a similar line of thought is presented in the standards for design of timber frame structures. here's what they say:
"3.4.8 Edge Distance, End Distance and Spacing
NDS© provisions for edge distance, end distance and spacing in wood connections with dowel-
type fasteners are based upon the use of steel fasteners. Since a wood peg has substantially
lower lateral load capacity than a steel dowel of the same diameter, the required minimum
detailing dimensions (edge distance, end distance, and spacing) to prevent splitting in a pegged
joint are less than those for a joint with steel fasteners. One approach to selecting appropriate
end and edge distances is to proportion the joint based on the assumption that steel bolts will be
used instead of wood pegs. The bolt size is selected such that one steel bolt has the same
capacity as one wood peg used in the actual connection. Then end and edge distances are
selected based on the steel bolt diameter. Spacing between pegs should conform to the
provisions of the NDS© with no adjustment in fastener diameter. The recommended detailing
dimensions shown in Table C3A have been shown to develop the full strength of a pegged
mortise and tenon connection without splitting of the timber (see References 3 and 5)."
I still don't get the spacing requirements though. with white pine the 4D (where D=diameter of peg) requirement of spacing to the edge would make it impossible to put a 1" peg in anything less than a full 8" wide tenon- or am I missing something in this?
