Mini lathe - my first attempt turning plastic - useless!

[HankMcSpank]

Thanks for the prompt responses, I've just nipped up to take some pics (these are simulations as I'd thrown the part in the bin, but just retrieved it & remounted it to give you a flavour)

Firstly, this is an unfettered part that I want to turn a groove into (still in situ on an old printer)...



ok, here's the cutting tool I was trying to use...

(my suspicion is now that it's too large which means the cutting tip is too far above the centre of the plastic part.)

The following is not a good photo, but I was trying to show where the cutting tip aligns when approaching cuting the part...




this last photo is a 'rough up' of what I'm trying top achieve... actually that groove you see was done with a dremel & cutting disc as the lathe turned!




I reckon the following 'areas of investigation' can be ruled out...

1. Tool is completely sharp (it's a previously unused carbide tipped tool)

2. Motor direction ...I have the option of forward & reverse - I tried both directions!

Having pondered this a little bit more...I'm leaning towards that the tools may be a little large for my lathe's toolpost - they do fit in the tool post ok, but even to my untrained eye the tip of the tool is perhaps a little high (& probably the plastic part is being more 'ground' by the long downward edge of the cutting tool as opposed to being 'cut' by the tool tip!) . Like I say, I'm a complete 'wet behind the ears' with lathes...but hey, we've all got to start somewhere...& I started with plastic & ended up here!