I've been trying to figure out the best way to do this for a few weeks now, and I haven't come up with anything I like yet. I'm working on a product where 4 pieces of 1/4" round aluminum need to be able to screw onto four sides of both 1 1/2" OD aluminum tube and 2" OD tube. Both tubes are .065. Picture a hat rack with the large tube being the center, but that's not what it is. These parts will be assembled by the buyer, so it has to be simple, and yes, it does have to be in separate parts... it can't be welded. Having nuts welded onto the inside of the tube would probably be best, but the tube is too long to do that. The best I can come up with is to just send a 4-40 machine screw all the way through the tube and two pieces of 1/4" at a time, and put a nut on the opposite side, but the proper lengths for the screws to do that don't seem to be standard in 4-40 size. It would be great to figure out a way to screw the rounds directly to each four sides of the center tube, but I can't think of a way to do it.
Any mechanical geniuses have a good idea?