Just have the results in hand for an auction that caught my eye - it was essentially the "chassis" of a Taig mill - base, saddle, table and column - no spindle or motor and needed at least nuts and an X-axis handle. It first showed up at a starting price of $49 - after a very useful exchange with Nick Carter, I had a number for what would be needed to turn these bare bones into a CNC ready mill with the Er16 spindle. I subtracted that number from the cost of a new unit with shipping, subtracted a "cushion" (what I was willing to risk on the unit needing more than I expected - $250 in this case), subtracted the estimated shipping and arrived at a bid which I submitted - and lost ( by almost 3X!)
But, while I was waiting for the auction to run its course, I spent some time looking and thinking about the motors and drivers that I would need.
Here's the application: ~ 3" X 6" sheet brass and aluminum - 0.030" - 0.125" thick, mostly through cuts with end mills no larger than 1/8" (I have an X2 with 3 axis DRO when I need to swing a bigger tool and, for really big drills, a 16" Walker-Turner drill press - how many are old enough to recall that name?)
So - my guess is that most of the load on the steppers will simply be moving the table with little contribution from cutting tool resistance - this is what it feels like when I am hand cranking my X2 - even at the less than optimum spindle speed, I can see the bit cutting but I can't "feel" it with these small cutters - That said, I will need to keep things snug because I need hold reasonable tolerances.
OK - the point of all this - There are a bunch of obvious choices around - Xylotex, Gecko, HobbyCNC Keiling etc (and one that I can't call to mind but saw in my wanderings - reasonably priced individual drive assemblies each of which had its own integrated fan).
I have also seen on several (auction and other) sites, some very cheap packages that typically use much smaller motors (150-175 oz/in vs the 250-280 oz/in motors found on typical packages) I have also noted the the "factory" Taig full CNC set-up uses 200 oz/in motors.
Are the larger motors (a) just right (b) overkill for my application (c) good insurance against missed steps?
In the distant past,I did a fair amount of electronic design and assembly (vacuum tube audio gear) and am leaning toward brewing my own linear power supply if I decide against one of the popular package assemblies (With a linear supply, if there is noise or ripple, I know where to look - don't really understand switching supplies)
Thanks in advance for suggestions and counsel.