Hello Clark,

A mortice could be one example of an opening that I'm meaning, so cutting it necessarily exposes end grain at the top and bottom generally and since the pathway an arch makes is longer than a straight line a pill shaped mortice degrades the wood more or exposes more end grain than a comparable rectilinear mortice. This is one reason that in Japan square pegs are preferred. In a glued joint, so certain types of furniture construction, a rectangular mortice provides more glue surface than a mortice cut by say a router or a slot borer with rounded short ends where a rounded off tenon would be inserted.

Greetings,

Don Wagstaff

Hello,

Don't know what happened to the one that got this topic going. Maybe we were just being put on, maybe it was one of those smart junk mail programs but the peg subject did get me thinking and once thought through I convinced myself to the merits of the square peg over round and so made the application in some current work.






Well, I am pretty pleased all around with the effort and find it well worth the extra time put in.

Greetings,

Don Wagstaff

I have also pondered the peg, thinking it acts both as a riving wedge, due to variable abutting surface, and a key.

Hello,

Huh? But a key is the opposite of a wedge!

Greetings,

Don

I ponder if the square peg in a true tension situation would enhance the relish to shear out easier. Due to the two sharp corners making nice starts for the relish to blow out. I picture a round hole confuses the stresses and can't find a good starting point. Or at least not two clear starting points, only one from the center of the round hole. A similar effect is seen in curves cut with an adze on the under sides of joist, spreading out the shear point, as opposed to a square reduction or even a 45.

Hi Don, a normal square key abuts force at 90 degrees but if the key is rotated 45 degrees the reaction is both as a key and a riving wedge.

Roger, I do agree.

But now we'd have to properly align a square peg hole to the proper position to act as a wedge and a key. And this square peg hole as to be cut accurately for the square peg to act as a wedge and a key.

In my opinion that would make so much more extra work.

I was once told: "there is a whole world in a single blade of grass..."

The point of using a round peg and in round hole is to secure the tenon to the mortise is quick and easy. Let's do this and be done with it.

I think we're splitting hairs here.

Jim Rogers

Tim, rather than confusing the forces, why not consider the reaction forces with a peg and a bore shape the the reaction into a 180 degree spectrum.

I agree with Jim. But for fun could our elaborate on this Roger? Rotating the square peg allows for 3 point to blow out. The two sides and the center.

I am about to cut some long tenons on the bottom of two kings, they will be wedged with half round wedges and single round hole as the keying mechanism. This will be replacing a squarish tapered wedge on the underside of the tie. Much simpler to cut all around. 2" rived peg stock split down the middle for the wedge.

I have always believed in making joinery such that pegs are unimportant beyond securing things together for raising. I know many fine carpenters use pegs for structural reasons, but I avoid this at all times. And Tim introduces part of why I do so. To reduce the tension force of entire timbers down to one or two much smaller points can create a tremendous pressure. To me it seems better to have the joinery itself designed to handle tension if need be (yes I understand there is the incident of live forces temporarily placing a compression joint into tension as well)

I have always been a big fan of peg-less joinery, believing the fewer holes you cut in the timber, the better.