BuckeyeDennis wrote:How long is your workpiece? When I do horizontal boring, I lock down my miter gauge to position the front end of the workpiece laterally, and I use my 520 fence to back up the other end of the workpiece. With the fence mounted on the aux table (which for rigidity should be tied to the main table with connector tubes), it can handle some fairly long workpieces. Then if you clamp stop blocks to the fence on each side of the workpiece, it ain't going anywhere.
All that said, 18" is a mighty deep hole, and drill bits tend to wander in deep holes. Especially when drilling into end grain. Immobilizing the workpiece may or may not eliminate the problem. It might also help to start the hole with a short, stiff "center drill" -- this is a common practice in metalworking.
Make a Jig or fixture for it.
You could pehaps fabricate a plywood crosscut-like table to fit in the slots, and clamp it down on extension table. Some cleats on the opposite side of the stock on that crosscut table could keep the work piece square, as well as using other recessed t-nuts and threaded rod etc to make top clamps you could bolt down. Maybe overkill for one piece, but could pay dividends in time if you have many pieces to do.
How big is the stock, what shape is the stock, and what size hole are you boring in it?
Starting that hole with the right size Forstner Bit first would give you a very true initial bore for the longer bit to follow in line to mitigate the drift.
If it is large enough hole, you might drill with Forstner all the way with a drill bit extension if it would fit inside the hole and not block cuttings.
If its a through bore, bore from both sides of the stock exactly in the same plane for 9" from each end.
A photo of what you are doing would help us envision what you are doing better.