Puzzle Cabinet

Puzzle CabinetI’m delighted to say that the cabinet is finally finished and delivered. It was a long haul, and I’ve learned a great deal from it. It’s huge – eight feet wide – this is the first time I’ve been able to get far enough away from it to get the whole thing into the picture.
But at least if I do anything like it again it will happen a lot more quickly now that I’ve learned more about how large oak boards behave.

Finished with an American ‘wipe-on poly’, which is water-resistant and durable, and most of all, easy to apply and dries very quickly.

The client is fitting the lighting strips and the glass doors; when I see it loaded and complete I’ll add a photo of the result – watch this space.

Cabinet ongoing

cabinet try assemblyOne step forward, two steps back. Just cutting a rebate in one of the sides to locate the shelf, and realised that the side had bowed across the grain by at least two millimetres – bummer! and I had already cut it to width! Will this oak never stop moving?

OK, so what you do is, you get the track saw out again, set it up carefully (takes ages) and cut along one of the joints (the cut itself takes a few seconds), then when it relaxes do the lolly stick trick (see earlier post), clamp to stop it moving sideways but not in such a way that you put the wood under stress, and cut again. Theoretically you should have a nicely fitting joint, but for some reason that I haven’t yet been able to fathom it took three attempts. And in fact I did two of the three joints, because having cut the centre one, one of the two halves was also bowed so I split that one too. It looked as though one of the boards would need to be replaced, but thankfully it seems OK now. There will be a little more flattening to do but it shouldn’t take off more than a mm or so, still within allowable limits.

So anyway, this meant that I had to re-do the front fillets (lips? I don’t know the terminology, but I mean the L-shaped piece on the front of each side that hides the edges of the glass doors when they’re closed and generally makes the cabinet look chunkier), because I’d lost 5mm with all that re-jointing. I mean they call the blade ‘thin kerf’ but it’s 2.2mm which is plenty. So I went back to the timber store, more time taken out, and got some more wood. Luckily the weather is reasonably mild so it isn’t too hypothermic in the garage, so I got on with cutting the fillets on the table saw leaving some leeway for jointing.

By the way I’ve discovered that this oak really doesn’t like the router. Even with a brand new cutter it was tearing pieces out, even going a tiny bit at a time. The table saw seems to do a better job, and leaves me with offcuts which if nothing else can go in the fire. The compost bin already gets plenty of sawdust.

More on flattening

Well, you remember I said in a recent post that it’s essential to hold the board down while you level it? Actually I’ve had second thoughts about that. Basically it depends on how important it is that the board should hold its shape in the construction. If it’s fixed on all four corners and preferably in the middle as well, then you’ve saved wood by clamping it down. If it needs to be flat, i.e. not twisted at all, because it’s holding something else in place, then it’s better to let the board relax (perhaps hold it down in one corner or put a spacer under at least one corner so it doesn’t rock), flatten one side under the gantry then turn it over (at which point the side you’ve just done should sit flat on the table) and do the other side. Worth doing the ‘wrong’ side, if there is one, first. You’ll end up with a board that stays flat, as long as it’s not too thin by the time you’ve finished. That depends to a large extent on how well you glued them together in the first place, and of course whether you decided to risk putting a wonky board in between two others to persuade it to behave. Definitely worth dry-assembling edge-glued boards with biscuit joints for several weeks indoors before jointing and gluing. Also a good idea if you have multiple boards of the same length to have a symmetrical pattern of biscuit slots so you can interchange boards later if necessary.

Two more tips:

Make sure your cutter is sharp, otherwise you’ll be sanding out tiny gouges in the wood afterwards. I used a dish cutter because it has a flat bottom but curved sides, so any gaps or inaccuracies from the gantry are at least quite smooth and will sand out more easily.

card spacer on routerSecondly, do the flattening in multiple passes, not all at once. This makes the pass easier on your muscles, the router and the router cutter, and reduces the risk of the router tipping, which makes a deeper cut at that one point. It also means that you won’t take too much off and find the board is too thin when you’re done. I found that increments of the thickness of a business card is about right. It takes twenty minutes to do one pass on an eight-foot by 19″ board; it’s worth the extra time to do several passes.

After the penultimate sanding, I also sprayed the board with water and wiped it down , then let it dry. That raises the grain, so the board feels rough. Another quick whizz with the ROS at 24o grit makes it silky smooth again.

Flattening a large board

router flattening jigHaving my large boards now jointed and glued, I now need to flatten them. Mulling over the problem in the small hours, I remembered an idea I’d seen in a book on homemade jigs. It’s a very simple idea; just make a gantry across the board that lays flat on the bench and has a slot just wide enough for the widest guide bush I have. The gantry was made from 25mm ply – the 18mm wasn’t quite rigid enough not to dip a tiny bit in the middle under the weight of the router. The jig sits about 5mm above the board and holds the router at the same height relative to the bench, so all I have to do is insert the dish cutter and set it to the right depth to skim the bumps off the top.

router flatteningAt first it didn’t seem to work very well; I tried going along and across and generally scribbling around with the router, but the result was a very uneven surface to which the belt sander was hardly equal. Since this is the ‘wrong’ side of the board it doesn’t matter – it won’t show – so I was undeterred.

