Thank you all for the replies, especially to mpoultan. Extension cords generally arent worth fixing unless they are 10ga or 100'; the labor and a heavy duty male plug costs more than a new 50' 12 ga cord. But a $500 chopsaw or $400 rotohammer is a different animal.
re: molded factory cords vs replacements, I usually wrap the ends with electrical tape to beef them up, regardless of if they are damaged.
The last line of that link is this:
"To satisfy the requirements of the OSHA standards, a repair would have to restore the tool to its "approved" condition in accordance with §1926.403(a). Tools ... are approved as complete factory-produced entities. The approval is for the tool as a whole - its design, capacity, materials and construction. This provision precludes the use of an approved tool if its characteristics are materially altered."
I take this to mean, as far as the cord goes, that a replacement would need to have the same # of pins of the same configuration, be wired the same polarity, use the same gauge wire, be of the same type, the same length, and attached the same way internally as the original. That's as close to a factory original as it gets short of buying a factory replacement cord, if even available.
jraef: yeah, that cord has seen better days. and that kind of thing is one reason I started this topic. A bad field repair like that is inviting an injury.