperly) induced internal stresses. Yes, knots will cause some movement, but THOSE KNOTS won't cause THAT movement on their own.

[Harold Burrell]

As others have noted, it's internal stress in the wood.

Bandsaw time...............Rod.

Bingo. I couldn't agree more.

[Sam Murdoch]

In the photo, the kerf is closed and the board is just sitting on the saw. I can't think of anything other than internal stresses in the wood that would cause this. Fence alignment might cause binding while cutting, but wouldn't cause the kerf to close after the cut. If the saw is strong enough, and presuming you're using a carbide tipped blade where the tips are wider than the blade, a misaligned fence would simply cause chips to fly up from the back of the saw as the fence pushes the material into it.


Agree with Ben and all others who attribute this to internal stress. And a big DITTO to Prashun's post - THIS IS DANGEROUS!
You should not be fighting your saw, nor holding on for dear life, nor pushing so hard that if everything releases you will fall forward, or pull back on your piece as the saw is running - and if you stop and start up the saw in a mid rip be aware that the board may bind and kick back. Keep your wits about you. Know what to expect. Know that you more than likely will not be able to counter the force of the saw safely.

When you are ripping such gnarly wood on a table saw you will know within a few inches to a foot that your lumber is binding. Stop the saw.
Lower the blade to be cutting only 1/3rd to 1/2 of the boards depth and then begin the shallow rip. So what if it takes 2 or 3 passes over the saw to rip your boards? SAFETY TRUMPS EFFICIENCY EVERY TIME! Oh, if you are not already - you should be using a carbide RIP blade.

The problems with adding a wedge to the end of your cut after it has gone past the saw blade are:
1) You must stop the saw then restart it in mid rip - dangerous - see above.
2) If there is that much internal stress in a board and you are forcing it to remain open you run the risk of having it explode open at the end of the rip. If you haven't experienced such a release - believe me - such action is likely to cause explosive release in more than just your lumber :eek:.

It is great to be able to use highly figured wood in your work, but please be careful Philip. Reading your first post made me very uncomfortable. You must know by now that we care :D.

Regards,

Sam

[James White]

If all or most of the material that does this comes from the same source. I would find a new source.

James

[Jeff Duncan]

Been there, done that....I use wedges also.

If your comfortable doing it I recommend just popping them in the saw cut once it's say a foot or so past the back of the blade. To me it's just safer that way as I don't like re-starting the saw with a piece mid-cut.....but I've been using table saws for a long time so I have a pretty good feel for what the wood is doing as I'm cutting. If your not comfortable popping them while sawing then maybe the bandsaw method would be better suited.

good luck,
JeffD

[Ron Natalie]

This is one of the times a helper comes in handy.

[Michael W. Clark]

Sounds like you found the problem. I use the bandsaw now too when I get problem wood. I just saw this post, but I would have suggested trying some 3/4" plywood to see if it closes also. If it closes, then it may be a setup issue, if not, then more than likely the internal stresses of the wood. I had this happen to me on some hard maple. As Jeff said, the saw definitely sounded different and I shut it off before anything happend (good reason for a knee kick). The board closed about 6-8" behind the blade, it was headed for a kickback.

[Chris Tsutsui]

Never had to do this myself but maybe you can cut about 3/8" on one side, then cut 3/8" on the other side. Then that leaves you with a 1/4" left in the middle of your board which prevents it from closing up.

Then you can finish cutting the board with your bandsaw or jig saw. You can then use a wedge to prevent the wood from closing up if it's pinching your jig saw blade.

Your Hammer A3-31 will mill the pieces well though I would cut the timbers oversize and let it adjust because that wood will probably move around a lot.

[michael case]

Cut oversize, rejoint cut a bit closer, rejoint and make final rip. I find most wood will not stay perfectly straight and some, like the new farm-raised mahogany, really crooks. Count on some over sizing and rejointing. Its slow and takes more wood initially, but lest wasteful and quicker than tossing stock out.

[Mike Cruz]

Philip (with one "l"...my middle name...we are a rare breed), my guess is that it is simply the wood. My recommendation is to rip the wood about 1/4" wider than needed, take it back to the jointer, straighten the concave edge, and then cut to width on the table saw again. Wood will move. That is a given. Sometimes it is subtle (with climate changes), other times it is in a scary/dangerous way (while on the saw). My rule of thumb with flat work is that if you NEED it straight and true, cut it larger than you need and recut it. Because when you don't, it WILL move on you...

[Larry Edgerton]

My statement about it always happening is true, and a close look at my benchtop (maple) leads one to the same explanation - I was sawing 1 1/2" strips of 8/4 maple which had swirls, quilting, you name it. Back then, it was the first thing I had ever built, and I thought it was normal to use all 190-lbs of me to push the wood through the saw, and to nearly break a wrist pulling everything tight with clamps when gluing up. I suppose without a spreader I may have been killed on the first project. All of my other projects have used considerably smaller lengths of lumber and were carefully culled for uniformity of grain, and therefore were much more stable.

If this is not an isolated incident you need to find a new place to buy wood. ONE THAT KNOWS HOW TO CUT AND DRY PROPERLY!

Larry