Bench Top Question


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Hey everyone, I'm making a new bench, and have glued up 3 sections of the bench top in anticipation of gluing the 3 sections together. I had to do it this way because of the open time on the glue. I was following Chris Schwarz's directions from his 2007 PW article on the $175 Workbench (do it in sections and run them through the planer to minimize the amount of hand plane flattening required).

Picture%20003.jpg

When I did the final assembly of the top, I found that I had to apply incredible clamping pressure to close the gaps (the F clamps were bowing).

Should I be concerned by this? If I were to do it again (and I won't for years hopefully!) do you have a recommendation on gluing up the top?

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F-clamps are good when you just need a moderate amount of clamping pressure. If you need a lot of clamping pressure, then you might want to think about getting some parallel clamps. The bar on F-clamps is just a little too thin. I know that bow fairly easy when I crank on them. As for being concerened, as long as you got then to close up, and the clamps are left on for enough time then I think that you will be fine..ANd make sure you post some pics and let people know what you think of that bench design.. they are kind of a hot topic around here..

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I hear ya. I do need to invest in more Parallel clamps. I have 2 right now and I don't think too highly of them (Samona brand). Good for small jobs, but maybe need to start looking at some Bessey or Jorgansons.

I will be sure to post pics. I'm also currently blogging about it

F-clamps are good when you just need a moderate amount of clamping pressure. If you need a lot of clamping pressure, then you might want to think about getting some parallel clamps. The bar on F-clamps is just a little too thin. I know that bow fairly easy when I crank on them. As for being concerened, as long as you got then to close up, and the clamps are left on for enough time then I think that you will be fine..ANd make sure you post some pics and let people know what you think of that bench design.. they are kind of a hot topic around here..

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I have a feeling that the glue may have added some thickness over the course of 8 boards to varying degrees. So there may have been a bit of a wave to the face. I did use a planer to thickness them down to size and had no issues in gluing up each section.

Was everything flat? No twist? Parallel clamps will give you more clamping pressure, for sure, but in your photo, you have some hefty F-style clamps and I'm wondering why you are needing to clamp down so hard.

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When I did the final assembly of the top, I found that I had to apply incredible clamping pressure to close the gaps (the F clamps were bowing).

Should I be concerned by this? If I were to do it again (and I won't for years hopefully!) do you have a recommendation on gluing up the top?

When doing my benchtop glue up, I did spend some time using a plane on the gluing surfaces to make sure that they mated well so that I wouldn't have to use a huge amount of clamp pressure to bring the last sections together. If it took you that much clamp pressure to close the gap, there's a chance that they might delaminate over time, but it's just as likely that depending on how you are going to mount the benchtop on your base, the base might resist that delamination.

As far as whether F-clamps are suitable for a benchtop glue up:

IMG_7676.JPG

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I'm a big fan of the Jet parallel clamps. I've broken Jorgensons and the design on the Besseys aren't as good as the Jets. IMHO

Now all that I have are the Jorgy's. I will agree that their older ones are kind of crappy.. But the new version is A LOT better. I luckily only have a few old ones. I am however, thinking of making the switch to the Jets.. I think that they are just a little nicer. The Jets and Jorgys were rated at the top of a Fine Woodworking review.

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Did you dry fit the sections together before the glue up to check for gaps? You should be able to lay the boards as they would be glued up and use some light source from the opposite side to check for gaps.

Wood may move (bow, twist or cup) if allowed to sit after you plane or joint it. It is best if you can glue it up as soon as you finish planing; especially if you use lumber that is not completely dry.

If you do end up with gaps remember it is just a workbench not a piece of fine furniture. As long as you end up with a workbench that is a usable tool that is all that matters.

Just my opinion.

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I'm a big fan of the Jet parallel clamps. I've broken Jorgensons and the design on the Besseys aren't as good as the Jets. IMHO

I too value my growing collection of Jet Parallels, but I'm surprised no one has mentioned pipe clamps for this type of glue-up. They are capable of a lot of clamping pressure and are more affordable starting point. Plus as an added bonus, you can easily swap out pipes of different lengths to vary the capacity as needed.

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When I did the final assembly of the top, I found that I had to apply incredible clamping pressure to close the gaps (the F clamps were bowing).

With sub-assemblies this big, it'll be very difficult to bend them to your will with clamping pressure to close gaps. I followed a similar process when I built my benchtop, and I found that after doing the initial glue up, the edges of the three sub-assemblies all needed to be re-jointed in order to get a nice tight fit between them. All the glue and clamping pressure that you apply when building the sub-assemblies tends to deform their edges a bit. If you already finished your glue-up and you have some gaps, you can always fill them with some epoxy.

