Based on the video provided by sean, pegs do nothing to add strength to a joint. I've always felt that pegs were a throwback to medieval times when timber framing technique used no glue whatsoever and pegs simply prevented slippage of the geometry of the structure, whether it was architectural or a piece of furniture.

the testing was pretty cool. this was apparently all on new pieces.

it would be interesting to see the same thing on period pieces or any piece that has aged significantly. with the movement over time, expansion and contraction, dried glue, and stress on the joints, if the peg makes any difference. i have seen a lot of period tenoned joints that have separated but i have never seen a pegged joint pull apart.

who's willing to donate a stickley chair or limbert settle for testing?

I don’t use any glue in my tenons, but I do glue my pegs in. So if I ever needed to take any apart, a frame or bed board, which I just had to do, To shorting a footboard. I just drill out the peg, and tap the hole thing apart. this has worked out great for me. as long as the mortise and tenon are well fitted no glues are needed, and no glue to clean off.
Here is some reading:
Bending moment capacity of rectangular mortise and tenon furniture joints.
From: Forest Products Journal | Date: December 1, 2005
Withdrawal capacity of pinned and unpinned round mortise and tenon furniture joints.
From: Forest Products Journal | Date: December 1, 2004 |

I pay in Iowa for Quartered White Oak, “kiln dried” to 6-7% FAS grade $4.25 to $4.50 a broad foot. Clean stock 12’ to 16’ length, Very minimum riff.

quote:

Originally posted by littledan:
By all means peg your joints- a little added insurance and definitely a mark of "Arts&Craftsmanship". Today's adhesives do seem nothing short of miraculous,but they have yet to be tested by time. My experiences have demonstrated that rived or end grain pegs are measurably stronger than a face cut dowel. As to the ebonizing question, why not use ebony (or blackwood,etc). Those pen turning blanks are mighty convenient...

Right you are. Several years ago I bought a $50 'bargain bag' of random length ebony 1x1 turning spindles to use for plugs... and I won't run out for awhile yet.

I use the ebony plugs in anything I do out of cherry or mesquite.

KC

I can say from experience that pegged tenons hold up very well over time vs. glue of any kind. I've bought many pieces of Arts & Crafts furniture with glued construction that have wobble to them whereas pegged tenons stay tight. Even if the peg loosens or cracks, you can easily make another( which I think is easier than taking a joint apart and re-gluing it!). I just bought a Roycroft Little Journeys stand, and it's tight as a drum( held together with nothing but pegged tenons and table irons to hold the top on). As for conservation: save the wood for furniture, not paper! We live in such a disposable society. Just eliminating the unnecessary packaging from most products would make a big difference.