Sturdy and Fast all Steel CNC , my first build

[JAZZCNC]

Vass you cannot just rely on the Key you will need Grub screws as well to stop the pulleys coming off the shaft. You can buy pulleys with larger Boss so can get more screws in but also not uncommon to put the screws thru the teeth and provided they are below the teeth and deburred correctly it's not a problem.

Regards the servo's the rated Continous speed will probably be 3000rpm which is the Max speed they will provide continous rated torque but in practice they often will reach higher speeds at lower torque 4 or 5K is not uncommon.
Really thou you don't want to go past the rated speed/torque esp with a heavy gantry so your calcs are correct but with 3:1 ratio and 750W servos's you'll have much more torque than you need so won't be a problem within reason.
To be honest you could go lower on the ratio and increase the speed and lower inertia slightly at same time. Like I said in emails the critical speed isn't critical and you can run above it without any issues so 2010 run at 2:1 would give 1500rpm and 15mtr/min rapids which is more than enough. You won't be running above critical speed all the time and infact rarely will be for more than 2-3s at a time so it never becomes an issue. My own machine as been running 2005 screws with 1:2 ratio so double speed and well above the critical speed for 6-7yrs without any issues.
I would only use 2020 screws if the screw length was long and needed to lower screw speed to resist whip. In this case I'd go with 3:1 ratio to increase torque and make up for lower mechanical advantage from larger pitch.