[axkiker]

So im a very novice hobby machinest. In fact I just purchased my first verticle knee mill a few weeks ago and am having a blast using it.

I am contemplating the buildup of some sort of cnc outfit. I dont want to retrofit my knee mill with cnc controls. I want to build up something like the cnc routers they discuss in other threads. The catch here is that I want to be able to mill aluminum. Nothing too heavy, but stock in the range of 1" thick and 1'x1' sq would be common.

MY first question is why in the world do the CNC milling machines turn so many rpms. I see them all the time running 10k plus while cutting up aluminum stock. I can cut aluminum all daylong with my mill turning 1000 rpms. So why is it better to turn so many more rpms with the cnc outfits.

Also I keep hearing people talk about the need for HUGE motors being used in cnc outfits which are made to mill alumium and other metals. Why is this the case. My mill is only 1.5 hp and does fine. Now granted it turns alot less rpms which im sure increases the TQ. However why then would the cnc mills not take the same approach. Slow down the rpms and decrease the motor size.

thanks

[ger21]

Because time is money and you can cut 10 times faster at 10K rpm as you can at 1K rpm. But you need a lot more power to cut 10 times faster.

[Geof]

And you get a much better surface finish at 10000 rpm.

I think what you should do is find some full scale machine shop(s) in your area and find out if they will show you around. They may just tell you to get lost but possibly they will be reasonable, If you want to take a trip to Vancouver, B.C., I would be happy to give you a tour and explain why it is necessary to go fast.