Getting back to Don's comment about timing the threads, he says that it would 'average' 1/2 of the thread distance. When I took a work shop with Bonnie Klein, many years ago, she said it was impossible to time the threads so they would line up predictably. After thinking about it for some years, I figured out a method so that mine take about 5 minutes on the clock of adjustment to get the grain to line up. I figured it out from thinking that when I want to make repeated length cuts on the table saw or the chop saw, I used stop blocks, which is a block clamped into place so I don't have to measure each one. Applying that to box threading, in order to use a stop block, I needed a measure device. So, I line the top and bottom up with the grain matched, and put a pencil line on both top and bottom for a reference point. For the stop block, I use the ruler from a tri square, which is about 1 inch wide and about 3/32 thick. First cutting the threads on the lid, I slide the X/Y jig up to the cutter and space it the thickness of the ruler away from the cutter. The pencil line is at 12 o'clock. Cut the threads. When cutting the bottom, Same method, but I have the pencil mark at about 5 minutes before 12. Simple, and repeatable, and if you ever have to remount, as long as the pencil lines are still on, it is simple and easy and repeatable. You may have to experiment a bit to make sure it works for different thread counts, but with mine and the 16 tpi, I never have to go more than a light NRS scrape on the shoulder to get the fit right. I never try to get it perfect from the cutter and leave the adjusting for the perfect fit.
robo hippy