Dave

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With sub-assemblies this big, it'll be very difficult to bend them to your will with clamping pressure to close gaps. I followed a similar process when I built my benchtop, and I found that after doing the initial glue up, the edges of the three sub-assemblies all needed to be re-jointed in order to get a nice tight fit between them. All the glue and clamping pressure that you apply when building the sub-assemblies tends to deform their edges a bit. If you already finished your glue-up and you have some gaps, you can always fill them with some epoxy.

Dave

I was thinking the same thing on the epoxy. If I ever need to do it again ... (hopefully not)

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Did you dry fit the sections together before the glue up to check for gaps? You should be able to lay the boards as they would be glued up and use some light source from the opposite side to check for gaps.

Wood may move (bow, twist or cup) if allowed to sit after you plane or joint it. It is best if you can glue it up as soon as you finish planing; especially if you use lumber that is not completely dry.

If you do end up with gaps remember it is just a workbench not a piece of fine furniture. As long as you end up with a workbench that is a usable tool that is all that matters.

Just my opinion.

I did, but the Schwarz mentions in his article that once your sub assemblies are glued up, there should be little-to-no wood movement, so I didn't think too heavily on it. Lesson learned.

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I too value my growing collection of Jet Parallels, but I'm surprised no one has mentioned pipe clamps for this type of glue-up. They are capable of a lot of clamping pressure and are more affordable starting point. Plus as an added bonus, you can easily swap out pipes of different lengths to vary the capacity as needed.


I have to agree with your assessment about the pipe clamp, good clamping pressure and economical . They do have perceived shortcomings though, The biggest being that they bow when used, and they do, when not used properly, there is a learning curve involved and some skill required to using pipe clamps. Harder to use because you have to move gizmos at both ends of the clamp. Heavy and hard to store. Ugly and just not as nifty looking as those darn F clamps.


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Hey everyone, I'm making a new bench

Picture%20003.jpg

When I did the final assembly of the top, I found that I had to apply incredible clamping pressure to close the gaps (the F clamps were bowing).

Should I be concerned by this? If I were to do it again (and I won't for years hopefully!) do you have a recommendation on gluing up the top?


You have heard the saying" you never have enough clamps" well now you know what it means. you were simply asking too much from your clamps. In a perfect world your clamp spacing may suffice, but in the real world your clamp spacing should be 12in. minimum and preferably 6-8in. and when thickness nears 3in. plan on both sides getting clamped .

Don't be worried about the gaps your bench will hold up for ever, just fill them with some epoxy prior to leveling after glue up.

And here is a tip: mix up enough epoxy to coat the end grain of the bottom of your legs, for obvious reasons.

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I have always been taught that if you cannot close a joint with hand pressure you need to do some more work on it. With this statement in mind then it should not matter what kind of clamp you are using. Now on to the real world. Big thick assemblies like this are very hard to close with hand pressure when you cannot get your hand around it. In the process of making the sub assemblies you are introducing significant moisture with the glue and not necessarily evenly so you are bound to see some warping. I used this same method when build my bench, but before gluing together the sub assemblies I took a jointer plane to the edges then a block plane to the center of the joint to give it a little spring that would tighten up the edges. If nothing else, removing this meat from the middle gets that stuff out of the way of closing the ends. In other words if you are killing yourself to close the gap, you might think about jointing the edge. Big pieces like this really are best jointed by hand. Now that you have them joined however I would not worry too much about it coming apart. Good, modern adhesives and the introduction of more moisture into the dry side of the board will help to equalize the top. Plus as Dave said above, just fill the gaps with epoxy if they bother you.

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It as already mentioned here, but I wanted to weight in on this a bit more - if there were gaps that the clamps would not close - than the sub assemblies were not flat enough to make the final glue up.

gluing up a tope like this should not really require so much pressure as long as the boards and joints are flat and tight.

When more pressure is required though - I like using pipe clamps, those have tremendous pressure at a bargain price. I can't afford any parallel clamps myself.

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Ya know I hate reading things that stick in my head but then can't remember where I read them so that when questions pop up I can't site the resource, but Google is my friend so let it be your friend too.

There are two factors/components to consider in glue ups: Cohesion and adhesion.

