Dowel or Blind M & T?

[custard]

The question what’s the strongest, dowel or M&T, is a pointless red herring. The fact is that for domestic furniture in almost every case they’re both plenty strong enough. It’s like asking if a Porsche is faster than a Ferrari when all you need is a car for the daily commute.

A second reason why it’s a meaningless question is that there’s a massive difference between a joint’s potential strength, and it’s actual strength when executed by the average wood butcher.

Just because lab experiments reveal one joint is stronger than the other means nothing if you personally don’t have the skill to consistently execute the joint to that level.

It’s worth remembering that a piece of furniture is only as strong as it’s weakest joint. So if your dowel joints consistently have strength X, but your M&T joints vary from 0.5X to 2X (not an unrealistic scenario), then you’d still produce a stronger piece of furniture by using weaker dowel joints.

 

[user22161]

There's nothing wrong with dowel joints, but a problem you may well encounter is sourcing good enough quality dowels to make a decent dowel joint.

How many make their own dowels?

Me. With a dowel plate. It's very handy and ensures that your dowel peg is straight grained.
But trad dowels were usually just riven roughly square (much easier than round ones, and straight grained)) hammered into round drilled holes (much easier than square ones).

I think I'll either make or buy a dowel plate as, each time I buy some, there's a slight size variation. My own thoughts are that dowels are fine but not in load bearing joints such as chair leg attachment.

 

[woodbloke66]

The question what’s the strongest, dowel or M&T, is a pointless red herring. The fact is that for domestic furniture in almost every case they’re both plenty strong enough. It’s like asking if a Porsche is faster than a Ferrari when all you need is a car for the daily commute.

A second reason why it’s a meaningless question is that there’s a massive difference between a joint’s potential strength, and it’s actual strength when executed by the average wood butcher.

Just because lab experiments reveal one joint is stronger than the other means nothing if you personally don’t have the skill to consistently execute the joint to that level.

It’s worth remembering that a piece of furniture is only as strong as it’s weakest joint. So if your dowel joints consistently have strength X, but your M&T joints vary from 0.5X to 2X (not an unrealistic scenario), then you’d still produce a stronger piece of furniture by using weaker dowel joints.

All of the above points that Custard makes are absolutely spot on, but purely for interests sake, these clips are worth watching in sequence and are the original videos done by the inventor of the Dowelmax system. Having briefly spent five minutes trying to wade through 200 odd back issues of F&C, I gave up, but then I wondered whether the wonders of t'interweb could provide enlightenment. There are more videos but these three compare the dowel joint to the m/t when tested to destruction; in one test the wood failed before the dowel joint - Rob

1.https://www.youtube.com/watch?v=8CPecqPhg0k
2. https://www.youtube.com/watch?v=lES-zekLhqU
3. https://www.youtube.com/watch?v=fTw0IVUEHgA

 

[Jacob]

Bought dowels are no good for strength- they are machined and will not follow the grain if it goes off a bit.
Dowel plate dowels can only follow the grain or they split. They also have a roughish surface and be slightly less than dead straight, both good for glue holding.

Rob's theory doesn't alter the proven systematic observation over many years that in actual real use in place of M&Ts dowels are prone to failure. We will never know whether or not they were correctly made joints.

 

[woodbloke66]

We will never know whether or not they were correctly made joints.

Agreed Jacob and that's not actually shown in the clips. We can assume that the dowel joints were made correctly but whether or not the m/t were made to the same standard is a moot point. Suffice to say that it's an interesting set of videos and convinced me that a properly made dowel joint isn't the 'poor relation' or 'also ran' that I once thought it was - Rob

 

[MikeG.]

We will never know whether or not they were correctly made joints.

Agreed Jacob and that's not actually shown in the clips. We can assume that the dowel joints were made correctly but whether or not the m/t were made to the same standard is a moot point. Suffice to say that it's an interesting set of videos and convinced me that a properly made dowel joint isn't the 'poor relation' or 'also ran' that I once thought it was - Rob

And yet I presume you watched the other video linked to here, and weren't convinced. Why would you believe one test in one video, but not give equal weight to another test in another video? I suspect you might have fallen for 'seeing what you want to see'.

 

[Just4Fun]

The question what’s the strongest, dowel or M&T, is a pointless red herring. The fact is that for domestic furniture in almost every case they’re both plenty strong enough.

I agree with this but I don't think it is particularly important or relevant. Asking which joint is stronger in any particular situation is not (IMHO) a red herring because:

1. Your "almost" highlights the fact that sometimes this isn't true. There are projects where strength takes on a greater importance and for those projects choosing the most appropriate joint is important.
Think about a typical shelf unit from Ikea where the shelves are supported on those little plastic clips inserted into small holes in chipboard. They are almost always strong enough but would you use them if you were putting heavy weights like car gearboxes on the shelf? Or if you were putting rare and expensive Ming vases on the shelf and the cost of a shelf failure could be huge? What would you do in such a situation if you did not know of a better solution?

2. If M&T are stronger than dowels I could feel justified in using them most of the time in order to develop the skill of making M&T joints so that when I really do need one I am able to make a good one. If dowel joints are stronger I could throw out my horse hair shirt, avoid the extra time & effort needed to make M&T joints and use dowels every time.

3. Sometimes enquiring minds just want to know. OK, so it makes no difference 99% of the time but I still want to do the best job I can on all my projects.

4. Knowing that joint A is stronger does not stop me using joint B where it is good enough for the project.

 

[woodbloke66]

And yet I presume you watched the other video linked to here, and weren't convinced. Why would you believe one test in one video, but not give equal weight to another test in another video? I suspect you might have fallen for 'seeing what you want to see'.

Another interesting clip Mike, but it's not 'like' for 'like' as far as the dowel joints are concerned. The Dowelmax joint had four dowels (stated at the beginning) in each case, the guy building the school chairs only used two widely spaced dowels for his test piece. I would say that in the latter case, the joint wasn't properly constructed, which has been the thrust of the discussion all along. Two extra dowels closely spaced together (which is what the Dowelmax jig does) makes a big difference - Rob

 

[Inspector]

I used to work a little for my father in his refinishing business. Most of what they did was repair and refinish furniture brought over from the UK by the container load for the local auction houses. Every type of joinery fails eventually. Chairs made with dowel and M&T failed in the same way. Usually because the glue had let go. Those that broke were from joints that were, because of design small, crests to chair legs for instance, where the leg top split or the crest rail broke in the short grain and sometimes the dowel would break. A tenon would have too because they would have had to be just as small to fit but didn't come made that way very often. Most chairs were just loose and we pulled them apart and reglued them and they were solid again. Ready for decades more butts at the dinner table.

The one nice thing about a dowel plate is that if you make them with a number of over and undersized holes you get to make a dowel that fits a hole exactly. More important repairing old work than new but handy never the less.

Pete

 

[Phil Pascoe]

I re glued ten bar stools that fell apart when six months or so old - they were dowelled and had been glued with some sort of UF . I glued them with PVA and they were eventually throw out twenty years later without their having been touched again. Because my boss was a dork who wouldn't return a load of chairs when one broke at three days old I ended repairing a hundred and fifty when the tenons broke off - the aprons (I believe this is the correct name) were solid, curved and cut from a solid and every single rear side tenon broke. These would have been better dowelled. Not good, but better.