Edge joining: Air gaps after jointing - Woodworking Talk - Woodworkers Forum

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post #1 of 20 Old 02-13-2017, 11:52 PM Thread Starter
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Edge joining: Air gaps after jointing

I am working to edge join some walnut for drawer fronts and after jointing am seeing a small air gap between several of the boards. I am a bit concerned about having a bad glue seam if I glue up without fixing it.

The boards seem perfectly smooth and flat, and I haven't had trouble with any of the other pieces, but after re jointing still having issues with these.

I don't own a jointer so my process is to rip to width on the table saw then edge joint on my router table. This has worked fine in the past including on this project.

Any ideas what is going wrong, and what I can do to fix it?
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post #2 of 20 Old 02-14-2017, 04:14 AM
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You've got problems somewhere in your jointer setup is my guess. I'm going to go with the tables/fences not being co-planer. If the other pieces are shorter, I'd be willing to wager that they have the same issue, it's just not as noticeable, being that the bow of the edge will increase as the length does

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post #3 of 20 Old 02-14-2017, 07:11 AM
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Quote:
Originally Posted by Peter StJohn View Post
I am working to edge join some walnut for drawer fronts and after jointing am seeing a small air gap between several of the boards. I am a bit concerned about having a bad glue seam if I glue up without fixing it.

The boards seem perfectly smooth and flat, and I haven't had trouble with any of the other pieces, but after re jointing still having issues with these.

I don't own a jointer so my process is to rip to width on the table saw then edge joint on my router table. This has worked fine in the past including on this project.

Any ideas what is going wrong, and what I can do to fix it?
I'm guessing you are using a router for a jointer. If your jointer fence isn't completely straight it can cause the board not to pass straight across it. It would be like a real jointer with the rear table too high. The problem could also be dust. If dust is getting between the board and the fence that could cause it. You could also be putting too much pressure at the middle of the board and not enough on the ends.

From where you are try starting the cut at the middle of the board and run it to the end and then turn the board around and start at the middle again. See if that straightens it.
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post #4 of 20 Old 02-14-2017, 08:09 AM
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Router tabvle jointing issues

You said:
I don't own a jointer so my process is to rip to width on the table saw then edge joint on my router table. This has worked fine in the past including on this project.

Epic said:
You've got problems somewhere in your jointer setup is my guess. I'm going to go with the tables/fences not being co-planer.

Steve said:
I'm guessing you are using a router for a jointer. If your jointer fence isn't completely straight it can cause the board not to pass straight across it.

To use a router table for jointing, requires a 2 piece fence where the front fence is off set inward from the back fence. This allows the cutter to remove material from the infeed edge and then that edge rest/registers on the rear fence. The off set should be about 1/16" or so.


In my opinion, this set up works best with shorter pieces and will not work well with pieces longer than 3 ft or so. I would use either of two methods at this point. You can mate each pair of pieces to one another by using a hand plane and checking the gap as you proceed. The question become which piece gets the planing, but trial and error will tell you that.

The other way is to use a reference straight edge to determine where to remove the material. Use chalk, carpenter's marking crayon or Crayola on the straight edge and rub it against the work to see where the marks are left. These are the high spots which need your planing.

Jointing on a regular jointer, requires a precision setup and usually a cup or hollow on the edge means your rear table is too low. All the typical jointer issues are addressed here:
http://newwoodworker.com/jntrprobfxs.html
Quote from the link above:
Though less likely, the same thing can occur with a long board that already has a concave shape in the surface being jointed. If the board is too long, the ends are never on the tables at the same time and the concave shape can remain or even be made worse. If possible, cut the board to a length closer to what is actually needed for the project. You can also reverse shorter boards to help take equal amounts from both ends until it is flatter on the jointer beds. Then take all remaining cuts with the grain.

The answer to your question will only be as detailed and specific as the question is detailed and specfic. Good questions also include a sketch or a photo

Last edited by woodnthings; 02-14-2017 at 09:35 AM.
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post #5 of 20 Old 02-14-2017, 02:48 PM Thread Starter
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Looking at my boards more closely it does look like they are matching at the ends, then getting the air gap near the middle, which tells me they have a slight curve.

