It seems I have wasted my time in building the Radford Thread Milling Attachment, making the patterns and getting them cast because they are not commercially available and spending time figuring out how to overcome the 'chicken and egg' situation of the need to hob a worm-wheel without the hob which needs the attachment to make it. It would have been far easier just to make rotary cutter with a 29 degree angle. I wish I had seen this video earlier – why can't I think of these things? Doh!