Best way to attach legs to an OSB chair?

[skint-94]

Hello everyone, before i ask, i am pretty new to woodworking and there's something that i need to know before i tackle it!

So basically I'm going to be making this:

chair but there's a problem and that's attaching the legs to the actual seat.

I'm going to be gluing 3 cut outs for the legs together and 2 cut outs for the seat and then i want to use 4 screws on each side, 2 of them would go into the rest and the side of the leg and another 2 for the seat which would also go through the side but my main worry is strength! so I'm hoping that having at least half the thread going through the face of the leg and the other half going through the edge would keep it strong or would just be loose and flimsy?

I want to use some Confirmat screws which as far as i know would be fine but i need to know if it really would work or not?

So yeah what do i do? also sorry for this being so long, to be honest you could just see the picture and see what i mean lol

Anyway i'd appreciate any help

Thanks!

 

[YorkshireMartin]

Is anyone going to be sitting on it or is it just for art?

 

[Wuffles]

Is anyone going to be sitting on it or is it just for art?

Splinter groups will use it.

 

[YorkshireMartin]

Is anyone going to be sitting on it or is it just for art?

Splinter groups will use it.

Cmon now... :lol: (hammer)

 

[jonnio]

I'd glue it together with 25mm dowels, not all the way through so you can see them but like floating tenons between the sides and seat. If you are laminating sheets of osb to get the thickness you could have an extra bit/layer on the inside of the sides that the seat could sit on to help with weight.
I think though that osb is not sound enough to last in this structure. But I hope you manage it as it's a cool design!

 

[MattRoberts]

Looks cool, but I've got a feeling it would tip backwards with a sneeze...

 

[AndyT]

Looks cool, but I've got a feeling it would tip backwards with a sneeze...

I agree. That might be why so many less unconventional chairs have their back legs splayed the opposite way. I don't want to rain on your parade, but it's possible that your design looks eye-catchingly different because it reverses an important design aspect of a chair for sitting on.

 

[Aggrajag]

Use Gorilla glue and you won't even need screws!

 

[John Brown]

I would definitely do what jonnio suggested, re. an extra thickness of OSB on the bottom part of the legs/arms.
I would also lose the leaning back look, as I'm guessing that, if you stuck to right angle, the seat and the back could be the middle parts cut out of the legs/arms. Although that's just me being cheap. Probably not artistic...

 

[skint-94]

Right i've had a little thought about it and I've read some of the replies too which have helped and I've come up with 2 options! First one would be jonnios suggestion, so I'd glue 2 dowels into the side of the leg, back rest and the seat, then use the screws into the end of the solid wood dowel which would hopefully keep the screws in firmly and would lessen the risk of them coming out or ripping through the face of the wood over time.

I also thought that maybe i should use corner brackets! 4 of them to secure the legs to the seat and another 4 for the back rest which also connect then legs to the rest!

 

[ED65]

If you're adding dowels to the edges and then want to screw into them you're going into end grain. Confirmats might work acceptably well for this but it's generally something to try to avoid. Generally if you want to install a dowel to improve screw holding you put it in at right angles to the axis of the screw, so it enters long grain which can hold on to the threads properly.

In addition to this the larger hole drilled into the OSB might weaken it more than the screw holes would have in the first instance, making it more prone to delamination.

 

[MatthewRedStars]

It's a bold industrial design - I'd consider bolting all the way through the OSB into the seat with the bolt heads showing and nice wide washers.

 

[skint-94]

If you're adding dowels to the edges and then want to screw into them you're going into end grain. Confirmats might work acceptably well for this but it's generally something to try to avoid. Generally if you want to install a dowel to improve screw holding you put it in at right angles to the axis of the screw, so it enters long grain which can hold on to the threads properly.

In addition to this the larger hole drilled into the OSB might weaken it more than the screw holes would have in the first instance, making it more prone to delamination.

So if i was to glue a dowel, ideally an oak dowel at a right angle and then place a screw through the side of the legs and through the face of the dowel then it should be strong enough to hold it? Because i was thinking that i could actually drill a hole through the back of the rest, right through so it would help fasten the leg to the side of the rest

 

[skint-94]

It's a bold industrial design - I'd consider bolting all the way through the OSB into the seat with the bolt heads showing and nice wide washers.

I was thinking that but I'd need to find a tool that would go the whole way through the rest and seat

 

[Jacob]

It's a bold industrial design - I'd consider bolting all the way through the OSB into the seat with the bolt heads showing and nice wide washers.

I was thinking that but I'd need to find a tool that would go the whole way through the rest and seat

You wouldn't drill all the way through you'd just leave a gap for the bolt in the middle lamination (have to be three).
In fact it's a trad way of making up big industrial type table tops and similar from boards - drill the outer members for the threaded rod but square mortice the inner ones to leave space for alignment.

 

[skint-94]

It's a bold industrial design - I'd consider bolting all the way through the OSB into the seat with the bolt heads showing and nice wide washers.

I was thinking that but I'd need to find a tool that would go the whole way through the rest and seat

You wouldn't drill all the way through you'd just leave a gap for the bolt in the middle lamination (have to be three).
In fact it's a trad way of making up big industrial type table tops and similar from boards - drill the outer members for the threaded rod but square mortice the inner ones to leave space for alignment.

Oh i see, that makes sense to be honest, i do have a habit of doing things or thinking about doing things the hard way lol

 

[nev]

as above but if you don't want the bolt heads/ nuts on show, countersink them into the sides and then fix the last outer laminate sheet over them, with posh screws as per the drawing, or from the inside/ underside with screws for an invisible fix.

 

[Lampy John]

Love the industrial look and feel of the chair.

 

[ColeyS1]

I'd use box steel for the legs, seat and back, then just clad it/cover it in osb. That certainly make it much stronger and it could then be bolted together.
Tonight I've reglued a traditional kitchen chair for my neighbour that decided to come apart after somebody sat on it. Luckily his head just missed the kitchen worktop before he landed on the floor. Could have been much worse !!
I'd cringe everytime someone sat on that, the legs look as though they're going the right was to collapse when loaded.


Coley