Good idea. The thread on the end is metric coarse M2.5 x 0.45 I don’t know if there is a Nylock nut that tiny but you could always epoxy or permanent Loctite a nut on the end then grind or file it round, I’m not sure that the rod needs a slot on the end to tighten it. Finger tight seems to be fine.
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Fred, for R Community Bikes. www.rcommunitybikes.org
2,500 (yes 2,500) bikes given EACH YEAR to the needy 2011- 2018. All volunteer.