Friction needed in joint

[nmkloster]

This does not quite follow the guidelines because there may be a number of ways the design could go.In short, I have a 10 mm diameter part affixed to another part with a bolt. I would like some friction that allows the part to be rotated by hand and then stay in place. Just screwing it in firmly is not enough and even so I would worry that the parts would wear and loosen. Any ideas? Is it maybe just a rubber washer between the parts?

The part if you need visual reference. I've made notches that it clicks into when rotating but I would like it to adjustable down to at least 5 degree increments. It comes out too smooth if I try to do micro notches
rotpart.jpg