The Bench Build-Part 4: Benchtop Done

[Master-of-None]

What is left now are the front and the back of the bench where the mortices are located. The next picture shows the five boards that were needed for the two front mortices.

   

In dry fitting all the pieces, I realized it was going to be very difficult if not impossible to keep every board aligned, especially when the glue was applied and everything became slippery. My solution to this was to set up a dry fit with all the boards and the stubby legs. Then I proceeded to drill holes in strategic places to keep everything in place. Next, the glue will be applied, pegs will be pounded in, and then everything will get clamped.
The next two pictures shows the dry-fit after the holes were drilled:

   

   

The next pics show everything clamped up with the dowels, and then with the clamps removed:

   

   


Just some quick cuts with a saw and no more dowels:

   

I did the back mortices the same way as the front. 
Next, it's time to start assembling the top. I thought it might be easier to do that in two parts, in other words, glue half the boards to the front mortices and the other half to the back mortices. Then just glue the two halves together. The following picture shows the first glue-up of the mortices with a two board laminate. 

   

[Master-of-None]

The rest of the two-board laminates were added the same way until I ended up with two halves of the benchtop. When I laid the two halves together, there was clearly a gap. It appears that someone put a bow in there 
. When I applied clamps across the two halves I was able to close the gap, but I did not feel comfortable in doing that when there were so many boards that needed  to be squeezed. So out came the handplanes and an attempt to get rid of the bow:

   

Putting the two halves together again I realized I wasn't done. It seemed that I did get rid of the bow but there was some twist as well. So they came apart again (at about 90 lbs per side it was not an easy job), to get rid of the twist:

   


After quite a bit of work that I'm not good at, I did manage to get rid of most of it. At least it was good enough for me (actually I was concerned I would mess it up if I tried to make it better.) In the next pic you can see there is still a gap but in reality it was very small and only a small amount of pressure from the clamps closed it completely:

   


Everything looks good now for the final step, the bench top:

   

   

[bandit571]

Looking good, so far
....better eat your Wheaties before you try to move that too far...
..have help for when you lay it down to trim the ends...

[arnman]

Looks great. I was wondering how difficult it would be to do the glue-up and get the front and back pre-made mortises perfectly aligned, but it looks like you got it.

[Master-of-None]

Looks great.  I was wondering how difficult it would be to do the glue-up and get the front and back pre-made mortises perfectly aligned, but it looks like you got it.

arnman, it was actually not difficult at all. I worried about that as well but then realized that only in the final glue-up I had to be careful. 

bandit, from what I can tell, the top should be about 170 to 180 pounds. I got that estimate from weighing one of the laminates and then just multiplying. And when I do need to move the top, I call my son to give me a hand. No way could I do it by myself, especially when it's on those unstable saw horses.

[adamcherubini]

So, what did you do about the gap? Did you plane it all out? If you didn’t it will probably be back. Tite bond is not amazing in flat wise tension. I suggested one lamination per night for this reason. Failing that, I typically plane a hollow (spring) in a long joint like that. The theory is that the preload stress relieves as the boards shrink. Hard to say it works in my experience, but it’s a good theory.

The key remains to protect that end grain after you cross cut. I believe protecting end grain from moisture loss is the real reason for breadboard ends. Maybe that’s something you could think about. Could serve 2 purposes:
1) legitimately protect end grain
2) eliminate the exposed gap if any of the boards separate.

I guess you could also consider clamping the end really hard, then doweling the bb end on to maybe compress the ends a little. I’ve done something like this in the past, but never with dowels. More, frame and panel or dining table stuff. So I’d appreciate your thoughts.

BTW, How did you do with flatness across the top?

Regarding the gap and the flatness, no wood stays where it was over time. These are workbenches not granite surface plates. I nail stuff to mine pretty regularly. It’s not flat or straight or perfect in any way. This bench is gonna be awesome.

[Master-of-None]

Adam, to address some of the issues you bring up, not necessarily in order:
as soon as I got the top together I couldn't wait to see how flat it was. I looked at both sides, the bottom and the top surface. Both are OK but not perfect. I didn't spend a lot of time on this but it looked like about 1/4 inch or so out of flatness. I haven't done anything about it yet, since I'm working on the legs now. Once that's done I'll flatten the top. The bottom will probably stay the way it is, maybe remove some of the glue squeeze out.
As far as sealing the end grain, yes, you have a good point. I wrote myself a reminder on the bench top itself, in pencil: SEAL END GRAIN. That will have to wait until the rest of the bench is done. Then I'll turn it over, stand it up and cut off the uneven sides. And then seal the ends.
The gap, yeah, I was concerned about that. As I mentioned above, I did the best I could and then glued it up. There was some pressure needed to seal the very small gap, but I thought it was minimal and should not affect the integrity of the joint. I guess I'll see!

