Accurate Strong Gantry

[JAZZCNC]

I agree 100% with everything Boyan says regards spindle but it just doesn't stop at the Spindle to do this correctly.

The massive build required to cut steel correctly with acceptable accurecy and repeatabilty affects the linear motion and motors used plus many other things. (Has Boyan knows well.!!)
Wood's plastics etc need higher feeds to cut correctly so this means motors which can handle high Mass of heavy gantry and still allow higher feeds.
This will mean servos to do it correctly. Servos require high pulse counts so this means quality motion control cards and control software. The list and expense goes on and up.

Has Boyan will no doubtly be very aware of this quickly gets expensive and requires more attention to detail and selection to get it correct.
Even then there will always be a compromise in the machine some where.? One machine can't do everything to high standards without being very very expensive.

IMO you will be much better building a router that will cut everything in it's capabiltys, Ie woods,plastics etc to a high standard.
Then buy a milling machine at later date that will do and give the same high accurecy and repeatabilty with Aluminium and Steel etc.

The chances of failure or dissapointment for large machine to cut steel is very high and the extra expense trying to do so easily wasted. Much better to be realistic about this just build a strong functional router and save the money you WILL waste trying to build all round machine then put it to buying a milling machine.