Landing gear knee joint

Paul, its a spanner nut, typical to the style of MS172321. You can get specialty sockets from mcmaster carr (similar to their p/n 5510N119, check the size to be sure). Like everyone else I'd prefer to waste 4 hours of my time machining and grinding than paying $200, so I made my own tool.

I had the same problem on my Alon A2, had resorted to buying a lever operated grease gun with which I strong armed some grease into that trailing gear joint.
On the circular nut, it reminded me of my youth on the farm because on of my daily chores after milking cows was to separate the cream, then wash the separator before breakfast. The multiple discs in the centrifuge were held together with a nut very similar to the one retaining pin in that joint. I used a simple tool for loosening that nut twice a day. Cheers,

I had the opportunity yesterday to remove the main landing gear knee joint bolt (pin). The joint wasn’t accepting any grease so it seemed like a good idea to disassemble it and find the issue. I’m pretty sure it was just really old grease hardened in the zerk fitting channel because after cleaning it out and reassembling the grease flowed just fine. 
But, my question here is why is the pin nut of such a peculiar design? Look it up on Univair website          www.univair.com/ercoupe/view-all/f33201-...knee-joint-lock-nut/     and you’ll see what a strange piece it is.
I get that it has very fine threads (probably for fine adjustments, though there is no way that tightening the nut would help squeeze the knee joint any tighter) but why is it in a conical shape ( it doesn’t fit into any similar shaped recess) and who would have the proper tool ( not Vise Grips or a water pump plier) to properly adjust it? 
I’m about to make my own tool for the job but before I reinvent the wheel I though I’d ask if there was any knowledge about this oddity.  
Thanks,
Paul Z