Wobblycogs CNC Mk2

[JAZZCNC]

I'm tempted to follow Jazz and use bearings and penny washers

Nothing wrong with Bearing and penny washers they've been working fine for 6yrs now.!! . . . . That bit of string for a belt won't work thou. .

Ok so first don't go with 1605 and 2:1 ratio it's not need and you'll want more speed than that.
Direct 1:1 will be enough for cutting aluminium. If you want to go 1:2 then buy 1610 then you'll get same resolution and 1:1 speed has 1605 but double the torque of motors so lots of torque while cutting at low speeds. You'll rarely cut above 1500mm/min in aluminium.
With 1:2 ratio on 1610 then it's a simple switch of pulley if you want speed for routing, plastics etc.

Next the frame is no where near strong enough for cutting aluminium. Beef up the lower portion, I'd suggest an outer frame with inner cross braces. Really those corner angle brackets are rubbish so I'd think about some good strong plates with plenty of bolts.

If your going vertical then you'll need to think about the gantry, Z axis has depending on which way you orientate it will depend on how chips collect on surfaces etc. You'll certainly be wanting to put covers on Z axis and belts to help stop chips collecting if your putting belts at top.
It's like this Aluminium chips fly every where and they go up before coming down so just think about what they will land on and or were could collect.
In general it's not a problem more of an annoyance because on my machine the Z axis front plate faces down and if doing again I'd face up and put cover on because the chips collect on rear of front plate. Basicly Z axis is on wrong side of gantry facing down, I'd put on top side facing up.

Hope this helps.