Thread: Traditional work bench - let me run some ideas past you...

Originally Posted by Groggy

Give me a yell if you need some sash cramps or longer besseys to clamp it up.

Way ahead of you I've already got four sash clamps (borrowed), 6 pipe clamps and the threaded rod to clamp the top together with. What I really need is a big bench to build it all on... catch 22.

Thank you kindly for the offer, sir, I may just take you up on it in a pinch.

I don't know how to put these tops together without making a mess. The best way is usually to put some cling wrap or paper over the clamps and table-top, Sit the timber on its side and roll the glue on. Then roll each piece as you put it on edge and build the top.

You mentioned threaded rod, are you going to have that pass through the top? If so, make sure it won't interfere with the dog hole pattern. Don't think you need it though.

This top will have to be made in a few sections I think. The dog hole sections and the rear support may or may not have to laminated, but either way these will be used for clamping all of the other sections.

The front section is only five lamination plus the dog row, the centre section is eight laminations plus the dog row, and the rear section is 15 (!!) laminations plus the rear support. Christopher Schwarz - though he was using 2x4's for his top - glues only two boards at a time, then glues the two new boards together into 8" wide sections. Once dry he cleans up the joining faces and assembles the entire top. I like his approach, but it's a lot of work with this many laminations.

Instead, I think I'll build the sections two or three boards at a time. This will take considerably longer to finish, but I can be a lot more certain that the end result will be straight and true. And because the boards are a lot narrower (19mm) I won't have to worry so much about getting the faces perfect, there'll be plenty of flex to meet an imperfect glue face.

As for whether I need the threaded rod, I probably don't. The example of this type of bench top construction that changed my mind about threaded rod was Thumbsucker's bench. He built it with West System and it still split and warped. I have a feeling it was as much to do with timber choice and condition as anything else, but the lesson is there to be learned all the same; mitigate risk using any means necessary. So, threaded rod and 1" dowel for assembling the top!

I haven't yet developed a perfect procedure for this, but I've still got time to think about it

My bench was put together in two pieces. First I glued up two 300mm slabs. Then I put each of them through the thicknesser to tidy them up. After that they were joined and clamped into one piece. After fussing with a hand plane it was within 1mm across the entire top.

Hi Kman - this may be a bit heretical, but you are probably fussing unnecessarily about glue. Most of the joints on a bench top aren't under very much stress in normal use, & the glueing surfaces are so generous that things hang together pretty well. Mine was put together with a PVA glue of dubious pedigree well over 20 years ago, and no joints have failed, although a couple have opened slightly at the surface because the wood wasn't as dry as it ought to have been when I made it.

One small change to your design I would suggest is to reverse the dovetails on the front left hand side. It's only a minor point, but this joint could see some stress from expansion of the top, so it would make sense to me to stick with the traditional orientation of tails on the side piece, pins in the front. I would also forget about bolting it all together with threaded rods. Although it's intuitive that they make everything nice & tight, after the first couple of deep moisture cycles, they will have crushed the wood enough that they will be doing nothing. I went to this trouble many years ago, & found exactly that - at the end of every dry spell, the rods were loose. So IMO, they are not worth the bother. Haven't used them on a half dozen benches built since, and all are holding together extremely well. I have also read the same advice from others in various places. I've been asked to 'fix' so many items over the years where people have tried to overcome poor design with various metal bits, but they never work! Metal & wood should be mixed with great care.......

Cheers,

Originally Posted by IanW

One small change to your design I would suggest is to reverse the dovetails on the front left hand side. It's only a minor point, but this joint could see some stress from expansion of the top, so it would make sense to me to stick with the traditional orientation of tails on the side piece, pins in the front.

I realised yesterday when I was adding bolt holes for the end caps that I'd oriented them wrong It the design pictured I wouldn't be able to attach the end caps after the top was laminated at all! Whoops. Thanks for that.

Originally Posted by IanW

I would also forget about bolting it all together with threaded rods. Although it's intuitive that they make everything nice & tight, after the first couple of deep moisture cycles, they will have crushed the wood enough that they will be doing nothing.

I'll admit that this concerned me a little, but I'm more concerned about the top de-laminating. It makes sense to me that a top laminated from 19mm boards will have a lot more glue surface per volume than usual, but I don't know that this is enough. I've never done this before, so I will submit to your expertise if you're confident.

Dave.

Originally Posted by kman-oz

................... so I will submit to your expertise if you're confident.

Dave.

You've put a heavy burden on me there, Dave! I shrink from any word with 'expert' in it - just speaking as someone who has made most of the mistakes it's possible to make, & am now making some for the second (or even third!) time.

However, I'm reasonably confident that if your glue surfaces are half decent, and especially if you are using a low-creep type glue, there will be oodles of glue holding those suckers together. And anyway, if the joints are so poor that the rod ends up being the only thing holding the laminates together, it's going to be a bit of a wonky show all round....

