How to attach bookcasetop

Dave Siddle · 21 Feb 2021

Hi,

I'm new to woodworking though I've been turning for a few years. I'm building a bookcase in pippy oak with a resin and spalted burr elm top. My problem is how to attach the top securely but still allow for movement. Essentially it forma a T junction and both elements are around 40mm thick. I want the fixing to be as discrete as possible. The only thing I can come up with is routing in a dovetail slot from the back of the piece and slide the top in. This would work, but given I'm new to this and what my materials have cost, I could probably do with a lower risk solution!

Any pointers much appreciated people.

David.

Jacob · 21 Feb 2021

Stub tenons. What movement are you expecting - surely the sides and the top have grain going the same way?
Very thick material! Very large bookcases can be made with 25mm or less carcass and 15mm shelves (assuming redwood or better)

Argus · 21 Feb 2021

Trying to get a mental picture of this....
Is it a tall bookcase with a flat top and an overlapping cornice? If so, gravity will keep it in place.
I've done this in the past, leaving the option for another bookcase of the same height to be slid alongside and a decorative modification in the top/cornice to conceal the join.

Yojevol · 21 Feb 2021

I presume from your description that the top is low down and in full view. I'm not normally a fan of dowels but in this case I would consider using them. You have a lot of meat there, 40mm, so some substantial dowels, 20mm say, could be the answer. In this case the dowel holes in the underside of the top will be blind so a method of transferring positions from the sides to the top will be needed. One method is to make plugs from the dowel material, drill a hole through the centre of each plug and screw in a screw such that it protrudes right through. Place the plugs in the dowel holes in the bookcase sides such that the screw points are protruding. Place the top onto the screws and press down. A blob of bluetack placed roughly in the right positions will help record the exact points. Have fun in extracting the plugs

A short lead-in taper on the dowels will help when it comes to assembly.
Brian

Robbo60 · 22 Feb 2021

Yojevol said:
I presume from your description that the top is low down and in full view. I'm not normally a fan of dowels but in this case I would consider using them. You have a lot of meat there, 40mm, so some substantial dowels, 20mm say, could be the answer. In this case the dowel holes in the underside of the top will be blind so a method of transferring positions from the sides to the top will be needed. One method is to make plugs from the dowel material, drill a hole through the centre of each plug and screw in a screw such that it protrudes right through. Place the plugs in the dowel holes in the bookcase sides such that the screw points are protruding. Place the top onto the screws and press down. A blob of bluetack placed roughly in the right positions will help record the exact points. Have fun in extracting the plugs A short lead-in taper on the dowels will help when it comes to assembly.
Brian

I decided to use dowels to do something similar (but just in plywood) and bought some "dowel guides" (if that's what they are called) Similar principle to above but ready made.
1. Drill holes in the top of the sides
2. Place dowel guides in holes - it is simply a piece of metal same diameter as dowel with a small point on top
3. Position top then tap with rubber mallet or place a piece of protection on
4. This leave a small mark showing where to drill

Dave Siddle · 22 Feb 2021

Thanks for all your replies. I havedowel guides, but the problem here is potential movement. The grain in the sides and shelves runs the same way, so no issue there; the problem is with the top. The whole unit will only be around 900mm high; the base will be attached with a combination of dowels and half lap; shelves will simply be resting on tonk strips. The top is a piece of spalted burr elm I will be setting in black epoxy such that it provides a cornice to the front and sides. It is movement in this relative to the oak side panels that concerns me. It will also add some strength to the piece. The reason the oak is so thick is simple; it's what I have! Unfortunately I have no access to a bandsaw to rip them down, or a thicknesser; besides, I like the look of them. I'm an arboriculturalist, and I'm building this to house my collection of specialist literature on the subject.

I hope that this additional information may help.