Two joint based questions

[robin_shepherd]

I have two joint based questions, I imagine the answers are fairly simple but I'm just looking for some agreements or some pointers on better methods!

1- I am making a bookcase out of 18mm plywood. I plan to use a router to cut 18mm rebates out of the verticals for the horizontal shelves to fit it (please see attached image). I don't want to use pins or screws to secure the rebates on the outside of the bookcase as I don't want any filler on show whatsoever. I will glue the joins. What is the best way to clamp the joint? There will be three rebate joints over a 700mm span. So far I have thought of using a ratchet straps. I'm just wondering if there is a better method than this?

2- I am also planning on using some slotted joints for the internal structure. I plan to use an 18mm router bit along a straight edge to cut the slots (also see attached image) my question now is will the radius left by the router cause any problems when the wood gets slotted together? I can't imagine why it would be a problem as long as I go an extra 9mm further to take into account the radius of the bit.

Any thoughts or tips would be much appreciated.

Thanks!

 

[RogerP]

It would look neater if you stopped the grooves before the front face.

 

[AndyT]

The best way to clamp this would be to have a joint at the top and bottom of the overall box which has better mechanical strength to stop the outside verticals being pulled apart. In conventional construction this could be plain dovetails at the top, concealed by a cornice, or else lap dovetails. At the base you could use a sliding dovetail or plain dovetails concealed by a base. That's not much help if you just want housing joints and a plain ply box.


To answer your question about how to clamp - it depends on the depth. If it's fairly shallow, pairs of sash clamps would work but could soon get fiddly if you are trying to assemble too much at once. For deeper shelves you might need chunky wooden bearers, as long as the piece is deep, possibly planed to a slight curve so as to give some pressure at the middle.

I have used small nails, driven in from below the shelves, diagonally into the uprights, to stop housed shelves from falling out while being glued, and that worked well in softwood - they disappear in the shadows under the shelves. Plywood would be trickier if it is hard or prone to split at the edges.

 

[monkeybiter]

Re. the slotted joints; bear in mind that in your criss/cross structure the horizontal shelf will only be supported for half it's width [i.e. where it sits in the slot of the vertical divider]
In my experience it's best to position these unsupported edges to the rear, the front edges take the brunt of any rough or careless use. This would mean you have a continuous horizontal edge and interrupted vertical edges.

 

[RogerP]

... or instead of cutting plain grooves you could cut sliding dovetails, not difficult with a router and of course they are self locking and glue unnecessary.