I decided to try going across the board, moving the jig a little and coming back across. I got the hang of it quickly enough and did a couple of feet at a time. I let the router cool down while going up the grits with the random orbital sander to smooth the bumps, which were now much more predictable and recognisable. It turns out that I didn’t need the belt sander after all. smooth with ROSNo bad thing; the ROS is much gentler, even on a coarse grit.

I started with P80, then P120, P180 and finally P240. It took me just over an hour to flatten the whole 2.4m board. A sigh of relief was heaved. I know how to proceed, and I’m confident that it’ll be a good result. The only thing to watch for is the depth stop on the router, which does occasionally slip when I knock it accidentally.

It’s also essential to clamp the corners of the board down on the bench for this job. The flattening is relative to the bench, not the board, so the board has to be flat on the bench. For some boards it will also be necessary to clamp along the sides too; that just means I move the clamps as the jig is brought across. Similarly the corner clamps have to be moved when the jig is brought to each end of the board.

Jointing long boards

jointing setupWell, the jointing idea worked, thank goodness. The idea is that you’re not relying on each edge being perfectly straight, you just want the two edges to match each other, so you cut both edges at the same time. That way it doesn’t matter if the guide isn’t perfectly straight. I did, however, try to get it as straight as possible using a piece of thread stretched along it before tightening up the join between the two pieces of the guide.

I was casting around for a suitable spacer for the boards; it makes sense to have them close enough to cut both edges, but sufficiently apart to cut off the minimum amount of wood. The kerf of the saw blade is 2.2mm, and I found that a lolly stick is 2mm thick, perfect. Then I found that the lolly stick has a nasty habit of falling between the boards which makes it awkward to fish out again, so the solution was to drill a tiny hole and fit a piece of wire as a cross-piece. lolly stick

I’m managing to joint one board per day – that’s three joints per board. Seems slow, but there are several steps in the process: first check that the joint needs adjustment – about two-thirds of them have so far – then set up the saw guide with the lolly sticks and lots of clamps to hold the boards flat on the table, do the cut, undo the clamps and check that it’s OK, if not do it again. Then the guide has to be manhandled somewhere (I’ve cleared a high shelf) while I re-do the biscuit slots which again needs lots of clamping to make sure the board is flat on the table. Then test again and finally set up for gluing, and leave the clamps on for at least half an hour before moving it aside for the next one.

On the subject of gluing, I’ve discovered silicone brushes. Work a treat and easy to clean. I’m using Titebond III on this job.

All the 6-foot boards are done now, I’m halfway through doing the first eight-foot one. I’m glad I tested the concept on the shorter boards first.

And now I’m thinking about flattening the boards. Never had this problem with plywood… I’ve got a belt sander and a random orbital for going up the grits, but I think I’m going to try starting with a jig for the hand router to skim off the top before sanding. Watch this space.

How do you joint an eight-foot board?

Oak cabinet model
Oak cabinet model

Latest project is a display cabinet, and it’s a big display cabinet. Eight feet wide by six feet high by nineteen inches deep, made from solid oak with glass shelves and sliding glass doors.

Jointing, just to be clear, is getting the long edges straight and square so that when you glue them together there’s no gap. There’s a way of doing it on a planer, or on a router table, but that only really works if the table or fence is long enough to ensure that the board is at exactly the same orientation throughout the pass. Not an option with such a long board on my kit. Push it through the table saw? Same problem.

So it’s a case of putting the cutter to the board, rather than the board to the cutter.

First I tried using the hand router with a bearing guided bit against a straight edge. (You may notice I’m using old business cards as spacers on the second side.)

router jointing
router jointing

The trouble there is finding a  long enough straight edge; I thought the piece of ply I was using as a table was straight, but it turned out to be just a fraction of a millimetre concave. That was enough for a perceptible gap in the middle, which wouldn’t clamp shut, and in any case you want to minimise stresses in the wood.

Next I tried using the circular saw on a guide rail. I have two 1.4 metre guide rails which I can join in the middle. Trouble with this is that you have to set it up again for each board, and however tightly you screw the joining pieces on the rail, there is still some slop. Result: some of the joins are OK, but some aren’t. And I don’t have wood to waste; I want to take as little off as possible.

I tried using a hand plane, but not for long. Wonderfully satisfying in a spiritual sort of way, but still not accurate enough. I don’t have the ten thousand hours with a hand plane.

