Here I show the process used to make a custom head stay (otherwise known as head steady) for my Triumph. This is a '61 pre unit Triumph with a later unit top end, in an earlier '58 frame, so nothing stock works. I decided to make up a neat bracket using a couple of bungs and some steel plate.
The first step was to screw the bungs in place for mock up. I mocked it up using 5/16" hardware, but switched to 3/8" hardware and bungs for the actual bracket. I used a 3/8" counterbore bung on one side and a 3/8"-16 x 1/2" long threaded bung on the other, which sandwiched a stock cast tab on the frame. I then drew up a rough cardboard template and cut it to size to check fitment.
I was having too much fun and not taking enough photos, so next shot shows the bracket tacked in place, which I did in place on the bike. I went ahead and drilled out some round stock and cut it into thick washers for the mounts on the rocker boxes. I then used a grinder to rough-cut the shape of the bracket in question, radiusing the metal for the washers with a cut off wheel and shaping them smooth with a flap disc. I also cut the slot in the body of it so the bracket could squeeze together when tightened. Once tacked, I removed it from the bike and and welded it up. Then comes the really fun part. I ground down some of the welds with a 120 grit flap disc on an electric grinder, as well as a couple of files and some emery paper. I picked up this circle stencil at a craft store for $5, and it works great for laying out some lightening holes. I figure these lightening holes help produce another 6 hp due to reduced weight. Ok, maybe only 5 hp.The use of a stencil like that, and most importantly, taking your time and center-punching before drilling, makes the end result much nicer. It really blows when you spend a couple hours on a custom bracket and then drill the holes crooked.A drill press helps for straight holes, especially in thicker steel. A nice low speed and some cutting fluid helps as well, and makes your bits last longer. Step bits (also known as unibits) are awesome, and make for less bit changes, and also allow you to chamfer the edges of your holes super easy.The final bracket bolted in place. Nice and clean, and very stout, this should do it's job well. Some final sanding and either paint or plating and it will be totally finished.