Wobblycogs CNC Mk1

[JAZZCNC]

My advice is only build this length if you truely need it because over 1500mm your in funny territory. 16mm is too close for whip and vibration etc and has you've seen 25mm takes you to another level regards motors/drives/PSU and for no gain really.

Your Max speeds are a bit off mark thou and provided you use decent voltage you will easily get more than 4000mm/min cutting speeds. Don't get caught up in the critical speed figures has they are wide margin and in practice you can get much higher speeds provided the power is there.

I run twin 1500mm 20mm 5mm pitch geared 1:2 with 75v and 6NM 34's and can easily cut at 7mtr/min and rapid @ 11-12mtr/min. Going by the specs for a 5mm pitch screw then they are probably spinning close to twice the critical speed and have been doing for years without any trouble.
Now I'm not saying to do this has 10mm pitch is clearly better and less hassle. When I built my machine 10mm wasn't available from Chai or china and far too expensive in UK so this was my only option, But today thats not the case so go for 10mm.

Regards cutting Ali @ 1800mm/min then thats not realistic for DIY machine at any decent DOC(Really it should be removed from the sheet has it's misleading.!!) and would need a very very strong machine with a very powerful spindle. I rarely cut Ali much above 1200mm/min and 95%+ of time it's below 1K.

I you must have the length then IMO go for the 25mm/34 combo has it will give the least hassle and yes while in theory it won't quite reach the speeds 16mm Dia would allow it will still easily full-fill your needs.