Darren,
Parting off is the thorn in the side of most model engineers.
In industry, if you can't do it, you are out of the door, it is classed as a normal turning job.
Stew has raised some good points, I will add a couple more.
Even if you have a QCTP, never trust it when it comes to parting off. A holder can put the tip of the cutter out of position by a couple of thou. That is enough to cause you major headaches. Always check your tool height before parting off, use the six inch rule trick. If anything the tip should be spot on or very slightly above centreline. If it is even a couple of thou low, the cutting pressures will push it even further down and the tip will usually be snapped off.
Don't play about with it, give it plenty of coolant (if you have it) or squirt some out of a squeezy bottle, and give it a fair speed and push the tip in. As soon as you stop feeding, it is a pig to get cutting again, and that is when jams and breakages occur.
I normally power feed up to mild steel hardness running at least 650 RPM. Any harder, like stainless, and I hand feed, but still at the same sort of rate, and 'feel' how the cut is going, the swarf should be coming off in nice thin ribbons.
Rigidity is paramount to parting off, and your gibs need to be tweaked up fairly tight.
When you come over, remind me, and I will give you a few instructional tips and get you to 'feel' what you are doing.
John