The quality of a fillet or a weld is often directly related to the quality of the prep work. For tube-to-tube construction as used in bicycle construction, this means the cleanliness of the tubes, whether or not you have drilled your vent holes, and of course, the mitering. A close miter is a thing of beauty with the tubes neatly slotting against each other and no gap between them. However, get it wrong, and you can have large gaps that become nearly impossible to bridge when welding or brazing and even if you do manage to bridge them, they leave an exceedingly ugly mark.
To miter tubes, there are the two methods that can be done in your average shop; mitering by hand or mitering by machine. Both have their benefits and drawbacks in accuracy or setup time or setup costs, but they can both get the job done. For this latest frame being built, all the tubes are being hand mitered, mostly for the experience but also for the speed with which the miters can be finished and the lack of tooling costs associated with machine fixturing. As we have only hand mitered a few frames before the miters aren’t quite as close as I would like (perfect) but they are certainly close enough to get good fillets. Will we get new tubing and try again to perfect the joint? Possibly, but only for the next frame. From here on out it’s merely a matter of finishing up the fixtures and then on to tacking it all together.