Here is a tool to eliminate backlash form the Proxxon mf 70.
The Proxxon MF70 has just plastic Nuts and it is not possible to install
Metal ones.
One can spend a lot of money for this:
http://www.usovo.de/shop/CNC-Machines-accessories/CNC-Machine-accessories/Accessories-CNC-Machines/Proxxon-MF70CNC-accessories/Tuning-Spindle-Set-2-mm::299.html
I just cut out a hole in the Sliding Bed and mounted the
printed part.
In the printed part 2 nuts are installed an one spring.
On nut is fixed in the slot the other is just sliding in the hole.
The spring is between the two nuts.
The pressure made by the spring reduces the backlash nearly to zero.
If you did not modified the MF70 to a cnc you need two left-hand and two right hand nuts.
If you dont know how to mound it better dont do it. Its not so easy! but is a very cheap possibility to reduce backlash ;-)