I've used NRS's split ring and spring system with two washers coupled with their standard lock and 8" towers for at least a dozen years, never had an issue but it can be a pain to get the spilt ring apart at times...
This year I ditched the NRS towers (I wanted to fine tune height) and have tried two different DIY tower arrangements, one is a AAA (DRE style, different angle) and the other I stole from GC Guide, rowframe and whitewater worthy) which is a HDPE bushing drilled out to 5/8" (the diameter of most standard locks). I still use the washer/spring/washer/split ring set up with Cobra locks and have been tossing around the idea of threading the lock.
Originally Posted by rpludwig
just tell them what size of die to use so they can thread there own oar locks and what nut they need to purchase
To elaborate on the above comment:
A 5/8" die is like $11.50 at the local hardware store and it's something most anyone can do, you need a die, a vice and a wrench big enough to hold the die (or preferably a die handle, but they're expensive if this is your only use for one). To be certain of size just take the lock into the store and have them measure the diameter, find the die that fits that diameter (probably 5/8") and buy nylock nuts that match the die thread and pitch. Put the lock in the vice and carefully thread the die down, going back and forth to clear the cuttings and use some sort of oil to lube the cutting surface. Brass and Al are pretty easy to work so it should be very simple which ever lock you have. You want enough thread to grab the nylon, so usually a 1/4" or so longer than the nut.