I want to give tension setting a go and I've found a nice project to follow that at least *looks* do-able. However, it says to use a Hart bur 3.5mm (45 degree), and I've searched for this on the Cookson site but can't find anything that matches. I've googled it and got some US matches but I've not found anything to order from the UK. The gemstone will just be a test-friendly CZ 3.5 faceted round stone. Can anyone suggest a cookson bur that would do the job? ...and any other tension setting hints and tips would be great!