Thread: WIP - John's Workbench Mk2!!

Originally Posted by johnredl

....Is it a mortise & tenon joint, or is there a better way of doing this? Going by the pics, how big should I make my tenons...I assume I should make the mortises in the top a little bigger to allow for expansion?

John - gravity will be your friend - the tenons really only have to prevent the top from sliding off the legs, so smal stubs would do it. My bench legs have another cross-piece on top, & the bench sits on those. A single 5/16 coach screw up through each cross piece keps the top firmly in place.

If you are going to mortise the tops of the legs straight into the top, I wouldn't worry about expansion/contraction, there should be more than enough flex in the legs to cope with any movement of the top.

Cheers,

Look what my friend brought back from America for me!!



A new Lake Erie Wooden Screw Kit for the leg vice...sweet! (I did have to pay for it, but my friend was nice enough to bring it home, I reckon I've saved the better part of $100 in freight - think I owe him a big favor)

Now I just need some time to spend in the shed!

Well thanks to the Rasp Group Buy, I've met another WW Forum member. Thanks to Yachtie I've (well "we've" actually) spent 2 days on a saw, jointer and thicknesser and in addition to totally blunting his thicknesser blades, we've converted my old outdoor table from the pic that I posted a while ago into 90mm thick boards ready to be glued and clamped to form the bench top.

Now what I was planning to do, considering that the boards are a bit "banana'd", is to glue & clamp each one to the next, waiting a day between each board for the glue to set. I had a go dry clamping a couple together and it seems to work. I think that the total exercise should take me 12 days! One thing that I am definitely learning is patients...that plus jamming your hand between a chisel and the timber after belting the chisel with the mallet really hurts!

I have 3lt of titebond2 here, I was planning to use that for the glue up, and with the dings on the top, mixing some sawdust with some of the same and filling the gaps. Someone suggested that epoxy might be slightly better for the top filling, but how does this go for re-planing/re-flattening? What does everyone else think...I'm definitely keen to learn from experience

John - if your boards are "bananad" I would not be using a PVA type glue. This stuff goes quite weak at the knees at temps over 40 degrees, which is a pretty common summer temp inside your average metal shed. If you need significant force to pull these boards together, they are highly likely to spring your joints down the track. I would be either using glues with a higher temperature tolerance like melamine or epoxy on boards like that. Or better still, jointing them straight & true so that they can be clampednicely together with little force. But either route would be far less likely to cause you future grief.

Of course, depending on your bench design, a few sprung boards may or may not have any structural implications. My own bench has opened up a bit along one glue line during its first summer in Victoria (which is how I came to 'discover' that PVA becomes plastic at high environmental temps ). But it hasn't let go completely, and even if it did, it would not have much effect other than to annoy the hell out of me, because the top is constrained enough by the end caps.

None of these glues causes any problems with subsequent planing. You can wipe squeeze-out off straight away with a damp rag (water for PVA, metho for epoxy), but this way risks smearing it around, & having odd patches show up on the finish (not a big deal on a workbench, but a right PITA on a piece of furniture!). Better by far, I reckon, to let it cure til it's fairly firm (but not rock hard) & then remove with a card scraper.

My 2c
Cheers,

He's a very good cleaner upperer???. Garage nearly spotless again after a couple of cubic metres of dust and shavings. I think you should go for the epoxy for the glue up. Keep in contact
John

Originally Posted by johnredl

...

I have 3lt of titebond2 here, I was planning to use that for the glue up, and with the dings on the top, mixing some sawdust with some of the same and filling the gaps. Someone suggested that epoxy might be slightly better for the top filling, but how does this go for re-planing/re-flattening? What does everyone else think...I'm definitely keen to learn from experience

Epoxy and sawdust mixed is easy enough to work, ie plane and sand

In reference to the comment that PVA "...goes quite weak at the knees at temps over 40 degrees".

Recently, I started using Selleys Aquadhere Exterior on a few workshop cabinets, mainly because it has a greater open time than Titebond 3 (and it's cheaper).

