Steel Framed Router

[JAZZCNC]

Personally I wouldn't go with 16mm at these length's unless like Jonathan you used a rotating nut setup.
They are just too close to the edge for my liking and would need to be setup and aligned absolutly perfectly and kept this way, even the slightest miss alignment at this length would show up as vibration easily creating whip as the speed rise's.

I wouldn't go with twin 25mm screws either bit OTT and hard on the motors, esp little 23's.

I see you intend using belts and pulleys so you could always go with 20mm x 5mm pitch geared 1:2. If your wanting reassurence this works good then think I've mentioned it before.? . . I have a machine that use's this setup but with a single 6nm nema 34 motor driving 2*1500mm screws joined with belts. It works very very good and cutts every thing from paper to Ali and steel with super repeatabilty and accurecy.

I will guarantee you from experience with my original 2 x 3nm setup that 2 x 4nm 23's geared 1:2 on 2005 screws will handle every thing you can thro at it,. . then some.!

Seen as your using belts and for simplicity sake my first choice from experience would be 2005 geared 1:2 but if must use 16mm or need higher rapids than 10-11mtr/min then go for the more involved rotating nut setup. . . . Both will work good.

OR find 20mm 10mm pitch screws.?