I am nearing the end of my 1F rebuild, and it sounds like we have similar use cases.
I upgraded my X35 to a X50 Woodworker, caring less about speed and more about improvements to rigidity - this will need to be evaluated. I am also adding an ATC 2.2Kw spindle. I also have an aluminum extrusion table I built and a 1/2" cast aluminum plate as a top. Another difference is that I am using a different controller and also upgraded to larger steppers.
I asked myself the same question as you regarding ball screw choices - it can get complicated - and I will wait and see how my new system performs before deciding to make any changes.
Things I have considered:
The 1610 ball screw would provide 5 microns of resolution (10mm/200 SPR = 0.05mm/Step)
This compares to 0.08 for the 1616
My increasing the motor torque may help drive the 1616, providing more force at the cutter
How accurate/repeatable is the overall machine given the sum of the linear motion components used?
What if any backlash will there be? (there was little to none measured in the short time I had my X35 running)
Most steppers can only be counted on being within +/- 2 full steps (from several sources explaining the science of stepper motors). I do not plan to invest in closed loop hybrids or servos at this time.
Am I being unrealistic in my expectations of the machine I am putting together?
Will micro-stepping work to improve real-world resolution and part quality? Will the reduction of torque become an issue?
Will my work benefit from increased acceleration/velocity or resolution? Is the 1616 a good compromise, or is it intended more for the X50 application of the wider Journeyman?
Would differences in torque/forces through the ball screw have any real impact at the tool/material given appropriate feeds, speeds, chip loads, etc…?
This is why I will wait and see what happens after I start milling again. I will be sharing my recent updates soon, and will certainly share my feedback on performance in the future.
Perhaps others who have the X50, and who like us plan to use it for both aluminum and wood, will join the conversation with their experiences and recommendations.
Thank you for raising awareness and the discussion.