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Awkward clamping problem

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MarkDennehy

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Remember Mark, type "l" and not "r" by mistake...

So I have this project in mind (shelves) but I can already see this awkward bit in the construction and I'm looking for ideas to get round it.
Picture if you will, a normal bookshelf with housing joints and two to three shelves. Easy to clamp up if you have to, easy to drive the shelf into the dado with a mallet as well.
Now curve the front of the bookshelves out in a nice graceful curve across the front (keep the back edges simple and straight). Still easy enough to assemble.
Now curve the front edges of the sides of the bookcase so they have a nice graceful curve from floor to the top of the bookcase. Still readily doable though the mallet is now the easier option than the clamps.
Now angle the two sides of the bookcase outward by, say, 15 degrees or so (so they're still vertical, but each is rotated around a vertical axis running through the back corner of the bookcase).
The design now looks beautiful, it has a few functional good points I don't want to lose because of the intended final application. Very, very roughly (missing several curves, with exaggerated angles, and ignore the bits outside the sides as that's just me having issues with sketchup as I'm rusty using it), it looks like this in my head:



But...

How the pineapple do I clamp the shelf into the housing joint? Or mallet the shelf home?

I'm running through a few idea in my head, but not having done this before, I can see myself standing in the shed with components that are marginally too large to work on comfortably, staring at curing glue and a joint that won't seat and no way to convince it to do so, and I'd rather avoid that one :D Has anyone come across this problem and solved it before? Would ye mind telling me the secret? :D
Thanks!
 

ColeyS1

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I wonder if you could temporarily clamp something to the front edge of the shelves to aid with getting the clamps on.
I did this tricky repair earlier in the week

The only way I could think of clamping the arm back on was to change the direction of the clamp by adding an extra clamping spot.

How about a dovetailed housing .....lol

Coley

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novocaine

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clamping cauls and a hot glue gun.
or the lutherists trick of 2 bits of masking tape and some super glue.

both are easy to remove once complete, hot glue just needs a touch of heat, the other peels off.
 

Jamied

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Great design,
I would use a few ratchet straps, one for each shelf joint.
Good luck
 

Pete Maddex

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Solid wood or MDF etc?

MDF shallow dado and screw/fill, solid dado clamping blocks/ratchet straps Spanish windlass etc.

Pete

Pete
 

MikeG.

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If this is a corner cabinet, then the outside of the verticals are going to be hard up against a wall. In which case, you could pin or screw through those into the shelf edges and not have to worry about clamping.
 

Sgian Dubh

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Obvious potential solutions include:
*1. Tapered sliding dovetail for each shelf to side joint - relatively technically challenging to execute but very effective and eliminates the need for clamps.
*2. Technically simple tongue and housing joints formed with a router, apply glue, assemble, nail together, fill nail holes, apply finish (it seems likely the sides butt up against a wall or something similar so evidence of nails would be hidden.) Slainte.
 

ED65

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Clamping cauls, if that's what wedges would be called in this context, were what I was going to suggest but I wonder if ratchet straps (or a Spanish windlass) would actually work better?
 

custard

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MarkDennehy":2lze1bjr said:
How the pineapple do I clamp the shelf into the housing joint? Or mallet the shelf home?
With a normal bookcase it's actually the back that's responsible for much of the rigidity and keeping the two sides together. Here you've got a relatively small back for a relatively large bookcase, and the rebates along the back edges of the sides would have to be precisely angled to accommodate the back, that or the edges of the back would have to be precisely angled.

It's a bold design, and well worth pursuing, but I think the cramping problem is actually only a minor part of the challenge (and one easily solved with cramping blocks, look at your sketch up illustration, consider the protruding part of the shelves as cramping blocks and you're virtually there).

The bigger question is how to prevent the two sides separating from housing joints, and how to build in enough rigidity? Glue blocks under the shelves? Through fastenings from the outside into the shelf ends? Sliding dovetail joints on the ends of the shelves? Kregg screws going up at an angle from the underside of the shelves into the housing joints? Dowels or dominos? Through tenons?

There are lots of options but you'll need something.
 

MarkDennehy

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Pete Maddex":1hdr9ap1 said:
Solid wood or MDF etc?
Solid wood - poplar for everything bar the bottom shelf, walnut for that. Bottom shelf would be 1" thick, sides 1", other shelves 3/4" (y'know, to within handplane milling type tolerances).

Spanish windlass
That's a new one on me, but I get the idea, it's like a garotte for furniture...
 

MarkDennehy

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custard":26u6ab4t said:
Here you've got a relatively small back for a relatively large bookcase
Worse, I had none at all in mind, I was thinking of something like Paul Seller's leaning wall shelf project:



It's a bold design
I'm not kidding, I literally heard that in the same tone as Sir Humphrey saying "That's a very brave plan Minister" :D

The bigger question is how to prevent the two sides separating from housing joints, and how to build in enough rigidity?
...
There are lots of options but you'll need something.
There was me thinking a tight housing joint and titebond would have sufficed :(
Well, at least it's at the drawing board stage now, fixes are cheap at this point 'cos all I've done so far with the wood is to put the poplar in the sun to get a tan so I can see what the boards will look like without that green stain that's on some of them.

