Something amusing to do with the Domino

[grobin]

Just for fun I tried Drawboring the loose tenons.  So far works great, but some comments:
When drilling holes they need to be perpendicular, I would recommend using a drill press.
When marking the tenon I found that running the bit in a power drill will give you a point and circle from the rad point bit.  You can just drill between the center and the outside of the circle.  (you could drill on the circle for larger pieces.
If using commercial dowels you really need a dowel plate as they tend to be very slightly over sized.
For 1/4 inch dowels in hardwoods you can sort of get by with out the drawbore pin.  But you will likely have tear out and in softwood or brittle woods it is essential.  (Two sources; Lie-Nielsen and Lee-Valley (under clamps ???).  You may have bought some at a yard sale thinking that they were weird knitting needles ;D
Use the pins on both sides.
Drawbore one end of the tenon first then the other.  I have had good success with 8 and 10mm.  6mm seems to work in some woods.
You can use the narrowest setting on the domino if you lubricate the tenon with a little beeswax mixed with mineral oil.
Eliminates faffing about with glue and worrying about open times!

I am building a test frame with construction grade pine (cheap junk) using 8mmx50 tenons and the narrowest setting without glue or drawbore and the other side with drawbore.  I am going to load one shelf a the top with about 150lbs (68kg) and let it set on my deck for a couple of months and see how it holds up.

 

[John Stevens]

I can understand why someone might want to "pin" a tenon with a dowel running through a straight hole, but I can't understand how offsetting the hole became popular.  It puts shearing force on the dowel; tension and compression on the tenon; and compression on the mortised piece...all while removing material from the tenon and the mortised piece.  As time passes and the wood expands and contracts with the seasons, some combination of the following things will happen:  (a) the dowel will deform; (b) the hole in the tenon will deform, possibly splitting the tenon; (c) the mortised piece will compress.  Whichever happens, the joint ends up looser than if the hole had not been offset.  Perhaps improved adhesives and increased labor costs are not the only reasons practice has fallen out of favor?

Regards,

John

 

[grobin]

I don't think that any of those things will happen.  But my test will tell.  Here at 9500' with very strong sun and humidity variations of as much as 20% in 12 hours it is a good accelerated aging environment.  So I will see.  There is furniture dating from around 1660 that is still in good shape that was built using this technique.

 

[mavrick1903]

Drawbores date back to green wood furniture techniques. They get tighter, not looser.

 

[ajones]

I always use draw dowels, mostly on stair parts. newel to string being a great place.

 

[John Stevens]

my test will tell.

A control group, a bigger sample size (say, a few dozen joints each) and a longer duration would make the results more convincing.

There is furniture dating from around 1660 that is still in good shape that was built using this technique.

And there's furniture from that period built with that technique that ended up in the trash centuries ago.  Perhaps the joints gave out on those pieces, or perhaps the joints were fine but they failed in other ways.  If the latter, what was the return on the extra labor cost of drawboring?

But hey, don't let me dampen your enthusiasm.  If making drawbores is something that adds value to your life, then the marginal difference in the strength of the joint--stronger or weaker--hardly matters.  Our disagreement here is similar to the perennial question of "is a floating tenon as strong as a traditional mortise and tenon?"  The answer is, "we're asking the wrong question."

Regards,

John

 

[woodguy7]

I say go for it.  I use draw boring on my staircases all the time & it gives fantastic strength to the joint & helps pull the two together.  A traditional method that has been used for hundreds of years & still being used today.  I think that says something about the quality of the technique.

Woodguy

 

[grobin]

As for loose tenon strength oddly they are stronger than conventional M&T for the same size.  I did some tests on that last year.

As I am doing destructive testing and not statistical sampling the number of joints is not really relevant.  But I will have 12 drawbored joints and 12 just tenon joints.

So far my experience is that drawbore is comparable to glue in terms of time to complete the joint.  No temperature or open time restrictions, no cleanup no waiting while the glue dries and no mucking about with clamps.  In the older furniture made with glued joints the glue usually fails after about 100 to 150 years.
BTW older common quality furnature and even some made for nobility used nails not glue.

 

[Jesse Cloud]

"But hey, don't let me dampen your enthusiasm.  If making drawbores is something that adds value to your life, then the marginal difference in the strength of the joint--stronger or weaker--hardly matters.  Our disagreement here is similar to the perennial question of "is a floating tenon as strong as a traditional mortise and tenon?"  The answer is, "we're asking the wrong question."

Regards,

John"

Well said John!

Jess

 

[grobin]

I agree it's largely a matter of taste.  But I live in a very dry climate and open time is a big problem for me.  As for which is better, I really don't care.  I am testing to see if the method is good enough for what I am building--not perfect.  So far I like it but YMMV.

 

[grobin]

BTW the more symmetric and even the pins are the better it works.  I am not a great whittler so I ordered the giant Pencil Sharpener form lee Valley (a friend has one and it makes thins a lot faster and easier).  If things keep up like this I will have as much money in Lee Valley and LN as Festool [wink]

 

[grobin]

Reasonable technique for knock down pieces as well. but you can't drive the pin out without destroying the joint (easy enough to fix if you don't glue) but driving it part way and then pulling with pliers works fine.  If you do this lubricate the pin and tenons just like you would a sliding dovetail or drawer slides.

 

[stevep]

But hey, don't let me dampen your enthusiasm.  If making drawbores is something that adds value to your life, then the marginal difference in the strength of the joint--stronger or weaker--hardly matters. 

It's nothing to do with adding value to your life. Draw boring is a traditional joinery technique that, over hundreds of years, has proved to be a good one. Most of the timber framed traditional buildings are made with pegged mortice and tenons, along with a lot of the frame and panel furniture that went inside them, and this technique was used for very good reasons:

1. Joints that are difficult or impossible to clamp, eg the stair string / newel post joint others have mentioned

2. Where glue is either not available or not going to last (which is why it was used for furniture in the days of animal glue)

3. Where the timber sizes and structures are just too big for glueing to be practical (eg timber framed houses).

4. Where a construction might need to be dismantled in the future (I think some parts of wooden carts and carriages were made to come apart for maintenance).

Traditionally the pegs were always green, and usually oak, so that they could flex as they were driven in. The offset ensures that the joint is drawn up tight and remains that way, obviating the need for glue. Of course, nowadays the joint is often used just for decoration, but there is no question that, properly done, it adds mechanical strength - it must do because it is restricting movement in the third dimension.