Well, you can cut a triangular sort of piece and form it in a swage block....or I just watched a video on ganoksin where the guy formed it with his round nose pliers. The trick I think is getting the right shape to start. You want a curve on the small end, not a point.

here is an old conversation from artmetal which may help you

http://www.artmetal.com/blog/sdeloof/2007/05/how_to_make_a_cone_out_of_sheet_metal

~Janice

The first method that comes to mind is to start with a strip at least the length you want, with a tapering width to match the cross section you'd like. You could start forming it into a groove in a piece of wood. You might like to make a mandrel that would fit inside to help while you bring the edges together. A piece of hard wood might be sufficient for that. How long the tube will be and how thick the metal is will influence how you go about it.

You could roughly figure the width of the strip at any point by multiplying the diameter you want by pi, then adding about 1.5 times the thickness of the metal.

How long do you wish this horn tip to be? It might be easier to make the smooth tapered horn with a point and then after the seam is soldered.... cut off the tip to the size you desire.

A great deal will depend on how many of these are needed. If a single one is desired... then perhaps casting one solid might be the best choice.

Fred Zweig
Metalsmith

I think you want to make a spiculum. Check out http://www.ganoksin.com/borisat/nenam/anticlastic-raising.htm

marilyn

Another option would be to spin a tube down. You can control the taper any way you want. Lathe is required.

I agree that spinning that tube is probably the best way to go. I you don't have a lathe, you might be able to spin it using a drill press with some jigs made to allow you to do vertical spinning. The form you describe sounds like a flared and tapered tube, from what I gather. You want it to start at aroound 3mm diameter and taper up to about 10mm and then have a volute that flares to 15mm, right?

If you start with a 10 mm tube about 16 or 18 gauge, you can spin down the smaller end and then flare the large end by spinning against an inner mandrel to stretch the metal.