They are the same length as everything else I jointed (about 12x 45" boards) and the only two that have an issue so I am thinking maybe they started with a slight cup and I reinforced is as they are on the long side for jointing on a router table.

I will try starting from the middle and working out to the two edges to see if it fixes the issue. If not it may be time to go buy a hand plane, it's been on the list for a while anyway.

I can also take them back into the community shop I did the original milling on and joint them on a big jointer, but that costs money and I was hoping I was done with that part.

I am assuming gluing them like this with a lot of clamp pressure is a bad idea.
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post #6 of 20 Old 02-14-2017, 04:40 PM
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Quote:
Originally Posted by Peter StJohn View Post
I am assuming gluing them like this with a lot of clamp pressure is a bad idea.
Yes.
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post #7 of 20 Old 02-14-2017, 05:13 PM
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Quote:
Originally Posted by Peter StJohn View Post
Looking at my boards more closely it does look like they are matching at the ends, then getting the air gap near the middle, which tells me they have a slight curve.

They are the same length as everything else I jointed (about 12x 45" boards) and the only two that have an issue so I am thinking maybe they started with a slight cup and I reinforced is as they are on the long side for jointing on a router table.

I will try starting from the middle and working out to the two edges to see if it fixes the issue. If not it may be time to go buy a hand plane, it's been on the list for a while anyway.

I can also take them back into the community shop I did the original milling on and joint them on a big jointer, but that costs money and I was hoping I was done with that part.

I am assuming gluing them like this with a lot of clamp pressure is a bad idea.
Using a lot of clamp pressure has been done a lot it always has an unhappy ending. First if you get into the habit of using a lot of pressure you will end up bending the clamps. Then the ends of the board where the joint meets fine you will end up squeezing out too much glue which weakens the joint at the end. Then the amount of pressure you use to force the boards together will be how much pressure there will be trying to pull the joint apart. In the long run you would be so much better off making the parts fit well.
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post #8 of 20 Old 02-14-2017, 05:23 PM
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I use a sure fire no-can fail method on the table saw.

first, you have to have oversized pieces.
put the two boards together, gaps and all, tack nail a cleat xgrain on the top at each end.

raise the table saw blade so it cuts the thickness of your board, but does not cut through the cleats.
then align the joint, gaps and all, with the saw and rip down the joint line.

presuming the gaps are less than the saw blade kerf, you get an absolute perfect match first time.
if the bow/gaps is too much, remove cleats, push boards together, re-cleat and re-rip.

glue those two perfect match edges together, dry, then proceed to the next (wider) board.

the obvious 'trick' here is that the saw blade/kerf cuts both sides parallel and plumb, or not...., in the same pass = identical mirror edges to join/glue.

joiners are nice, routers sorta' workable for the situation, but 'dead nuts easy' is really neat.....
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post #9 of 20 Old 02-14-2017, 05:58 PM
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nice tip

The only issue is that the joint to be cut must be parallel to the fence OR a second piece must be scabbed on to make it so. You can't cut the kerf freehand, you must use the fence for safety concerns. The same plan can be used with a circular saw and a straight edge if you don't have a table saw OR the pieces are long and heavy.

The answer to your question will only be as detailed and specific as the question is detailed and specfic. Good questions also include a sketch or a photo
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post #10 of 20 Old 02-14-2017, 05:59 PM Thread Starter
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Quote:
Originally Posted by MT Stringer View Post
Yes.
Sometimes you need someone to tell you even though you already know the answer.
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post #11 of 20 Old 02-14-2017, 06:05 PM Thread Starter
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Never heard of this. I will have to try it out.

The gap at this point is probably only 1/32"
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post #12 of 20 Old 02-14-2017, 07:17 PM
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That's acceptable!

Quote:
Originally Posted by Peter StJohn View Post
Never heard of this. I will have to try it out.

The gap at this point is probably only 1/32"
That 1/32" gap is OK. Sometimes woodworkers use a "spring" joint which is a curved gap between the two boards:
http://tommymac.us/2014/08/spring-joints/

Your clamps will not not be over stressed for this amount of gap. Use cauls on top and bottom to keep the boards aligned. Slightly curved cauls put pressure downward forcing the boards flat. However, straight cauls are better than no cauls ... just sayin'
Do not over clamp the boards as the rhat will cause a "staved" glue joint, which is weaker.

