This is an entirely hypothetical question as it does not apply to any current project.
When repairing dowel joints, should one re-use old dowels if they look good, or replace?
On the one hand, dowel failure occurs due to them going out of round over time, but on the other, the dowels in the furniture are perfectly acclimated.
1. Clean and re-use the old dowels.
2. Remove and replace with dowels of the same size.
3. Remove, drill for the next size up and insert a new dowel.
4. Use a Domino if you have one.
5. Burn it – anything made with dowel joinery is the work of Satan.
5, but if you like it and want to keep it 4. The ship has sailed on 1 & 2... that size dowel has already failed and the joint would be depending entirely on the glue.
#4 would seem to be the best option overall (if you have a Domino) and #3 would be second best, if you aren't weakening the parts by creating too thin of a wall around the new larger holes. If the dowels aren't glued in and you are able to remove them without chewing them up with a pliers, choose #1 over #2?
There may also be times when a few biscuits to replace the dowels are a viable solution, and more people own biscuit joiners than Dominos.
I vote #2, I typically don't like to remove any original material if I don't absolutely have to.
Also not every joint is automatically better just because you use a domino. There are reasons for using dowels, JMHO
5, 4, 2.
I HATE dowels.
There's another dowel-based option .....
In green woodworking that uses dowels, a common technique is to put the dowel into the dowel hole with the grain direction of one at right angles to the grain direction of t'other. But before you do, the dowel and it's 'ole have to be exactly sized - not to equal diameter but with the dowel very slightly larger than the 'ole.
The dowels are dried in an oven before use. And they go into the 'ole when the wood in which the hole is made is still green (i.e. damp). The dowel expands; the 'ole shrinks. They form a slight oval, with the oval of the dowel at right angles to the oval f the 'ole. This makes the 'ole grip the dowel most tenaciously!
In fact, such joinery requires no glue. The differential sizes and shapes of the dowel and it's 'ole provide so much friction that the joint won't slip.
The exact hole sizes and differentials to make depend on how big the joint is (it's nominal diameter) and the moisture difference between the wood with the 'ole and the wood making the dowel. The species of wood is also a factor.
Greenwood furniture makers typically discovered the measurement of these things by trial and error and then internalised them in the tradition. But perhaps some mathematician dendrologist has worked out a formula?
With old furniture, you could slightly enlarge the holes (which also gets rid of the old glue) then use a slightly oversize dried dowel as the repair - never the old dowel, which was already too small anyway. Put in some glue as belt & braces. The glue will also swell the dried dowel reet-quick.
I am not entirely surprised to find here so much support for 5, yet so much MCM and later furniture is doweled as it is so simple and is strong enough for the furniture to survive it's warranty period. It also allows for flat pack then local assembly with low-skill workers, keeping costs down.
This means that furniture repairs involving dowels will likely be the rule soon.
Who would have thought that the 'dowdy' mid-century furniture that was thrown out in the 80s would be so popular now? Much of that is doweled. When we come to repair what was once despised and is now a precious antique, we will have to deal with the Spawn Of Beelzebub any which way.
Personally I've found that dowel-based joinery is just like any other kind of joinery in that there's a need to understand how it works, what are the mechanics of it and how does one avoid the bad joins in favour of the good ones.
The basic issue is the roundness. Like any mortise & tenon joint, the two wooden parts making it up can be stressed in different ways, both by the usage of the furniture and by the changes in surrounding moisture. The dowel can go oval in the 'ole, which doesn't.
So, the trick is to cater to the nature of dowels and 'oles in a way that adds strength against the forces trying to crack those two joint-elements apart.
Those furniture store chairs of small cost tend to be made and put together in a cheap-as-possible way: poor materials, basic machining, too little time in assembling. Even the glue is cheap rubbish! And it's not just their dowelled chairs that fall apart, eh!
I use dowels a lot in all sorts of Arts & Craft styles of furniture. I avoid the blister packs of dowels from the hardware pound-shops and the like in favour of good quality hardwood items (usually sold in continuous lengths from a careful manufacturer) which are worth the x3 cost. Just lately I can make my own!
I drill the dowel holes with high quality drill bits of the size they're supposed to be, using a drill that doesn't wobble-open a too-big 'ole. I try for a very tight fit and use good glue in the right amounts (not much, in a good tight fit). I build things with wood that's at the moisture level (around 10-11%) that 99,99% of modern houses in the UK are at all year, courtesy of the central heating.
Add a few "tricks" such as compressing a slightly too-big dowel so it'll go in the slightly too-small 'ole then swell up again with the glue (just like with biscuits and dominoes). Pay attention to the grain direction (which should align with that of the 'ole for glued dowels, unlike with greenwood joinery dowels). Fox-wedge them if the likely stresses are needing them to be super-tight.
So far, no dowel fails. Of course, the oldest are only about 25 years old - although those early ones might have been a bit ..... not quite as good as they are now. :-)
I don't think cleaning all the old glue off (#1) is possible. If using chemicals it would be even more environmentally unsound. I'd go with #3 if necessary. If you dont have a Domino, I think Beadlock is a less expensive option. But either of those requires enough material to fit them in.
While I avoid them, I have had a situation or two, where dowels were the only feasible way to join some things.
Unless the surrounding wood is in need of repair in some way, leave it alone. Many seem to think that simply replacing a couple of dowels with a domino is going to make the joint stronger, this is naive to some degree.
Removing wood from the carcass can weaken it and is often unnecessary. Dowels are usually spaced far enough apart that a single domino won't span the gap. Creating a larger than necessary mortise in the original parts can be worse than what you started with. While a single domino by itself may be stronger than 2 sections of dowel, it all about the application that determines the strength of the entire joint, where the joint is on the piece and what stresses it is subject to. You could replace the dowels with steel rods but it won't increase the strength of the joint if the surrounding wood fails.
It;s simply not always as easy as replacing one with another
I think if you can remove it without tearing it or something up its because it already isn't working.. its shrunk over time or movement and temperature changes have caused compression and the hole is a tad larger than the dowel.
if you reinstall it it still won't be working.