Shelving Joint?

[stuartpaul]

I've been tasked with making a set of display shelves for my main client.

These are a decent size (300 mm square 'boxes' 200 mm deep) and will be 15 mm thick oak.

My initial thought was to use a slot joint (to my shame don't know what they're actually called!)

Accuracy is clearly important and I'm wondering if this is the best joint to use (can't think of another that is a realistic option) and the best way to cut them?

 

[DTR]

I've made something similar from ply, using your slotted method (I think of it as a very deep cross-halving joint). However I would be cautious of doing it in oak for fear of the unsupported half splitting off along the grain.

How about making the uprights full length, with housings on both faces to admit short horizontal sections?

 

[Jacob]

I'd most likely have the horizontals going through full length as they are load bearing, and the verticals cut as partitions to slot in between them, with a shallow housing in the horizontals.
Your half housing would do for small light-weight stuff but not for anything substantial

 

[MikeG.]

As per Jacob and DTR, although I'd consider having the bottom shelf full length to facilitate fixing, and for over-all robustness.

 

[rafezetter]

I've made something similar from ply, using your slotted method (I think of it as a very deep cross-halving joint). However I would be cautious of doing it in oak for fear of the unsupported half splitting off along the grain.

How about making the uprights full length, with housings on both faces to admit short horizontal sections?

This might work but would depend on the method of fixing to the wall.

I made a smaller display unit using the same method, and unfortunately broke a section at the halving joint - to repair it I drilled 2 small steeply diagonal holes and inserted bamboo kebab scewers to reinforce the glued joint.

If I was going to make it as per your design above I might be tempted to do the same across the back part of the halving joint on the outermost unsupported sections if you were going to use those areas for display as well, but instead of bamboo scewers - metal bars epoxied in - coathanger wire or similar. You could even do it 45deg across the assembled joint from the unseen back.

 

[Mr T]

You could use the method you suggest but additionally house the front half of the horizontals into the verticals but 5mm or so. This would provide support for the front half.

Chris

 

[stuartpaul]

Thanks for the useful comments. If I change to full width horizontals my concern is the lack of ‘meat’ for any housing although it will help with the more economical use of available timber!

With 15 mm stock I can’t see how I can go deeper than 5 mm and retain strength? That really doesn’t feel as if it will be strong enough or am I missing something? I’ve thought about a sliding dovetail if that would add to the strength aspect.

Mr T, - that might work quite well, I’ll give that some more thought.

 

[AndyT]

I think the real answer is that shelves like that are only really suitable for lightweight items on a small scale, where the deep slots work ok.

Maybe you could make it work on the scale you want by using dowels. I know they may be unpopular or thought of as not proper woodworking, but they are suitable for 15mm thick material and you can cut long dowels so they will join two verticals on the same line, above and below the horizontals.

 

[dzj]

Rout a ~10mm deep groove at the back of the horizontal shelves and insert a spline.
That should hold the unsupported half.

Something like this:

A small notch to accommodate the spline would be needed in the vertical piece.

 

[Jacob]

Thanks for the useful comments. If I change to full width horizontals my concern is the lack of ‘meat’ for any housing although it will help with the more economical use of available timber!

With 15 mm stock I can’t see how I can go deeper than 5 mm and retain strength? That really doesn’t feel as if it will be strong enough or am I missing something? I’ve thought about a sliding dovetail if that would add to the strength aspect.

Mr T, - that might work quite well, I’ll give that some more thought.

The housing is only needed to locate the vertical partition and make a tidy joint but as you say 15mm is too thin for the design. However you did it, it would need close tolerances and any timber movement (loading, drying) would open up gaps. As drawn, 15mm is perhaps not possible
Back to the drawing board!

 

[stuartpaul]

Rout a ~10mm deep groove at the back of the horizontal shelves and insert a spline.
That should hold the unsupported half.

Something like this:

A small notch to accommodate the spline would be needed in the vertical piece.

Ohh, - I like that! Bit of metal rod and some epoxy and jobs a good 'un.

That's a very practicable, simple solution that allows me to keep to the original design dimensions which whilst not uber critical were something I didn't want to increase.

That said I'm going to look at thicker timber and some other dimension alterations and see what it looks like.

Thanks for all the helpful comments.