Quote Originally Posted by JoeHarris View Post
I went for 2005 in the end, the larger dia will hopefully help with whipping and I am going to gear it 2:1 so as to get faster feed rates
Not really, you'll end up worse than with 1610 regardless of the drive. Critical speed is proportional to the diameter, so going from 16 to 20 means the ballscrew can rotate 25% faster. However to get the same feedrate with 5mm pitch (2005), you need to spin the screw 100% faster, but can only go 25% faster... so you end up with 62.5% of the feedrate attainable with 1610.

If the L-shape gantry is reinforced by putting some box section on the back at 45° to make triangles it will be very strong.