My second router design

[Jonathan]

Ross what exactly do you mean by make the Y axis wider? doesn't this mean that the distance between the cutting tool and the back of the Y axis will be further?

Ross means increase the spacing of the Y-axis bearings. The deflection due to the bearings is proportional to the cutting force squared, so increasing them a small amount makes a surprisingly large difference.

As for the 2:1 belts, I had considered this but I wasn't sure if they would flex to much as in my old machine the belts stretched quite a lot under load. I was wondering what your experience of this was.

When the belts are used to drive the ballscrew the error due to belt stretch will, in most cases, be negligible compared to other errors. The difference with your other machine is the belt drives the axis directly, so the cutting force is applied directly to the belt. When driving a ballscrew however, the cutting force is divided by the effective ratio of the ballscrew drive, which put simply is a big number so the belt doesn't stretch much at all.

And could I ask what sort of feet rate is possible from a 5mm pitch screw using 72V NEMA 23 drivers.

Try this.