Doing a sliding dovetail seems to be a common idea that solves the clamping and the attach-the-sides problems, but I've not done one before and since the sides are sloped it'd be only over a shortish (9-10 inches) distance in the middle of a shelf. I suppose I could cut the dovetails parallel and run them fully along the side of the shelf up to the little bit at the front that I want to have come out wider than the sides to hide the joint from the front, and then fit it into the side from the front, seat it and cut off the exposed unused parts of the dovetail on the shelf during construction before the final glueup. Or mark off the boards, and only cut it on the bit that'll be in the side (I'm just thinking about how to fit one into the other during the assembly).
 

custard

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MarkDennehy":387eresw said:
Spanish windlass
That's a new one on me, but I get the idea, it's like a garotte for furniture...
Forget it, that's the worst cramping solution, something you only do when you've judged every other option impossible. Band cramps don't actually bring much pressure to bear at 90 degrees to the glue surfaces, if you delve into the geometry of how they work they're more trying to turn a square section into a circle.
 

custard

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MarkDennehy":3ft7g1ff said:
Doing a sliding dovetail seems to be a common idea that solves the clamping and the attach-the-sides problems, but I've not done one before and since the sides are sloped it'd be only over a shortish (9-10 inches) distance in the middle of a shelf.
Have a go cutting sliding dovetails with a router on some scrap.

It's not hard to make a joint that will guarantee the shelves will never pull out of the sides, but that joint will likely still be a bit loose, so the bookcase can rock and sway a bit. The challenge is to make the joint snug enough so that it prevents racking, but still loose enough that you can get the shelf home without a sledgehammer.

The huge advantage you've got is that the angled sides on your design will by themselves resist racking, so you can get away with fractionally looser sliding dovetails than would be required for a normal rectilinear bookcase. Consequently sliding dovetails are an especially relevant solution for this particular situation.
 

ColeyS1

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Screw and pellet it, job done

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MarkDennehy

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Was letting the poplar sun itself today to see if the green would fade (I know I'll probably have to do that again before finishing, but I just wanted to get an idea of what it'd look like) and took the opportunity to sketch out what the side would look like on the material I have, again roughly.



Starting to get a better picture in my head, and starting to agree with the sliding dovetail idea, even if I have to add a peg through from the outside as well to belt-and-braces it.

(ps. ignore the dead patch in the garden, that whole section is due to be rotavated and reseeded once the hot spell breaks)

Mind you, I've never cut one by hand so I doubt I could get it as accurate as required on my first try here so that might be a cheating router job (I can redeem myself by dovetailing the top shelf into the sides by hand :D ). Radian don't seem to do a dovetail router bit and the only one I have is one of those cheap 40-euro-for-a-set-of-twenty-bits ones that I do not want to trust this job to :D Anyone got a recommendation for a good dovetail router bit suitable for sliding dovetail joints in poplar and walnut?
 

memzey

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Wealden are my go to site for router bits. I’m sure they’ll have what you need.
 

custard

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Another vote for Wealden,

https://www.wealdentool.com/acatalog/Dovetail_34.html

Their quality is top notch, their prices are reasonable, plus they've got a pretty wide range. That last point is important, because you actually need two cutters for sliding dovetails,

Sliding-Dovetail.jpg


First you need the dovetail cutter, but you also need a straight cutter (or better still a spiral upcut bit) with diameter "X", or a fraction less than "X". You use the straight bit to basically cut a housing (dado) joint. Then, without changing the fence position (or ideally even the collet, so two cutters with the same shank is good), you swap to the dovetail bit, set the identical cut depth, and finish off the joint having already excavated the majority of the waste with the straight bit.

After completing all the female parts of the joint you then place the same dovetail cutter in a table mounted router, and cut the male component one side at a time, running the shelf vertically against the router table fence. You creep up on the perfect cut, moving the router table's fence back a whisker until you've got exactly the fit you want.

The first time you do it it's a bit of a faff, but the smart thing to do is to record all the key dimensions and keep a test piece from the male cutter set up. Then any subsequent joints are a breeze to set up and execute.

Or at least that's the way I do it, if anyone has a better method please share it.

Try it on some scrap first and shout if you've any questions.

Good luck!
 

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MarkDennehy

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Sounds good, but I was planning to just cut the straight-bit part myself by hand like a housing joint and then set the angles with the dovetail bit, but that sneak-up-on-the-fit approach sounds good to me, and I'll finally get the router table out of the box from lidl :D
 

mrpercysnodgrass

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ColeyS1":38zsgatx said:
I wonder if you could temporarily clamp something to the front edge of the shelves to aid with getting the clamps on.
I did this tricky repair earlier in the week

The only way I could think of clamping the arm back on was to change the direction of the clamp by adding an extra clamping spot.

How about a dovetailed housing .....lol

Coley

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Coley, is that part of a large door hinge you are using to stop the clamp from sliding? What a good idea.
 

ColeyS1

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mrpercysnodgrass":341nw8rg said:
ColeyS1":341nw8rg said:
I wonder if you could temporarily clamp something to the front edge of the shelves to aid with getting the clamps on.
I did this tricky repair earlier in the week

The only way I could think of clamping the arm back on was to change the direction of the clamp by adding an extra clamping spot.

How about a dovetailed housing .....lol

Coley

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Coley, is that part of a large door hinge you are using to stop the clamp from sliding? What a good idea.
Well spotted !!

Yeah I bought them for a project that never materialised so they've got a new use as clamping aids....until something else comes along.

Cheers
Coley

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