Thread: Strong dowel joints?

Depends very much on the sectional size of the tenon. In chair construction, a dowel joint will invariably fail before a mortise and tenon joint. Failure is usually by fracture of the dowels, a common occurrence in cheap chairs.
I realise the OP was refering to a table rather than a chair, but I use the analogy as a chair is probably one of the most aggressive pieces of furniture when it comes to joint flex.
I make and also repair a lot ofchairs. The two most common problems are glue and or joint failure. In the case of the mortised and tenon chair it is usually just glue failure or mortise crack. When it is a fracture you can almost bet on a dowel joint. After 50 years in the trade I have seen it happen time after time. To the extent that I would no sooner put dowels in a piece of furniture than fly in the air.

I agree re chairs.
I did prototypes for the new big house in Canberra to Aldo’s design and used mortise and tenon joints.
When construction started the Joint house committee accepted dowel construction as it was cheaper.
A few years later the architects were chasing me re all the chair joint failures.
I asked if any of the small quantity chairs which were made to the original design had failed, none had.
These were made by individual craftspeople not mass produced.
Once furniture gets dumbed down and mass produced look out.
It doesn’t matter how good a reputation the company making it had.
The information desk in the foyer was made by a highly respected Sydney company, a few years later there were 6 to 8mm splits in the top. Made in Sydney, shipped to an air conditioned palace in Canberra with no regard to shrinkage allowed for in the construction.
Dont get me started on Architects, they think timber is plastic and they never design furniture with wood movement in mind.
H.

Dowels are only good for as long as the rail to leg end grain to side grain joint holds. If the glue joint fails its all over, and its down to two or three pencil sized bits of wood to hold things up, per joint . That's useless in a chair situation. A coffee table, if that's what your building, wont be given the same loads . Mortise and tenon is a lot better though.

Be careful about toughened glass.
Its heat treated and its quite often not straight in its plane . If thats the right way to say it.

I have done nice large mitered top coffee tables and had to fit glass to them that sits in a rebate. The toughened glass I ordered was 10mm thick so I made the rebate to let it sit in and because of it not being flat it showed up .
The Lady who I was building it for lived in a house with toughened glass panels running down the side of a staircase going to a basement . I ran my cabinet makers eye down each of those toughened pieces as well and a lot were also not flat but bowed!! To my newly found bit of Pi##ed of surprise. I had to pay for the glass twice!
If you want flat glass, and for it to fit in a rebate go laminated glass for safety.

And never rely on a glazier to cut a piece to fit your hole if its got to be spot on for good looks. Better to get the glass first and build the woodwork to what you end up with. If its .25mm out you can adjust for it .


Rob

For the "you shouldn't use dowels in chairs" mob: Corner Blocks.

Originally Posted by elanjacobs

For the "you shouldn't use dowels in chairs" mob: Corner Blocks.

They help a lot . It would be crazy not to use them because the work would be coming back for repair.
And dowels are the industry standard now, they last long enough to get away with it . Done well they can last long enough. There are cases of them leaving fine back chair legs stronger because less material is removed than for a tenon . They will never have the lasting or holding power of a tenon though in most uses where strength is needed. They are just relying on the glue to make them look good. The mortise and tenon is a better joint.

Originally Posted by clear out

I agree re chairs.
I did prototypes for the new big house in Canberra to Aldo’s design and used mortise and tenon joints.
When construction started the Joint house committee accepted dowel construction as it was cheaper.
A few years later the architects were chasing me re all the chair joint failures.
I asked if any of the small quantity chairs which were made to the original design had failed, none had.
These were made by individual craftspeople not mass produced.
Once furniture gets dumbed down and mass produced look out.
It doesn’t matter how good a reputation the company making it had.
The information desk in the foyer was made by a highly respected Sydney company, a few years later there were 6 to 8mm splits in the top. Made in Sydney, shipped to an air conditioned palace in Canberra with no regard to shrinkage allowed for in the construction.
Dont get me started on Architects, they think timber is plastic and they never design furniture with wood movement in mind.
H.

I can tell you some interesting stories about the timber supplied for the Big House. The lack of care with moisture content was my constant complaint, but no one would listen. It was all just rush, rush, rush.

Originally Posted by elanjacobs

For the "you shouldn't use dowels in chairs" mob: Corner Blocks.

A corner block is not always an option in many chair designs. That is not to say the corner block is a bad thing. It helps greatly with rigidity. None the less, a mortise and tenon will still outperform a dowel joint in almost every case.
The difference between quality and budget furniture is determined by several factors: Design, material, finish, craftsmanship, price and longevity.
The most important factor to the purchaser is value for money. Each purchaser has a different take on value. The budget shopper is price driven, if it looks good and is cheap we will take it. The purchaser who is not concerned or limited by budget has the luxury of taking into consideration all the factors. It is easy for the manufacturer to imitate design, material and finish. But when it comes to craftsmanship and longevity the goal posts become a little closer together.
I understand that in general business one must meet the market, but it is nice to be able to select the standard of work you wish to do and that comes with reputation.