This is a Damen CNC developed product. The problem with most trapezium nuts is that they have backlash. This design incorporates a feature which allows the backlash to be tuned out using a split nut with metric fine thread. The backlash is therefore adjustable. With the correct setting found an m3 locking bolt is used to secure the counter thread...
The nut that goes with the spindle. It does have backlash. We use the Anti Backlashnut in most machines. In some cases this round/trapezium nut is used. To elminate backlash you would need 2 nuts, that are under pretension.