grip for glass/hotbed

Grip to fit the round glass (18cm diameter) to a round hotbed (22cm diameter).
Just print 3 of them. Use a 15mm m3 screw with a washer, a small spring and a nyloc nut to fit the grip to the hotbed.

Turn the grip to hold the glass.

Rev: I've updated the heat bed cristal grip. Now it is easier to lock and unlock it thanks to the lever.
Place a washer between grip and heat bead in order to isolate it from heat. Use a small spring and a nylon nut to lock it under the aluminium plate.