Is this joint strong enough?

[elanjacobs]

Hi, No comment re the construction except adding that what wongo has added I agree with. I do question using oregon. Its a soft brittle timber and as the chair racks the fibres will compress and the joints will become loose. I question the longevity of your chair (Unless its a mock up for a design...)

The addition of corner blocks will eliminate most of the racking issue.

[rustynail]

I'm a chair maker. There are several things I do not agree with in this particular design:
1. The bevel end on the back legs should be on the front edge to reduce possibility of back tilt.
2. A horizontal tenon is a weak joint under shear.
3. Corner blocks are essential.

[mitzee]

Thanks for the replies, it's great to be able to tap into so much experience and learn from others.

Rustynail, I understand what you are saying about the rear tapers however the tapers (@ 5 degrees) make the lower section of the leg vertical wrt the ground which I assumed this was a common trait in many chairs which do not have angled legs. Also the seat backs do not extend past the rear legs, my intent here was so the chairs could be pushed closer to wall when not in use and stacked away. I took another look at the photo I posted and realised it is pretty hard to distinguish that the rear legs are angled forward at 5 degrees (photo of different angle attached also).

I've attached a photo of the original picture that I used for these chairs.
Can anyone suggest how they might have executed the joinery without the weaknesses that I have come across or are these just an inherently bad design?

[rustynail]

Those pics help. I can now see that a negative angle has been placed on the rear legs.
Would it be an option to increase the dimensional width of the back rail with tenons into inside face of rear legs as in your current design and the side rails tenoned into the back rail. This configuration allows the full back section of the chair to be squared and glued up, the front section squared and glued up and when these two sections are dry they are joined by the two side rails with the chair standing on a flat surface.
A good way to increase tenon size is scalloped rails. This helps decrease bulk when working in heavy timbers but provides increased section size at all joints.
The chair in the pic was made from old palings. The seat is drop in and sits on the corner blocks. Timber is probably Blue Gum or Red Mahogany (was a bit hard to ID at the time.) Still as solid as the day I made them. Which defies all logic.



IMG_0849.jpg

[wood spirit]

Though Oregon ain't the strongest of woods you seem to have come up with (intuitive?) a good solution as I read the photos. Joints look nice-presume a router was involved- wise, crossing the axis of the 90 degree angles is interesting and makes a lot of sense - use a glue that is both strong but has some give. If you can make a chair work -you be right -Chairs cop more stress than anything else that you are likely to make.

[mitzee]

The chairs have kind of gone on the backburner for a while, I will definitely get around to increasing the thickness of the back rail and making the sides a little shorter to compensate at a future date. The comments and opinions presented have been very helpful.

The chairs have taken a sideline to a desk that I'm working on to use as a computer station, it is made from spotted gum which my wife picked out as her timber of choice (I never new they had such hard wood in the eastern states!).

I'm trying to make the desk relatively light (like that is even possible with spotted gum) but strong and delicate looking whilst including a full width (about 1100mm) drawer to put the keyboard and mouse when not in use.

This has presented me with a problem, namely the joinery for the front connecting rail which I believe I need as there is no apron in the front because the drawer will be there instead.
The front connecting rail is 20mm x 45mm and at each end uses two 1/4 inch tenons (15mm vertical for the leg connection and a 25mm horizontal for the apron connection).
This is probably a rather complicated way of doing this joinery however I couldn't think of anything which would provide greater strength whilst still being small enough to accommodate the drawer and bearing runners that I will be using. The aprons are connected to the legs with 3/8th x 50mm mortise and tenon joints.

Once again I wonder if this joint will be strong enough for the purpose? The table top is solid 20mm spotted gum which is held together with loose tenons. I'm thinking the connection to table top along with this support/brace piece and the inherent strength in the rest of the frame there shouldn't be an issue (I hope).

Nothing is glued up yet so I'm not committed to this method, any suggestions would be welcome.

Pictures attached to clarify my description.

Regards
Bart

[Kuffy]

Thats a fantastic joint you have created. Usually in situation like that I just use 2x8mm hardwood dowels straight into the leg/rail.

20150520_170353[1].jpg

Is there plans for a second rail to be added to the top of the legs? I would encourage it. At the moment, your front legs only have one rail, if I were to grab the legs at the bottom and spread them apart lengthways, the section of the leg above the rail will contract, adding a rail at the top will stop it from contracting adding a great deal of strength and ridgity to the frame. Or...you can add a rail at the bottom of the legs, but since u need to sit at it, you will need to do something like I have illustrated in the image of a hall table I am currently working on. also having a rail at the top of legs gives a place for a timber button to be added to connect the top.

[mitzee]

Adding a rail at the top would certainly give enough strength however it would not leave enough room for the drawer. The apron rails are only 80mm and I want the drawer to fit into the provided space while giving at least 50mm drawer depth. Increasing the size of the aprons would give the extra space but would take away from the overall delicate look that I am after.
The top will be fixed to the frame in 5 places using some kind of wedge and pin arrangement that I am yet to figure out (trying to avoid using any metal except for the slides). I'm hoping that the connection to the table top will provide support similar to the top rail that you have suggested and therefore prevent the legs from being spread apart. I do want to avoid any structure below the aprons as this would interfere with a chair.

I like the hall table, very clean lines. Well done.

Regards
Bart

[Kuffy]

If you are wanting the top to act as a front rail, I would probably put a couple of dowels, or a loose tenon, into the top of the front legs and then make holes/mortises to suit in the underside of the top. I wouldn't glue dowel/tenon into the top though, I would fix it with a screw or two(yay, a use for pocketholes!!!). the side edges of the table and back edge can be held down in normal ways, buttons, those metal clip thingos, screwblocks etc etc.

[mitzee]

Dowels or loose tenons into the top of the legs.... great idea, I hadn't even considered that.
I can't bring myself to buy a pocket hole jig, let alone use one. It is a suitable method of joinery in many instances but just not for me. I do very a very low volume of work and get my joy from the joinery challenges with the goal of trying to create a piece using wood alone, with the exception of metal drawer slides (just can't find a way to get as good a result without them, soft closing and push to open). I use a lot of recycled wood and spend hours removing nails before dressing, when someone recycles my stuff one day they will be able to take it straight to the saw.
Still have to work out a wedge and pin type of arrangement to secure the top.
I have been toying with some ideas, such as making some plywood out of the spotted gum and then formong it into a tenon, glueing that tenon into the table top with about 20mm sticking out, cutting a small slot into it and wedging that to the aprons somehow. Thinking out aloud.