If anyone here has any experience of using some of those $200 - $500 4th axis components off eBay or some of the diy CNC stores, I'd be interested to hear what you have been able to make with them and what their limitations are?

Most people seem to mount them on their short axis in the pics I have seen. I was wondering if there is a reason for that? My interest would be in using one to make wooden rifle stocks and possibly some aluminum chassis systems. This would mean work pieces that are 20" - 30" long by 6" tall and 1.5" thick. Is there any reason you can't buy a cheap 4th axis and just mount the head and tail stock 30" apart on the long axis? Or do you need to invest more in something capable of holding longer work pieces? Are the cheap 4th axis options capable of working with aluminum?

What (if any) are some of the other diy 4th axis options? For example, has anyone converted a mini benchtop lathe to turn work pieces on their CNC router? Some of the mini metal lathes that are capable of turning steel sell for less than $500 delivered these days. They seem to be made of superior components to your average 4th axis eBay kit. Could you simple replace the lathe bed with your CNC router table and run the motor from your Gecko?