Finally, in the small hours, I hit upon a solution. The edge doesn’t have to be straight, in the Newtonian sense; it just has to fit the edge next to it. If you clamp both boards together under the guide rail and cut along both edges at the same time, they ought to fit exactly.

acclimatisingI shall try that soon. Currently the boards are sitting indoors, dry-assembled with biscuit joints and acclimatising, because I’m still not sure they aren’t going to move as they reach equilibrium with indoor humidity levels. I’m working on the short boards for the shelf dividers at the moment; they are small enough to be jointed on the router table.

Standing desk finished

Standing desk in use, complete with fairy lights
Standing desk in use, complete with fairy lights

Well it took me a month to build, but that included a lot of figuring out and making jigs. For example, one problem is getting a hole drilled perpendicular to the face of the board. My lovely little router – and it is a Festool – doesn’t put the bit exactly in the middle of the guide bush. All routers have some offset, and this one is about 2 millimetres, which is plenty if you want to drill a neat hole in exactly the right place on a board. So I had to make a jig – just a piece of 9mm ply with a hole to fit a guide bush I happen to have whose diameter coincides with a Forstner bit I happen to have – and marks on the edge of the hole to line up with the markings on the workpiece. Putting the marks in the right place was a pain, and so is lining the jig up and clamping it down for every hole.

router drilling jig
router drilling jig

Tip: always use at least two clamps, as far apart as possible but even if you can only get them an inch apart that’s good enough to stop the piece from pivoting on a single clamp. Clamps aren’t shown in this picture, but the jig is nearly a metre long so there’s a good chance for every setup that you can get a pair of clamps in somewhere.

Another clamping tip: the single-handed quick-release ones are fine for holding the piece in place while you go and get a proper F-clamp, but don’t rely on them for the actual cut. And there’s one type in particular that has bitten my hand more than once – try it in the shop before you buy and don’t buy a clamp online on the strength of the blurb.

Of course after I’d finished making the holes I realised that the guide bush screws allow for a bit of adjustment – there’s me trusting Festool to be so perfect and yes, it has a couple of millimetres of slop. So now I centre the guide bush on the bit by eye – and hope it doesn’t move during a job. Even Festool kit has let me down in that respect before.

Obviously the desk had to be knock-down – it wouldn’t go up the stairs and would cause a back injury anyway – so I used threaded inserts and wide-headed bolts, and dowels where gravity would hold it together. Even staring at the SketchUp model for hours on end there are still engineering decisions to be made as you’re going along and some dowel fittings got converted to bolts late in the build.

I finished the desk with Tru-Oil, which is made in the US by Birchwood Casey for, of all things, gun stock finishing. Not cheap but dries much more quickly than the usual Danish oils you find in the toolshops. It a favourite for musical instrument makers too.

New workshop and standing desk started

DCIM100GOPRO

I’ve moved most of the tools up to the bedroom vacated by Elder Sprog, with the result that a) I now have a warm place to work – the garage is certain hypothermia in this weather – and b) I’m getting a lot of exercise moving stuff between there and the garage, where I still have to do the big stuff like cutting 8×4 sheets. Bandsaw, planer and table saw are still in the cold place, the rest is now cosy and dry. Still need to sort out lighting though. Meanwhile I’ve been asked for a stand-up desk for a freelance web designer, so that’s the current project. It’s going to be birch plywood – rapidly becoming my favourite material to work with and also highly recyclable; when a piece of furniture is no longer needed it can just be dismantled and made into something else. I mean yes, you can do that with any wooden pieces but I’m developing a good production line of boxes and chests from plywood because I like it and it behaves itself.

desk design1This is the idea for the desk, done in Sketch-Up. It’s to go in a corner and fits into a one-metre square footprint. That deep conduit along the wall is a challenge for the corner support.

So I’m having fun with the long cutouts in the uprights at the moment. Making a template first, because it’s very easy to make a mess of it and ruin the workpiece, especially on the join between the straight line and the half-circle, which even with rounded edges is going to show if it’s not perfect. There are myriad ways, as always, to skin this particular cat but what I’ve done so far is mark the shape, clamp on a circle template, go round with the router using a guide bush, set up a straight edge, go along it with the router and repeat steps 1 and 2 for the other side and end, leaving me with a cutout 3mm inside the line; the idea is to go round again with the flush trim router bit against the circle template and straight edge. What I should have done was to go round roughly – well within the line – with the jigsaw and then finish with the flush trim router bit. C’est la vie – setting up for a cut takes ages, and I’ve got to do it all again! But it’s all practice. Anyway when the template is done, I can do the same on the workpieces but without having to match up the guides for the circle and the line each time. And once I’ve got the template, watch out for cutouts just like it on other pieces:-) It’s a great way to lighten the piece, and gives me more offcuts for the little boxes.