bgreenb

trouble edge jointing long boards for table top

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I am building a dining room table with a fairly large top (40" x 80").  I've milled the boards completely flat, but I've become VERY frustrated trying to edge joint them.  I've gone over my jointer setup several times and it is dead on.  I know the right techniques in theory, but maybe I'm not executing them correctly.  I'm using a featherboard to keep the board registered against the fence so I can use both hands to apply pressure correctly, and I'm using outfeed support to make sure the board doesn't tip up as more of it exits the outfeed table.

 

But I'm ending up with a slight concavity in each edge (around 1/32") every time. 

 

I've heard of sprung joints - can I just clamp out that 1/32"?  Will it lead to problems over time?  I just don't have it in me to keep trying to re-joint these long boards.  I've redone each board at least 4-5 times.  At this point I'm not sure what to do.  Any help would be greatly appreciated.

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I don't have any experience with 'sprung joints' but it seems to me that if each board has the same concavity on both sides, it would accumulate and be pretty hard to compensate across a 40" table (e.g. 4 boards would have 6 glued edges, or 6/32" total to close up).

 

I think a concave edge is the result of one of the tables outer edges dropping, so that as the board goes over the cutter it scoops more out of the middle.  Do you have a straightedge long enough to check the tables end-to-end?

 

If you can't nail it with the jointer, you could try a straightedge clamped to the boards and use a router with a pattern bit to get a nice straight edge.

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I am wondering if you are putting too much downward pressure on the boards.  Seems your jointer should be long enough to joint those boards without the outfeed support.  As PB indicated, I would try a couple passes without it, and let the weight of the board do most of the work for you.

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It's a big jointer - a Grizzly 8" with a 72" bed.

 

So basically the max capacity is about 35" meaning that for every fraction of an inch your off with your bed your going to be off about 4 times that on your 80" board.

Get rid of the supports your never going to get them close enough. Go to home depot and buy yourself 2 8ft 2x6's. Joint off the rounded over edge and mark the face of each board. Joint each one, one with the face mark against the fence and the other with it away from the fence. You should be doing this with all your edge jointing that is going to be glued up anyways. If you have a gap at the center of your 2x6's raise your out feed. Use a set of feeler gauges between the stops or between the table and the fence. Raise it about 6 thousandths at a time and recheck the joint. Keep doing this until your joint on the full 8ft board is dead on. Now your jointer is adjusted properly. 

 

Your never going to get a jointer adjusted perfectly with a straight edge and feeler gauges. So on long boards every tid bit your off is amplified. 

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Thanks guys, I will try all of this.  It could be the downward pressure, I will try jointing a board without it.  They are heavy boards, so you're right that the weight should be enough.  I will also get rid of the outfeed support.

 

I will also try the 2x6 adjustment method.  I actually have a few long 2x6's in my shop, so I will give that a shot. 

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The boards range from a couple of narrower boards (~4.5") to a couple of wider boards (~8").  The widest board is 9". 

 

Thanks higtron - if I can't get this to work then I might try that method, but ideally I'd like to be able to use the jointer for this task since that's what I bought it for :)

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I have a 6" jointer, and I also have trouble jointing long boards. So I make a straight edge jig for my table saw like this one

tsjntjiglead305x400.jpg

It's quick, and easy with a good blade 90 Deg. to the table you have glue ready joints in no time.

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==> Go to home depot and buy yourself 2 8ft 2x6's. Joint off the rounded over edge and mark the face of each board. Joint each one, one with the face mark against the fence and the other with it away from the fence.

 

==> You should be doing this with all your edge jointing that is going to be glued up anyways. If you have a gap at the center of your 2x6's raise your out feed. Use a set of feeler gauges between the stops or between

==> the table and the fence. Raise it about 6 thousandths at a time and recheck the joint. Keep doing this until your joint on the full 8ft board is dead on. Now your jointer is adjusted properly. 

==> Your never going to get a jointer adjusted perfectly with a straight edge and feeler gauges. So on long boards every tid bit your off is amplified. 

 

Interesting advice.  You know, I do something like that, but more out of habit rather than intent...

 

I use the feeler-gauge/straight edge method to 'get close', then i always joint some long stock to dial-it-in.  it's sort like tablesaw jigs -- I get close with an engineering square, but use the 5-cut-method to dial-it-in...  I've never actually thought of it, but just 'do it' out of habit.

 

This is one of the things I'd add to a FAQ if Marc decides to add a section for FAQs/tips/etc.

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The boards range from a couple of narrower boards (~4.5") to a couple of wider boards (~8").  The widest board is 9". 

 

Thanks higtron - if I can't get this to work then I might try that method, but ideally I'd like to be able to use the jointer for this task since that's what I bought it for :)

 

If your having the same issue with boards from 4 1/2" to 9" wide and are not a gorilla, pressure is not your issue. No way your flexing a 9" wide board on edge taking the bow out with hand pressure. On the other hand if you are a gorilla we need a video. :)

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I am not a gorilla, in spite of what my wife thinks :)

 

The issue is definitely worse with the narrower boards, but it exists on all of them.  So maybe I'll focus on setup first with the 2x4's like you said, but I'll also keep technique in mind.

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I wish!  The only hand planes I have are a block plane and a shoulder plane for trimming tenons.  Someday I'll expand that collection.

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