I looked for this particular type of modification for a benchtop drill press but couldn't find one so I went about trying to invent one on my own. The problem with small benchtop drill presses is the amount of space between the center of the drill chuck and the column. Whenever a hole is required that exceeds that spacing, one must usually rely on hand drilling.
With a caliper, I measured the diameter of the column which came to about 1.88" and began searching metal shops, electrical and plumbing supplies for piping with a similar diameter and found common black pipe at a plumbing supply store (1-1/2" pipe) with an outside diameter that came to about 1.9". Close enough.
With the piece that was to fit into the drill press head, I had to remove a little material and not having a lathe, I used a regular angle grinder to remove evenly distributed strips around the pipe as carefully as possible, checking each time I made a complete pass to see if it would fit. This was accomplished by simply placing the pipe in a vise and rotating it as required. Eventually, after six passes, the pipe fit in snugly. I also cut one threaded end off of the pipe to length for better grip of the locking keys that hold the pipe in place in the head and for good clearance under the motor.
After that, it was simply a matter of screwing the assembly together and mounting it with a flange and some 5/16" bolts to particle board base. I also used the same material to make a large 2'x18" table.
I could get the table clamp to fit on this pipe but it was very tight and moving the table up and down was next to impossible, so I reused the original column and flange and mounted it next to the new mount adding the large particle board table installed with 3/8" bolts and some hardwood runners underneath.
After assembling everything, I squared the drill chuck to the table but have not yet tried it as I just completed it late yesterday. I will begin drilling some test holes all the time watching if the chuck goes out of square and if so, will need to come up with an idea to hold the entire assembly together so that it doesn't go out of square.
As it sits, I now have 13" of clearance between the center of the chuck and the edge of the new column as opposed to the original 5" of clearance with the old column. The entire assembly appears to be very solid at this point and if it works, should improve my ability to drill nice straight holes in larger materials.
And comments or suggestions are welcome. I would especially be very interested to hear any suggestions to holding the piping assembly together so that it remains square. Thanks