I need to drill 7/8" holes, perfectly vertical through 6x6 (5.5" depth) pressure treated beams for a retaining wall. (Don't ask - I'm already way too far in to change course!)
The ideal solution would be a drill press with a 6" throw, which I thought I had access to, but it turns out I haven't found one that can do more than about 4". (I have 6-8 holes in unique positions in each of many beams, so flipping them over to drill through from the back isn't a practical solution.)
I've built a jig to try the trick of reflecting the bit across two mirrors set at 90 degrees from each other, but it's relatively clumsy to use for holes this size and depth, and is too easy to get off course since it's all controlled by hand anyway.
Without a drill press this size, I'm likely going to use a heavy duty hand drill. I haven't been able to find a jig to physically hold it plumb when dealing with bits this size, but hope that maybe someone here knows of one, or has some other good trick!