I always enjoy seeing how someone has gone about making a rifle part - especially one that is not available commercially - so I'm going to start this thread by showing the process I'm following to build a tang sight to replicate (as near as photos can bring me) the tang sight that Sam Hawken added to his pistol grip target rifles.
I started with the tang already fully inlet into the wrist, so welding on a block of steel didn't seem to me to be the logical way to go about this, and Sam brazed his on, so why re-invent the wheel, so to speak. I cut a length of 1/2" mild steel bar according to the length I gleaned from research photos. The tang is curved in two directions, and I could have filed a flat onto the tang and silver soldered on the bar, and that may have been the way in which Sam did his. But where's the challenge? So I cut a curve into the base to match the tang's double curvature, using a 1 1/2" cut-off disc in a Dremel rotary tool, scrapers, and inletting black. Once the curve matched the tang, I cleaned both up well, fluxed everything, clamped the two pieces together and silver soldered it into a unit.
Once I had the sides filed down to the edges of the tang (delicate work, since the tang was already inlet and I couldn't remove any metal from the tang itself), I put the tang back into the rifle, clamped a straight edge to the top of the barrel, and drew a line parallel onto the tang block. I used a hack saw to remove the extra steel, and used a level to square the top with the barrel. Then I marked the centre and punched it, mounted the gun into the drill press vise again using a level to get it perfectly square with the world, and drilled a pilot hole right through including the stock. It came out perfectly.
Then it was only a matter of filing away all the steel that was not to be part of the base. It is 'polished' to 180 grit abrasive at this time.