I've worked with wood most of my life, but I'm not as experienced with metals... I recently found that I have to do a project for work that involves drilling multiple holes through both sides of 3/4"x 3/4" and1/16 thick square aluminum tube to make antennas. Imagine a TV antenna basically... There needs to be multiple matched holes along each tube, and into those holes, 1/4" solid round will be inserted through both sides. In other words, the holes on both sides of the tubing have to be aligned pretty darn well, otherwise a slight misalignment will translate to the 1/4" round being way off center by the time it gets to the end... Which is about 1-2 feet long. There will be a tad bit of wiggle room since the round will be attached by threads on the end, and a nuts on both sides of the square tube, but not a whole lot.
I had no idea this would be so difficult. I went and got a Sears 9" bench drill press and proceeded by clamping the tube into a press vise. I figured once I had it lined up and centered, I could just slide the tube down for each hole... Wrong. There seems to be no rhyme or reason to how it turns out in the end. If both holes end up being centered on both sides, it seems to be luck more then anything. There seemed to be a lot of slop in the spindle on the drill, so I took that back and tried a Ryobi... Worse. The run-out on it was so bad, I could see it with the naked eye on just a 1/8" bit. When I rotated the bit 180 degrees and made an indentation, there was almost 1/32 of an inch space between the two. Ridiculous. I can't believe there isn't even a decent small bench press available nowadays, but that's a different story.
I've tried using short bits, center punching first, not center punching, 1/16" pilot holes, a countersink for a starting point... Nothing works. I've actually had better luck just drilling with a hand drill, but that only works for the top hole... There's no chance at getting the alignment right with bottom hole by had. I tried one of those portable drill press stands, but it just wasn't precise enough. Is there some kind of a portable drill guide I could use with a bushing or something?
I'm kind of lost at this point... Am I really trying to do something that can't be done without a mill? That's hard to believe. The actual physical aspects of the holes is good... Nice and clean. It's just the alignment I seem to have a problem with. I had no idea something that seemed so simple would give me such grief. I have a lot more respect for you metal heads now. Any ideas are welcome.