I am using a swing arm for my home made device.
It was inspired by the swing arm lamp like this one
http://www.lightspc.com/img/g-2518.jpg

My swing arm is made of 3/8 square steel tubes and Delrin plates. Tubes are
attached to Delrin plates by 10-32 bolts.
I use steel washers against Delrin. That should give me low friction.

The problem I have is that it's hard to control bolts tightness. If it's not
tight enough the whole swing arm has a significant "play"
If you tight it to much it's hard to move due to high friction.

Is there a good solution for this problem?

BTW: what should I use to make sure bolts are not getting loose? Retainer
nuts, lock washers, jamming nuts?

Thanks,
Alex