.....Using a swedge block......to help compress the billet in all directions as opposed to only vertically. ...
This will really help a lot. If you don't have one, either make one out of a block of mild steel on a milling machine, or find something with a 3/4" to 1" roundish depression down it.
If you don't have a mill, you can make a junkyard swedge tool like this:
Get a block of mild steel about 4X4X1".
Cut a 2" to 3" length of square stock that fits your anvil's hardie hole.
Drill a hole in the center of the block that the square stub will fit in. Drill it about 1/2" deep. You can grind the corners on the stub a bit if needed to make it a tight fit.
Put the stub in the hole and weld it up ( make sure it is straight). Clean up any overweld so the block can sit flush on the anvil in the hardie.
Cut a 3" to 4" piece of 1" heavy gauge pipe in half lengthwise. Schedule 80 black iron, or stainless is best.
Weld it to the top side of the block, hollow side up. Build up the welds to make them strong, and add a couple pieces of 3/8 " square stock as filler braces if needed to support the pipe sides.
Set the wire rope billet in the groove when at welding heat and hamer lightly as you turn. If you have a buddy there, have him grip the end with tongs or pliers to allow you to twist the billet tight as you set the welds. The buddy system allows a longer billet to be welded up and assures tight welds.
Don't worry about the ends welding perfect, you usually cut an inch or more off to get back to firmly welded steel.
The above hardie tool idea can be made with a piece of round stock on the top for fullering and drawing, a row of 1/4" round stock welded side by side for doing ladder pattern, a trailer hitch ball for working domed things, etc.