"Heat resistant to 110°C (bonds will not weaken in exposure to direct summer sun)"
Selleys Aquadhere Exterior - Water Based Construction Adhesive

In summer, the heat inside my shed can reach +44 degrees Celius. I have not noticed any glue failures in my workshop cabinets. That said, I have not tried to glue up boards that are "bananad", which require significant clamping force to bring the boards together.

Mike

Originally Posted by Ekim

In reference to the comment that PVA "...goes quite weak at the knees at temps over 40 degrees".

Many years ago I made a chipboard linen press that stood in our enclosed (un-inuslated) corrugated iron roofed back veranda. The doors were made from used Jarrah (frame) and MDF (panels) glued together with regular PVA. The following summer the doors literally fell to bits after a few days in the first heat wave. I though maybe the timber was not quite dry and the jarrah had just shrunk so I cleaned then up and glued them back together but they fell apart again at the next heat wave. I also have several home made wooden tools that had PVA glued components that literally fell apart under prolonged severe heat. These were stored hung directly under the metal roof in my shed where I know it reaches more than 50ºC. In this case it was probably a combination of glue failure and shrinkage.

Originally Posted by Ekim

In reference to the comment that PVA "...goes quite weak at the knees at temps over 40 degrees".

Recently, I started using Selleys Aquadhere Exterior on a few workshop cabinets, mainly because it has a greater open time than Titebond 3 (and it's cheaper).

"Heat resistant to 110°C (bonds will not weaken in exposure to direct summer sun)"
Selleys Aquadhere Exterior - Water Based Construction Adhesive

In summer, the heat inside my shed can reach +44 degrees Celius. I have not noticed any glue failures in my workshop cabinets. That said, I have not tried to glue up boards that are "bananad", which require significant clamping force to bring the boards together.

Mike

Mike,
I have had PVA joints stand up very well over time, too. In a recent remodelling of the tail vise on my bench, I had to separate two pieces that had been glued with LV GF2002, which is essentially a PVA. Not a single square mm of glue let go, the entire join separated by wood failure. That piece had been glued up at least 25 years.

OTOH, I made a picture frame to hold a moderately hefty picture painted on masonite. I used aquadhere, with no other attachment aids for the corners. All was fine until one really hot day, when there was a sudden almighty crash as several bits of frame & picture hit the floor - leaving only the two side bits dangling by the hanging wire. I immediately blamed the glue, not my questionable construction, and re-glued with Araldyte, but there were no further suicides from that frame. I have had numerous other failures with PVA glues, and particularly on some woods. I'm pretty careful with preparing my edges, and always glue freshly-planed, closely-mating surfaces.

So while I still use PVA quite a bit in situations that are non-critical or I know from prior experience that I can trust it, I guess my experiences have led me to avoid PVA in certain situations. Both physical & chemical properties of the substrate and any tensions on the joint will have a bearing on the longevity of the glue bond, and my problem is I can't always predict the outcome. I haven't tried the 'Exterior' type glue you mention, but it does sound like it has greatly improved the heat tolerance. I would still advise against using 'regular' PVAs in any situation where tension & moderate to high temperatures are involved...

Cheers,

Thank you all very much for the advice. I know there are arguments for and against using PVA, and I do have a fair quantity of titebond2 on hand...but just to be on the safe side I stopped past the Fibreglass and Boating Supply shop and bought some epoxy glue. The last thing that I want to happen is, like IanW said, a couple of boards to come apart a little, and after all the hard work I am putting in, cause an annoyance. After all, I am hoping to have this bench for many, many years!

So I've started gluing (no pictures sorry, I'm sure you all know what gluing 2 boards together looks like!). What I have discovered is that I need to clamp a straight edge to the side to keep it all nice and straight. I was thinking of using some 40mm x 5mm angle steel, as the 2 metre long cementing screed hasn't worked. Seeing as I've never used epoxy on this scale before, I have begun doing a test run by gluing together only 2 boards first.

