Hello All,
I am wondering if there are any recommendations for a sweet spot on a Z height maximum for milling. Still keeping rigid enough to mill aluminum accurately, yet as much flexibility without losing accuracy.
What have you all build that you are happy with?
Sweet spot is as short as you can make it and still easily change bits. 
Remember most piece work depth is going to be more determined by the cut depth of the bit and most of those are really well under 50mm, if a bit has cutting area to about half of bit length then the best height for you involves 100mm or so.
Thanks Bill! So about 4 inches total.
Now how about x/y? I hear the 24"*24" a lot. Is that the working area dimension. And can a little more be added without much detriment or more in one direction? I believe unlike the lowboy additional length in either x or y is an issue?
Thanks Chris
A 24" by 24" working area works great - just make sure you use Ryan’s calculator to get the dimensions for the various pieces.
Mine ended up being a hair under 24" x 24" working area because the blade I was using the cut my conduit was just a trifle too thick. Two 10’ pieces of conduit really work efficiently when you cut them into thirds for the six X/Y tubes, then a 5’ length has more than enough to do Z and legs. If I’d tried to go bigger I’d have had to buy an extra 10’ length, if I’d built smaller I’d have had more than one piece of conduit left over.