From what I've been able to determine, both the 1 and 2 piece socketed spears greatly out number the 'tanged' types. It's also interesting to note that regardless of socket type they are often not welded shut, NOR even always butted completely closed!
Anyway, I'm starting out with 1.5"x.25" 5160 spring steel. This particular piece was cut 12" long with about 8" allocated for the spear head and 4" for socket.
The first step is to taper an end to a point with the final taper profile you're after. Once this is done measure from the point back to where you want the socket to start.
Next isolate the socket area by fullering. I used a "hinge fuller" (fig 1) but in period this would have been accomplished with either a "spring fuller" (fig 2) or by placing the stock at a 45deg to the edge of the anvil and hammering straight down, flipping then repeating.
Once the area is isolated (fig 3) taper the socket from the end down to the fullered area. The fuller width should be nearly the same size as the desired final transition from blade to socket. Then using the pein on your hammer in parallel with the length of the socket widen the socket material. As the socket starts to flare it will be necessary to also hammer (with the pein) parallel to the edges. (fig 4)
Occasionally go back with the hammer face and flatten the developing ridges and valleys so they do not get too high or uneven. (fig 5)
Next start the socket curling by either centering the flare over the horn and slowly hammering off the centerline working each side evenly, OR hammering the flair into a swedge. In period this could easily have been accomplished by placing the flare on a stump and using the pein repeating the same blow placement used to flare it originally. Since it's on a wooden stump, those struck areas will burn out making a swedge (depression) on the fly. Figures 6-9 show the progression of curling the socket.
Once at this stage the curving can be completed by tapping down on the socket as it is rolled on the anvil face. (Fig 9)
Fig. 1 - Fullering spear head with a hinge fuller hardie.
Fig 3 - Fuller depressions clearly mark blade from socket.
Fig 5 - Fully fanned and smooth socket material
Fig 7 - Slow but steady progress rolling the socket
Fig 9 (Right ) - Final 'closed' socket. Some alignment issues were able to be addressed.
Fig. 2 - Spring fuller.
Fig 4 - Initial spreading of the socket.
Fig 6 - Start of rolling the socket
Fig 8 (Left) - Note that the socket is not closing up evenly. This can be caused by a couple of factors; not evenly working the curling of the socket, and/or having an imbalance of material from uneven fanning of the socket section.
Fig 10 - Completed spear 'blank' ready and awaiting edge grinding and polishing.