Search:

If you don't need continous movement for more than 3 axis, you can make separate programs for each a-axe position. In most cases you have 4*90°
so the different programs are not really difficult to...

It seems, you need an analogue control Unit like the CSMIO IP/A or you can change the servodrives to new parts which can controlled via Step/dir.
The last possibility will be cheaper, because you...

Here are Collets similiar to ER fitting in P+C routers.
http://www.precisebits.com/products/equipment/porter-cable_0429_kits.asp?tsPT=!!!Porter-Cable_0429!!!Kit!!!PG!!!

No not replacing, the existing spindle remains still in place, but you have a special toolholder with ballbearings in it and a small beltdriven spindle in the middle of the holder, like in some older...