Hi, I recently got into this and have used both a modified M8 bottom tap (all the teeth on 3 of 4 flutes ground off), and more recently a standard internal insert tip threading tool Experiences described over on the ME site at
http://www.model-engineer.co.uk/foru...p?th=84198&p=6

Look for the later postings in the thread for my contribution, though lots of useful info there. There's a poster there called richardandtracy who has posted a useful application on his website to generate the g-code which I used, works very well.

The standard threading tool was from JB Cutting Tools
http://www.jbcuttingtools.com/epages...493/Categories
though it isn't listed on their website - a phone call might be in order. Usually they have the type number printed on the shank so if you're interested I can look it up when I'm back home.

John.