Also...while I was in the fibreglass shop (Lonsdale, SA) the extremely helpful man was telling me about a product called "Norseal". From what I am understanding and reading on google, its a epoxy sealer that has the consistency of water, and penetrates your wood like oil does. Mr Fibreglass man said it is a great sealer because of the penetration properties (apparently he uses 3 or so coats), but for external use needs to be varnished. Has anyone used this product? Here is a link to the manufacturers site:

Norglass Paints and Specialty Finishes: Norseal Wood Treatment

I had planned to 50% dilute turps & linseed oil for both the top and base of this workbench - do you think that "Norseal" is an option/idea? I was thinking that if it penetrates wood, you should be able plane or sand it back in the future. Alternatively, maybe an option for the base (after glue-up obviously!)?

John - not quite sure what the Norseal is supposed to achieve - it's to "seal & waterproof" yet needs a coat or two of regular finish on top. As it's a bench & not a boat, why not just proceed directly to a finish coat? The main purpose for a finish on a bench as far as I'm concerned is to prevent glue & other spills from sticking to it.

My benches get a couple of coats of oil (commercial D.O. type stuff 'cos I'm too lazy to mix my own brew) sloshed on them, and a good waxing of the top once the oil is sufficiently dry. Dried blobs of glue or varnish can be easily flicked off the resulting surface with a card scraper. I don't deliberately abuse my bench top, & take reasonable care, but over time it will inevitably cop some punishment, so there is little point in going to too much trouble, IMO.

At some point you will probably want to re-plane the top & freshen it up, & the less finish you have on it, the easier it is to do that. I've done mine twice in 25 years, but I notice the intervals are getting longer, & my enthusiasm for pristine tops isn't as strong as it once was......

Cheers,

Well the top is in traction, now just have to wait until tomorrow TI see how things turn out. I've never used epoxy on such a grand scale. I've only ever used tubes of araldite, but I found the basic principle the same.

Also, I've learnt a bit about clamps too. As much as I'd love a full set of besseys, I have to accumulate things slowly. The top 2 are borrowed, and as much as I am appreciative to my friend, they don't have anywhere near enough clamping force (I did a dry run before gluing). I'm using Groz clamp heads that I've put on 50x25x2.5 RHS, they seem to have great clamping force, so they're a great place to start (and only total of $30 per clamp head, $6/m for RHS ).

I weighed each board before gluing. The total for the top is 97kg including the 1kg of epoxy. How am I going to get it up off the floor? I have some friends coming over for a BBQ on Saturday...I haven't told them about it yet (insert evil grin here :> )!!

Originally Posted by IanW

John - not quite sure what the Norseal is supposed to achieve - it's to "seal & waterproof" yet needs a coat or two of regular finish on top. As it's a bench & not a boat, why not just proceed directly to a finish coat?

I was thinking that if the product penetrates the wood like oil but is actually an epoxy, that unlike having to apply coats of oil every so often, that the outer layers that were penetrated by the norseal would become epoxy'ed. Plus I wasn't going to use a top coat as the bench is not uv exposed (Does that make sense? It did in my head!). I was thinking of using it on the base, and using 50/50 linseed/turps for the top. Again, I haven't made anything quite like this, so I posted mostly asking for advice, which I received...thank you

So, linseed for the top...(right? I'm understanding this right?) and something else for the base? Or linseed for both? I have 3 1/2 lt of both turps & linseed, that's why I've mentioned it so much.

Originally Posted by johnredl

So, linseed for the top...(right? I'm understanding this right?) and something else for the base? Or linseed for both? I have 3 1/2 lt of both turps & linseed, that's why I've mentioned it so much.

John, I'd be using the linseed, if I had such an excess of it, & sloshing it generously over the whole thing. As you say, your bench is inside & protected, and doesn't need to be hermetically sealed, so almost any finish you could name would do the job. I used Danish on mine, because like your LO, it was on hand & plentiful at the time.

The downside of linseed is the extended drying time. I have been reminded of that this week, after I soaked a bunch of wooden mallets in some BLO - it's been so long since I used straight BLO, I'd forgotten how long it takes!

Cheers,