https://www.osha.gov/pls/oshaweb/owadis ... p_id=27353https://www.osha.gov/pls/oshaweb/owadis ... p_id=22666https://www.osha.gov/pls/oshaweb/owadis ... p_id=27356If you read through these, it becomes very obvious that OSHA certainly allows for repairs to "extension cords" and so does MSHA for that matter, but then they keep referring to "Accepted" (ie, Listed) components, and so does the NEC.
Let's take for instance one case. A molded cord set (aka "extension cord") is bought. Let's for the sake of argument assume its #12 so the limitation against repairing anything smaller does not apply. The cord itself is almost always type SJO wiring. Making a repair, even changing the ends out though, violates listing because it's a listed ASSEMBLY. If the wire and the ends were Listed individually then no problem. But modifying the original cord is not acceptable.
Let's change it up and give a real world example. Strangely enough the motion picture industry is simply not allowed to use "hard usage" (SJO) cords. They are required by Code to use extra hard usage (SO) cords. There are no premade SO cord assemblies on the market so they have to by Listed cord and Listed NEMA plugs/receptacles for use. The resulting field assembly consists of Listed components and if assembled by a qualified person, it's perfectly legal. And if a repair consists of clipping off the end and reinstalling the plug, it would still be indistinguishable from the original in any way from a new assembly.
The same thing applies to a number of "cords" used by the mining industry labelled SHD-GC, MPF, W, etc. In fact most mines have so much cable that needs to be repaired all the time that it becomes a full time position. They typically use vulcanized splices because it restores the cable back to factory original as much as possible. Otherwise with most cables there are acceptable repair procedures and you can find the procedures and references in the Electrician's Handbook. But again, it's time consuming to do a splice. Ends take about 15-20 minutes. Splices can take close to an hour. If you are repairing a mining cable with a cost of around $20-$50/foot, it's probably worth the materials and labor. But for a common molded SJO extension cord when that is equal to the price, throw it away and start over.
Whether it's mining, motion picture industry, or anyone else, field made flexible cords are common place in certain applications, and the "exception" to repairs is never going away for that reason. So it may seem like OSHA is being purposely vague or saying "yeah you can do that but not really", but that's not the case. If you make your own cords in the work place you can also repair your own cords in the work place, and there's nothing wrong with that at all, and it happens all the time. But for very practical cost reasons with rare exceptions nobody actually does that.