Daz,
What you need- and I mean NEED is a copy of George Thomas's Model Engineers Workshop Manual. If you can rustle up more cash, get a copy of Sparey's The Amateurs Lathe and perhaps GHT's Workshop Techniques.
You desperately need the ability to make good boring tools and understand how they work. Despite ALL this prattle about carbide 'doo dahs' bought from a shop, there is NO substitute for a set of little tools made up on a home grinder out of- old hexagon keys or bike spokes or something 'equally exotic'
Where you probably went wrong is not giving enough side relief on your now broken tool which jammed against the outside bit of the cut in the hustle bustle of swarf and crap. Again, you might have had the wrong tool height- which alters the cutting geometry of your tool.
Having written all this, might I remind you that you have more than most 'big' items but now need to make those nice little items that do the work.
George Thomas rightly mentioned that 'if you didn't have the proper little bit at the cutting end'-- well, read on.
Let us know if I have it right, please! You'll enjoy the progress.