Cheers,

The idea of the threaded rod is to apply support to the glue bonds, rather than become a bond of last resort. I come from a long line of 'Over Engineering' graduates, I don't think I've made anything that wouldn't last at least a life time.

I've never actually seem a bench top build with threaded rod, so it might be fair to suggest this is unnecessary. The over engineering instinct is very strong The fact that the timber is all the same species, has been well seasoned and has now had some time to acclimatise bodes well for pure glue bonding. I just need to prepare the surfaces well is all.

bugger.....
....just typed out a reply on a glue up jig for your benchtop... then went back and saw from the sketchup drawing that you are face jointing, not edge jointing, the boards.

.... bugger.... its not a bad little jig either.

that'll teach me to not read the entire thread first!

I missed your post Clinton. Regardless of the jointing style, I'd be very interested in your jig. Edge joining is something I never manage to do well, so post up anyway!

Back to the subject of glues, I've done more reading on the subject of woodworking glue than I can reliably relay the substance of given a matter of days in which to do it. Thus, I've been around in a dozen circles, change my mind about thirty times before settling on good old Aliphatic Resin - Yellow glue to the rest of us, in the form of Tite Bond Original, just like I though in the first place.... I've also been reading Douglas Adams again and recently feel remarkably like Aurthur Dent suddenly faced with an infinite Universe to unravel.

Regardless of my research, one element of yellow glue eludes me: exactly what is the difference, chemically, between white glue (Polyvinyl Acetate or PVA) and yellow glue (Aliphatic Resin)? I know all about the various properties, relative strengths and weaknesses, application and countless other subjects which I need not have bothered reading about, but the difference in their chemical make-up is elusive.

Specifically, yellow glue and white glue share their chief active ingredient; Polyvinyl Acetate. Little reference is made, however, to what has been changed to make yellow glue superior in woodworking.

This is very slightly annoying in very much the same way as an empty coffee cup on your desk is subconsciously annoying. You need it, it's right there, but there's something altogether missing from it.

Please help!

Dave.

Dave - as I understand it, the yellow glues are basically the same, but are set up to provide more cross-linking as they polymerise, making them stronger, a bit less plastic at higher temperatures, & a bit more water-resistant. The extra strength is probably less important, but the other properties are valuable.

P'raps there is a lurking industrial chemist who can step in and explain it all in molecular detail.
Cheers,

Just to confuse the matter even further I may have struck the key to this dilemma: While yellow glue - which is a little misleading in it's description as Aliphatic Resin - is still PVA based, it has simple additives introduced that create simple Aliphatic carbon chains during curing.

This could be described a low-level cross-linking. The process is only semi-reversible in moisture and considerable less likely to deteriorate with heat. Standard PVA has no cross-linking at all and is more susceptible to these elements.

In fact, the next step up the chain is a proper cross-linked PVA. These have Polyaliphatic agents which produce complex cross-linked carbon chains taking the moisture and heat resistance properties even further.

If an industrial chemist has an opinion on this it's more than welcome. I didn't even take Chemistry in High School At least I think I have all of this straight in my head

I've incorporates Ian's suggestions regarding the dovetails on the end caps and front/rear aprons... finally. This one includes a few other minor changes to aid the construction process, the most significant of them involved moving the central dog holes.

Attachment 71850 Attachment 71851

Initially I had the central row of dog hole slots cut into the side facing the front of the bench, as opposed to the front row of holes where the slots are cut into the rear facing side. Of course, this would have required me to make two separate jigs for cutting the dog hole strips; one with an 88* angle and another with a 92* angle. Instead I've flipped the central dog hole strip and cut them into the rear facing side of the strip so I can use the one jig for both strips.

....

Then I realised I'll have to make a second jig anyway, for the opposing dog holes in the tail vice.



At least this way it'll be easier to be perfectly consistent.

Originally Posted by kman-oz

.......Then I realised I'll have to make a second jig anyway, for the opposing dog holes in the tail vice.



At least this way it'll be easier to be perfectly consistent.

Yup - I've not been able to figure out any other way! From my experience, I wouldn't fuss about the exact angle of either set of dogs. Even vertical dogs don't seem to pull out - at least not wooden ones (which I prefer to use). Maybe the metal ones do. The main problem I've had is getting them to hold in position while you are setting something up, especially after they are worn & crushed a bit with use. Have tried several remedies, like making wooden springs, but the best & simplest solution has been to drill a hole in one side & put in a bullet catch (saw this in a 'handy hint' in FWW, too obvious to think up myself!). Put some on opposite sides of different dogs, so if they do wear the dog hole a bit, you can swap for one with a catch on the other side. (But I haven't had a problem yet, even after 12 years or so of regular use, somewhat surprisingly).

Cheers,