gerryv
Long woodworking router bits are available but expensive and hard to find.
Long end mills are available and will work in many routers if the shank is 1/4" or 1/2". They aren't as good in wood as in steel and aluminum due to being the wrong geometry in the flute and cutting edges. They do useful work in a pinch though. They will have chatter problems running at 20k+ rpm if there is any run-out in the chuck at all.
Side load flexing and chatter is common in all long cutters of any type.
In the photo, Ahren's roller trucks appear to have about 6" travel (to me) since they roll on the edges of the dark gray steel plate. Behind the vertical extrusion is the edge of a small aluminum plate (Y axis leadnut mount?) that gives the appearance of blocking vertical travel of the trucks but it doesn't do so.
Many cnc routers I have investigated have moved the router instead of moving the whole z carriage and router as one unit. The stepper or servo needs to move less dead weight that way.
With the router at the lowest position, the bottom end of the lead screw protrudes about the same amount as the router's chuck with no cutter installed. This will limit how deep into a mould the cutter can reach without interference. If the router mount is modified to physically lower the router to get more depth of reach below the lead screw the z travel is still the same as it is now.
CarveOne
CarveOne
http://www.carveonecncwoodcraft.com