Whoa! Drill press mortising attachment??!? Do you want a migraine and less money????
Look at even a bench top mortiser and the handle it has on it. Now look at the big rack and pinion gears that operate the plunge. Now look at the piny handle on your DP and the tiny little rack and pinion teeth it has.
See the difference? The mortiser is built to take the punishment of shoving a 1/2" square chisel into hard maple, where your drill press is made to push a sharp spinning drill bit into wood and metal, which requires a LOT less force than the chisel will.
If you don't believe me, take a 1/2" mortise chisel and try to shove it into a 1/2" hole in a piece of maple. Take it to your DP and try to use the quill to push it in. It's basically going to require that much force with the mortising attachment too. Well, a little less, but you get my point.
Drill presses are made to drill, mortisers are made to cut mortises. They can both be used for the other purpose, but neither is going to do really well.
A MUCH better solution is to make a horizontal router table like this unit from
WoodHaven.com
And then either buy their
mortising attachment
Or make your own mortising attachment.
And better still would be their
6010HD Mortising Table, which basically turns a horizontal router table into a multi-router of sorts.
I have a shop-made horizontal router table with a mortising attachment I made, and it works awesome. Super fast and easy. Mine is similar to the basic design from WoodHaven. But I'm planning to build another table using aluminum extrusions from 80-20.com and then make my own X-Y axis mortising table using heavy-duty ball-bearing drawer slides.
Their is simply no equal when it comes to the speed of a slot mortiser, which is why pros will spend thousands on a multi-router.
It makes loose tenon joinery so fast and easy you'll wonder how you ever got along without it. And if you want to use standard tenons cut into the workpiece, it's as easy as rasping round corners on the tenons or chiseling the mortises square, which only takes about a minute of paring per mortise.