The answer to your question will only be as detailed and specific as the question is detailed and specfic. Good questions also include a sketch or a photo
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post #13 of 20 Old 02-17-2017, 09:13 AM
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I just use the jointer to get a straight edge, then rip to size on the ts, and glue up. Is this wrong?
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post #14 of 20 Old 02-17-2017, 09:27 AM
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I just use the jointer to get a straight edge, then rip to size on the ts, and glue up. Is this wrong?
That's alright to joint and rip the wood but it would be better if you came back and jointed the sawn edge. The texture of the saw cut will hold the wood apart making the glue line a little thicker than it should.
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post #15 of 20 Old 02-17-2017, 12:34 PM
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Quote:
Originally Posted by Pirate View Post
I just use the jointer to get a straight edge, then rip to size on the ts, and glue up. Is this wrong?
Depends on your blade.

“Everything we hear is an opinion, not a fact. Everything we see is a perspective, not the truth.”
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post #16 of 20 Old 02-17-2017, 12:57 PM
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I get a very smooth cut on the TS

Quote:
Originally Posted by Steve Neul View Post
That's alright to joint and rip the wood but it would be better if you came back and jointed the sawn edge. The texture of the saw cut will hold the wood apart making the glue line a little thicker than it should.
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Depends on your blade.
My jointer leaves little scallops unless I feed it very slowly with a light pass. The limitation of jointers is their table length. Unless you have a "aircaft carrier" jointer it will be difficult to get straight edges on long boards because they will tip off the far end of the table... unless you have them properly supported. I find it much easier and faster to edge joint boards under 8 ft using a straight line rip jig on my table saw. The first cut is the final one, no additional passes are required, unlike the jointer. No worries about snipe either:



This went as fast as I could clamp and unclamp the boards, rip them and stack them.

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post #17 of 20 Old 02-17-2017, 01:34 PM
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I get a few scallops with my northfield jointer but I think that is due to the previous owner not having the knives set right. My little craftsman makes cuts which look more like it was done with a hand plane. I look forward to the day when I can get that jointer to a permanent location where I will probably sharpen and set the knives to where it cuts as well as the craftsman.

As far as the table length on the craftsman, I built an extension behind the rear table which enables me to joint lumber up to about 10'.

I worked for someone else onetime that used a glueline rip blade. It did a better job of ripping a smooth edge but the guy was having cabinet doors come back because some of the panels were coming unglued. For this reason if at all possible I feel it's better to dress the wood to be glued.
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post #18 of 20 Old 02-17-2017, 03:14 PM
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Quote:
Originally Posted by woodnthings View Post
My jointer leaves little scallops unless I feed it very slowly with a light pass. The limitation of jointers is their table length. Unless you have a "aircaft carrier" jointer it will be difficult to get straight edges on long boards because they will tip off the far end of the table... unless you have them properly supported. I find it much easier and faster to edge joint boards under 8 ft using a straight line rip jig on my table saw. The first cut is the final one, no additional passes are required, unlike the jointer. No worries about snipe either:



This went as fast as I could clamp and unclamp the boards, rip them and stack them.
Looks just like mine. The only difference is mine is shorter. With space limitations, I usually try to pre determine my cuts and cross cut the material if at all possible. Then one pass through with this jig and it's on to the next board. Just like Woodn' said. It works great.
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post #19 of 20 Old 02-17-2017, 03:56 PM
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I made two of them

I made an 8ft and a 5 ft jig and had a Dubby Taber jig which will do 3ft so I have it pretty much covered!
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post #20 of 20 Old 02-20-2017, 08:59 PM Thread Starter
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RESULT:

I sanded down the edges to try and reduce the curve a bit (I know a plane would be better but I don't own one), then ran them through my router table (used as jointer) again.

They still had a very slight curve making a tiny gap when when set up for gluing. I read a bit about spring joints, and tested by using a trigger clamp to squeeze the gap closed. A single clamp across the middle was pulling the boards tight together all the way across with minimal pressure so I felt good to go.

Turned out to be the cleanest glue up in the project so far. Thanks guys.
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