Cohesion is the bonding of "like molecules". This is the type of bond that happens when you have loose joints with a "lot" (relatively speaking) of glue in the gaps that form due to not enough clamping force. All glues used in wood working do not provide a good cohesive bond (aka joints will fail due to weakness) with the exception of Epoxy. NOTE: That introducing the humidity in the glue will affect the wood slightly.

Adhesion is the bonding of "unlike molecules". An adhesion bond is mega-strong. This is the bond you really want in wood working and in order to get it you need a razor-thin glue line.

LQQK

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A workbench top is a tall order for any clamp, save possibly a small army of pipe clamps.

The reason you need to go bonkers on the clamps is simple: The two surfaces don't mate perfectly. (OK, duh.) Jointing a table top or door panel made of 4/4 stock is one thing. A 4" thick stack of whitewood is another animal altogether.

When I did this, I adapted a trick from Charles Neil and did these joints in two stages. He gives this as a technique for fixing a split board with a band saw, but the principle is the same.

a.) Create your subassemblies at whatever width you intend to put through the planer. I was aiming for a 24" wide top and wanted to baby my planer blades, so I did four 6" wide planks.

b.) Joint the edges of these planks ballpark true. Doesn't have to be perfect at this stage.

c.) Provisionally glue the planks together, but don't worry about closing the gap completely. Instead, focus on using transverse cauls to keep the top flat across its width. If there are gaps between the subassemblies, that's OK.

d.) Go back to the saw and re-rip the top apart, cutting through the temporary glue joints between subassemblies. Be certain to use a very sharp and very coarse blade (24 teeth or fewer) as this is a deep cut and will push most saws to the stops.

Sounds like extra work, but kerfing and regluing gives you two perfectly mated gluing surfaces. And, if your saw blade happens to be a fraction of a degree off true, it doesn't matter. (Any inaccuracy cancels itself) You can now glue things back together a final time and be assured that a.) the top will be flat and b.) the joints will be tight without having to go all ubermensch on the clamps.

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The reason you need to go bonkers on the clamps is simple: The two surfaces don't mate perfectly. (OK, duh.) Jointing a table top or door panel made of 4/4 stock is one thing. A 4" thick stack of whitewood is another animal altogether.

It's actually not too much trouble to use a hand plane to achieve a good mating surface for this type of joint. That's what I did for my benchtop glue up, as noted above. I would imagine that the hand planing would be easier than gluing, cutting, and regluing the joint.

Here's the final product.

IMG_4997.JPG

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It's actually not too much trouble to use a hand plane to achieve a good mating surface for this type of joint. That's what I did for my benchtop glue up, as noted above. I would imagine that the hand planing would be easier than gluing, cutting, and regluing the joint.

Here's the final product.

IMG_4997.JPG

Nice bench man!! I like it!!

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Sounds like extra work, but kerfing and regluing gives you two perfectly mated gluing surfaces. And, if your saw blade happens to be a fraction of a degree off true, it doesn't matter. (Any inaccuracy cancels itself) You can now glue things back together a final time and be assured that a.) the top will be flat and b.) the joints will be tight without having to go all ubermensch on the clamps.

That's approximately how I glue up panels, but I do it without the preliminary glue up. It's common for Festool tracksaw users (now DeWalt and Makita, too?) Here's how:

Put the first 2 boards side by side with a small gap smaller than the kerf of your blade.

Lay down the guiderail showing just a little of the leftmost board (kerf gap is to right).

Plunge and cut. Even if the blade isn't perfectly 90° to the guiderail, it won't matter as the angles are complimentary.

Push the boards together and use a fine pencil to mark a couple registration lines.

Put board 1 aside, repeat above for boards 2 and 3.

Works very quickly. Only caveat is to use a good blade that doesn't leave kerf marks everywhere. Slight marks aren't a problem.

Actually, I use the tracksaw to edge joint boards (face joint on a planer sled if necessary or just successive skip planing). So much faster and you can put the guide exactly where you want the edge; useful when the grain is skew to the long dimension.

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So I remembered that there was a video of this done long ago, but I cannot find it and I know it was hosted at WorkshopDemos.com (RIP no longer up). The description above should be enough, though I could record something if that matters.

I also wanted to add that you can do this with a router as well if you have a track-like guide for it (read: strip of MDF and the edge guide of the router). Have the boards < 1/4" apart and run a 1/4 compression spiral bit through the kerf. While the TS-75 operation I described above doesn't need a lot of clamping (guide holds down the left board, right board held down by splinter guard), you will need the right-hand board clamped down; depending on the direction you push the router, one board is on the normal cut side, the other on the climb-cut side. I did it this way a couple times before getting the TS-75.

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