Cheers guys.

Yep, going to try feeding in tangentially as opposed to crashing in to the side like that..!

Hi John - yeah, I've had a play with the Chestnut Pens app - very good it is too. I'm having a go from scratch as I'm a noob when it comes to G-Code and fancy getting my pea-brain around it a bit better. Seems to me that the main difference with how Richard's app works is that he uses full circles and increments the Z at each line, where I'm asking the machine (using 'P') to make a set number of circles while the Z moves as it's doing doing that.

Well, I've ground down a cheap M4 tap, gonna stop my procrastinations and give it a go on a bit of brass... I'm reasonably confident it won't work, but ya gotta start somewhere..!

Wal.