I need your advice about making a wheel pommel for my sword. It's quite easy milling a wheel pommel but I have no idea how to make the hole for the tang, for it has a trapezoidal shape. I want a single-piece pommel and filing the hole to a tight fit might be a problem.
I'm seriously thinking about lost-wax casting. I would make the pommel from wax, drill a hole through then forcing it to the slightly heated tang to take it's shape. I don't want bras or bronze, silver is too expensive... I know a dentist who might have the needed equipment but they never cast iron or steel fore some unknown reason. Any suggestions?

Drill press and files/dremel.

If you posess the necessary equipment - i.e. access to the forge or oxyacetilene torch and hammers/chissels you can heat the pommel and make the hole by chisseling it out - or drill the hole and then use the chissel made to the form of the tang to give it correct form.

Well, looks like I have to make it the hard way :)

I started making my first and last pommel this way. It will be a disc pommel made from a 50 mm iron rod, 50 mm in diameter with a 29 mm thickness. I have to file out the hole for the trapezoidal tang 50 mm long 7x12 mm on one side and 7x9 mm on the other. I managed to drill a 7 mm hole than I took some files and a few hours of hard work. Now it's almost finished, but I have to tell you, there must be some better method, because this is very frustrating. It's hard to keep those lines straight, not to mention sweat and blisters and loosing God's favor :)

If I were to try this, I would use a drift in the shape of the tang? Drill a hole in the pommel, heat it up nice and red, pound it on to the drift slowly. Repeat with the drift until desired hole is done. I guess I might try to do this before milling to shape. Tis is just a guess, I haven't tried it.

I find it much easier to drill the pommel with a bit just large enough to fit the tang (no matter the tang's actual shape) and file out a small section of the hole at the bottom of the pommel to fit close enough to the tang that the pommel can't turn. There's no law requiring that the section of the pommel hole has to match the section of the tang, and I'm not sure what would be the benefit of that, anyway, as long as the pommel can't turn.

If it's any help, here's how Albion makes theirs: http://www.albion-swords.com/swords-components.htm

It shows how they use lost wax casting for their hilts, then they use grinding, sanding, and polishing to make it look all nice and shiny. There's also a lot of other steps too. Check it out, and I hope this is of some help to you. :D

I know about this method, but I ran into some difficulties. At Albion, they work with pinpoint accuracy, they make the blades on CNC milling-machines with great precision. I think they have a few pommel templates for every different tang.
You can carve out the pommel from wax, drill a hole through than you can force it to the slightly heated tang. Now, after adding some wax sticks for the vents you can embed it in plaster. After the plaster solidifies put the mold in an oven to let the wax melt and pour out. Now you have a perfect 3D negative of your piece.
I did some lost wax casting in the past using lead. Lead has a low melting point and great density and eliminates air bubbles. Lead is not good for pommel, well it's heavy but very soft and very toxic too. For less dense materials this method works only with centrifuge or vacuum machine to eliminate those bubbles and defects.
Dentist and jewelers have the necessary equipment, but I'm not sure if they can work with this amount of material (250-300 g + 50-100 g). They melt gold, silver even nickel but they never work with steel for some unknown reason. Maybe steel (besides the high melting point) has some nasty properties that makes it inadequate for precision casting?
I know a little foundry where they cast bras and bronze, but again they don't work with steel... I prefer mild steel over bras or bronze.

I heard about another method called spark milling or electro-erosion. They make the shape of the tang from a piece of graphitethen submerge the pommel in water. The high current will cause sparks and the piece of graphite will slowly penetrate the steel. This is expensive and high-tech, but it's a good idea if you know someone working in such facility wishing to get some extra drinks at the local pub. Unfortunately now in my town most of the factories are closed, but in the past communist era you could get anything for a beer or two.