unit construction

[mooretoolsplease]

Evening all,
got a job coming up for a customer who wants an island unit for her kitchen. i've added a couple of drawings of what she wants.
The only difference is there will be another shelf in the side where the bottom shelf has grooves.
I've got a few reservations here, one being that with a huge slab of granite on top, and no back as such to keep it all square, there might be some movement in the whole piece.
Second is that she wants it all out of solid oak, no mdf anywhere except for drawer construction.
How would the forum go about joining the bottom shelf to the sides allowing for wood movement?

[engineerone]

i would think you need to put an apron at the top to properly support the granite.
as for the bottom shelf, sliding dovetails seem sensible.

hth

paul

[sainty]

If the grain on the shelves runs left to right, rather than front to back (which it will have to do to accommodate the grooves) there wont be any issues with wood movement.

I agree however that you are likely to get racking in the piece without any bracing. Could you get some form of cross member underneath the drawer box, somewhere in the middle where it can't be seen, or at least wont be so obvious? Sliding dovetails for the shelves would give you the best mechanical strength but would be tricky over the width of the unit.

rgds

Stu

[jfc]

I'd be tempted to use a few wedged mortice and tenons , sort of finger joint like . My first thought was a sliding dovetail but i dont think that would stop any racking that may happen sending a huge lump of granite onto someones foot

[mooretoolsplease]

There is 4 drawers ont he unit, so in between the drawers down the middle i'm going to add some tight fitting bards to act as a brace, and the same between the legs, they wont be able to see it unless they are on their hands and knees.

[engineerone]

how about making lipped torsion boxes for the
uprights and the top and bottom shelves??

oak and granite are going to be very heavy together.
have you checked the floor capacity?


paul

[jfc]

how about making lipped torsion boxes for the
uprights and the top and bottom shelves??

There you go , go to Ikea and buy it in ;D

[mrgrimsdale]

One way or another you are going to have to brace it like a trestle table. A deep rail between the drawers? Another one under the bottom shelves? Through tusk tenons with wedges even.

cheers
Jacob

[modernist]

If you have access from both sides you could put a divider in the bottom spaces to stiffen it up

Brian

[engineerone]

ok jason ok i satnd embarrassed

however, i am certain you need to support the granite properly
in the centre as well as the edges, so maybe you should have
the drawers only able to open to halfway on either side, and in the middle you have a deepish stop which is also the support for the top.

as for the bottom maybe jacob's idea is really good, tusk wedged tenons on the outside would give it a really neat look.

paul

[jfc]

I think tenoning the bottom shelf would look better than tenoning a hidden rail . Still put the hidden braces in but hidden is how they should stay .
I was thinking like this





A tusk tenon although a very strong joint is for first fix , second fix use is for looks i would say and would be a weaker joint than a through mortice and tenon .

[tusses]

does the customer need the clean sides ?

My 1st thought would be to make it a table with drawers 1st'most and frame/pannel for the sides / center.

some of which has been hinted on above.

[mooretoolsplease]

I will add rails under the bottom shelves, and between the drawers, im hoping this will add to the ridgidity of the unit.
I think the frame and panel ends is a good idea. I will make them like this.
For the shelves apart from the one with the grooves, I will make these out of lipped MDF.
I am thinking dominos and pocket screws to hold it all together?

[dom]

I wouldn't mix mdf and solid oak in the same unit, only lipping.
I would brace as suggested under the drawers and shelves and as you suggested use dominos, this would be the quickest way.

[engineerone]

if the braces are visible, then it is worth making them shaped to add a bit of interest to what is looking very square and boring

paul