I got a glimpse of a shop made tool recently. I think, but am definitely not sure, that it's called a slot mortiser. I have a bench top hollow chisel mortiser -- this tool is not that.
Let me describe it.
The guy built a waist high table. Mounted a motor under it which drives a pulley which drive and axle which has a drill chuck in it. The drill chuck had a long bit in it -- I've been told it's an arbor bit which cuts in _and_ sideways.
Now along side the table were some bars whch ran vertically and horizonally in both x and y. A small platform was somehow mounted in the bars. The platform holds the wood to be mortised. The table goes into the drill and then slides left right with respect to the bit.
I DAGS and found a router based device at (http://www.woodcentral.com/shots/shot390.shtml ) but it doesn't look the same.
I will be able to view it next Tuesday night but my curiousity is killing me. I hope one of you might be able to help before next Tuesday.