I start with a piece of copper plate flattened to a size of 1/8 inch thick for tanto and a bit thicker for katana. I cut a piece of the plate oversized for the final dimensions of the habaki. Better to have extra than to fall short. I begin by putting a bend in the center with a hammer and a jig.
Then with a cross-pean hammer put a taper to the ends.
One way to make the U-shape is to mount the copper plate on a vise between steel plates.
I already forgot the most important part of all: ANNEALING. Copper is made softer by heating to "red hot" and allowing to cool in the air or quenching in water. Copper is harden by hammering or working with it. So as often as you deem it necessary anneal the copper to soften it.
Clean up the inside surfaces with a file or grinder since after the second fold it will be much harder to get in there.
Then take it to the vise again and position it between steel plates so that you can hammer the second fold into a U-shape.
A jig or punch and die combo made for the purpose of making the U-shape will speed up the process.
I use a scrap piece of steel of the approximate width of the sword's nakago as a punch to make the inside curve into a square and then it goes for a test fit on the blade.
The notch for the mune machi will be filed or cut with a jewler's saw.
Then cut off the excess copper at the bottom.
Here is a look at what we've got so far.
Now comes the easiest part by far, it is called the MACHIGANE. Whoever invented this little contraption to make it all fit together should have been invited to test the sharpness of the edge of the sword for which that habaki was made. It will take me sometimes an hour or more of fooling around with this little copper piece to get the right fit.
When looking at this picture recently it occurred to me that I used to leave the habaki's walls very thick prior to soldering. These days the habaki I make are much closer to the final shape and thickness at this point in the process. That helps when is time to hard-soldering the habaki.
This is an old picture and shows the machigane to be "inside" the habaki walls. These days my machigane "sticks out" of the habaki at the bottom at the time of soldering. These little changes are natural adjustments that occur over time when I realize that things can be improved from my old ways. I am self-taught so practice makes for a better job over time, most of the time.
Let the habaki cool down in the air then pickle the flux and now we have a rough shaped habaki.
Start working on it with files or a grinder and get it closer to your final desired shape.
I sometimes use machinist marking ink and a pointer to trace the final contour.
Then it is time for more grinding, filing, sanding and detailing to get to the final product.
I use hard silver solder for making these fittings. The strength of the bond created by the hard silver solder seems necessary for pieces like these. Once the habaki or the fuchi or kashira is constructed using the techniques described above or variations of those techniques you can texture it or carve it or patinate it.