[arnman]

 Tite bond is not amazing in flat wise tension. 

Adam, do you have an alternate glue recommendation?  I would still expect Tite Bond to be stronger than the grain in the perpendicular direction, but I have not looked into that.


Master-
I do agree this bench should be awesome.  I am glad you are working so quickly.  I am always looking for your updates.

[Master-of-None]

arnman
Thank you. 
My understanding is that long grain to long grain glue joints are stronger than the wood. I'm not sure what Adam was thinking about and I hope he chimes in to explain further.

[adamcherubini]

All the glues, even epoxy, have published similarly high bond strengths (in excess of 3000psi). To be fair, they mostly test and document lap shear, not tension. Less well known is the fact that these bonds strengths are highly dependant on joint fits, clamp pressures, and surface preparation. I think its fair to expect considerably less structural capability from our glues than the manufacturers' test coupons indicate.

Woodworking myth: Glue is stronger than the wood.
This is generally NOT true. Wood is many times stronger than any glue in many ways. In flat wise tension, some woods are very strong and may well be stronger than glue. We know what these are based on our experience. Beech is a very strong and very isotropic wood, excellent for tools and workbenches. Flatwise tension is about 1000psi and shear is 2000psi. Tension and compression could be many times greater than any glue. Beech compressive strength is 6000psi. Tension is twice that again or 12,000psi. (aluminum could be 40-80,000, Steel 150,000-300,000psi). Oaks are similar. Maple is up there. We know what they are.

The myth comes from the failure modes - the way the specimens are loaded and the fact that for some directions, glue really is stronger than wood. I just wanted to make the point that we shouldn't take that for granted. If we are expecting glue to hold a project together, we may be disappointed.

For this project specifically, the gap at the end of the bench required clamp pressure to close. We can expect that the glue, not only has to fight the project's desire to pull itself apart, the glue joint itself was likely disadvantaged by not having sufficient clamp pressure. On top of that, differential shrinkage at the ends of the board, will create the additional forces trying to open up a crack. I think the OP can expect a crack next winter (depending on where he is)

Is it a big deal? No absolutely not. But as woodworkers I think its super helpful to share our stories and discuss what we did wrong, what went well to help make us all better woodworkers.

My thoughts (not that it matters or anyone asked- I'm just chatting):
1) I almost always spring joints in wide boards. The OP basically had that opportunity having built up 2 separate laminates. I would have planed a hollow in that joint.
2) Because we expect more shrinkage at the ends, I have in the past concentrated my clamps on the ends and had a single clamp in the center of projects like this one. I have 8 or 10 4' pipe clamps I use for these things. I may put 4 6" apart at the ends of a 8' project (or something similar- you get my drift).
3) Having glued up my share of projects with what I considered a flaw like this, I've not been reluctant to rip them (realizing I do this with a handsaw) re-plane and re-glue. That option is still open to the OP. (I'm not recommending it, just talking about the subject).
4) In terms of glues, I much prefer tite bond to all others for invisibly thin bond lines. I have used hot hide glue extensively for these joints and I don't prefer it. For one, I feel I don't have enough working time to get clamps on. Second, I feel hot hide glue benefits from a discernible bond line thickness (like epoxy). Too much clamp pressure, and the joint becomes starved of glue. That said, I routinely use rub joints for non-structural joints. I generally feel working with hot hide glue is more fun than all other glues and makes for a lego-like build process.
5) My original recommendation was to glue up the front of the bench, then add a board each night. Only trick with that is if the boards are soft like these may be, the clamp pressure becomes localized, not spread across the entire face as we would want and expect. In the past, I've used cauls or stiff members to squeeze the boards together like a press.

Tite bond requires high clamp pressure to develop full properties (depending on the wood, can be as low as 100psi or as high as 250psi). It is not stiff in and of itself and cannot transfer load across a gap like hide glue or epoxies can. Without clamp pressure, its strength is a fraction of its max or full strength.

Fundamentally, that makes it the wrong choice for all unclampable joints (T&G, M&T, dovetails etc). All of these are better glued with epoxy or hide glue.