Thread: Anyone Used a Glue Joint Bit for Table Top Glue-ups?

TP1,
Got one of those things and have yet to use it on a project.
I did a couple of test runs with it and in the end decided I was better off with biscuits.
My experience was this:
They are a bugger of thing to set up as any error in setting the height is doubled in the final assembly.
Unless you have dead flat pieces to joint (I'm using a router table not free-hand router) then you will get a variation in cutting height.
Because the edge is continuous you are locked in for the entire length of the joint and you cannot make adjustments for small variations as you can with biscuits etc.

The theory is good - more surface area for glueing, good shear strength - but I'm not sure I would be using it for a big job such as yours without the means to tightly control the cutting height

Just my experience

Ian

Hi there TP1, i used to use them years ago as a woodmachinist, the advatages are that they do give an easy quick and strong joint, the downside to them though, is they aren't all that good when you are making a quality item like a flash dining table top. When you glue up the top you will see the joint on the ends, which detracts from the beauty of top like the one your making.

If i where you i would stick to the biscuits or domino's, as long as you place them close the ends and in close regular intervals along the length of the boards, you will still end up with a strong top. Hope this helps you.

Personally I wouldnt bother with any joint methods, just machine them nicely square and use cauls. A slight convex curve in the clamping face of the caul's goes a long way to help especially across the distance of a dining table.
Another possibility is to use it as an excuse to justify buying some panel clamps like compressX

Hmm, It seems I should stick to what works and not go down that path. I hadn't fully considered the centring/alignment issue or how it would detract from the look of the table. It would be very frustrating to go through the motions only to be disappointed . Thanks a heap guys.

I've used a CMT reverse glue joint router bit to join a couple of table tops, I was happy with the result.

I used a handheld router to do the glue joint cuts, I wouldnt try to do it over a router table. The resulting glue lines are barely visible on the ends because the two halves fit together perfectly. I liked the fact you just had to spread glue on both edges and then clamp it up, the profile takes care of alignment.

Just do a couple of test cuts first on some scrap which is the same thickness as the boards you are using before you start on your good boards, to get the router bit depth spot on.

I will use mine again when the need arises.

Ironwood,
That bit is not designed to be run in a hand held router

With a diameter of around 44mm you're living waaaay too dangerously

Ian

Personally I think it is a waste of time. Long grain to long grain forms a strong bond anyway. I doubt you can get anything stronger.

Originally Posted by Wongo

Personally I think it is a waste of time. Long grain to long grain forms a strong bond anyway. I doubt you can get anything stronger.

Ditto.

If anything, I would plane the slightest hollow along the edges (only just visible with the two edges together) and then glue them and clamp them lightly. Beat them where necessary with a dead-blow on a piece of scrap to level the joints and then snug the clamps up tight.

These are used not only to align and lock the edges of the boards together but more importantly to increase the glue surface area ( almost double ) to that of a butt edge. Having said that using a router cutter to perform this task on Jarrah is not ideal it should be done with a profile block on a spindle moulder.
Cheers Bazz

Harry72 hit it on the head.
Clamps & cauls & a good square edge & theres often no need for biscuits or dominos. For most joins an edge from the jointer is sufficiant for a good glue face. When gluing up jointer edged boards i alternate the board face against the fence so that any slight error in square that may be in the jointer fence is canceled out in the oppersite edge. On longer boards i use a straight bit in a router & a good quality straight edge.

Originally Posted by Ian Smith

Ironwood,
That bit is not designed to be run in a hand held router

With a diameter of around 44mm you're living waaaay too dangerously

Ian

Ian, the router bit that I have is about 20-25mm diameter from memory.

Given the projects I have committed to plus what I am proposing to do in the future I am currently inclined to go with clamps from Frontline engineering - you know the ones that clamp the boards level before they apply edge pressure. They are expensive to be sure but I figure if I feel that if I am not using them enough to get my moneys worth I could try to sell them at that point.

As far as the glue line bit goes, it makes sense that it increases the glue area and therefore the strength of the joint, while helping with alignment. On a US site one person reckons that they glue line joint actually decreases strength, but I can't see how it could. However, given that the strength of the glued joint is going to be stronger than the wood itself, it may not be necessary for strength purposes alone.

Bayzz comments are noted and as it so happens I am in the process of getting a Carbatec 2 hp spindle moulder, which I hope to report on after using it for a while. However, I think with the Frontline clamps alignment won't be a problem and I could get away without using any alignment aids, provided the boards were all equal thickness.

This may seem like a silly question to those who have experience with the glue line profile joints, but apart from initial alignment, does it make any difference to the way the boards behave after clamping? ie is there any difference in the tendency for the glued panel to cup or bow, all other things being equal?

Originally Posted by TP1

This may seem like a silly question to those who have experience with the glue line profile joints, but apart from initial alignment, does it make any difference to the way the boards behave after clamping? ie is there any difference in the tendency for the glued panel to cup or bow, all other things being equal?

Face or back sawn boards will have more of a tendency to cup whereas qtr sawn won't. But if you were to alternate the face/back sawn boards,ie, one facing down and next up, you'll reduce the cupping effect across the whole top