Andy
I left the column full height so that the majority of the forces are on the lower bearing.
No, I didnt modify the drill head in any way.
The real issue with rigidity, as far as I can see, is the lower bracket which is a simple adaptation of the original drill table clamp. The bracket is much longer than it needs to be and would be better if it was shorter, the clearance required to the column is only the radius of the cutters to be used. However I made it that long to line up with the drill spindle.
What would be better would be to make two rigid brackets (shorter of course) and use two spur gears to drive it with the drill. That would improve rigidity and reverse the rotation of the cutter shaft which would make feeding easier.
As it stands, the thing I would like to improve most is the convenience of feeding at a slow and steady rate.
BTW, I have since trimmed the corners off that bit of ugly angle iron on the lower bracket!
