A general machining question if you don't mind.



Over the last three years I have completely worn out the
sherline milling machine. Over the last one year I have developed
the CNC conversion to its fullest degree on this machine. However
over three years of use the X axis ways are completely destroyed. As
well the machine is quite small for what I wish to do. So I find
myself browsing for a new machine.

Two general options come to mind: one would be a full-size
used Bridgeport milling machine, or Bridgeport clone. Which I would
slowly convert to servo based CNC controls, likely using gecko
drivers,EMC , and servo motors purchased from Ebay. The other
options is one of the Chinese benchtop milling machine's. What I do
not understand is the functional difference between a gear head
machine, versus a belt driven machine. For equivalent hp ratings
there appears to be about $300 difference between equally equipped
machines. I understand the gear head allows for more rapid spindles
speed changes but I do not understand the claims of more stable
spindle speeds. I could see if there was gross belt slippage this
would be an issue. But I do not understand in general usage how
driving the spindle by means of gears produces any more efficient
drive than the use of a belt. I understand from engineering that the
gear drive is more efficient than a belt, but very slightly so . I
could see if this were to be a CNC application where the motor was to
have an encoder. But a very slight wavering of the spindle speed
should have no functional difference in machining.

Any thoughts anyone has, especially comments from individuals
who have used both machines would be appreciated

The likely application of this machine would be making something
along the lines of go cart parts, radio control car parts or the like.