Monkey Mark, sorry, I'm a bit late into this thread. I'd agree with all the excellent advice and tips given above, but would add a couple of items I've not seen mentioned so far (sorry, No. 1 is completely obvious, but still sometimes overlooked):
1. Are the bolts holding the tool into the lathe tool holder tight?
2. Your set up looks OK to me, but just to be on the safe side, especially if the steel you're turning is a bit hard, if possible I'd shift the work piece a bit deeper into the chuck - yes, I can see the shoulder you're machining, but provided you rotate the job by hand once you've re set the work piece in the chuck (to ensure nothing fouls), AND if using self-act, watch it like a hawk at the end of each saddle run, you'll be fine with the work piece a lot deeper into the chuck. Makes it much more rigid.
3. That looks like a carbide tipped tool to me. Remember that they were originally made for industrial efficiency, so can take a lot bigger (deeper) cut than an HSS tool cutting the same size & type of material can. The converse of that is that the tipped tool will often produce a lousy finish (worse than in your pic) if made to take a cut which is too fine. The trouble with a deep cut if you're trying for a nice finish is that it will expose any lack of rigidity in your whole set up (hence my comments 1 & 2 above, and someone talking about gib strips above).
If you're not sure about the gib strips (there should be 2 under each of the top slide, cross slide, and carriage/saddle), first of all grab hold of each slide/saddle in turn and see if you can move it in any direction. If you can see any movement at all, even very slight, then the relevant gib strip needs adjusting. You're looking for a couple of small bolts, probably cap head screws, each together with a lock nut. Once you've found them, slacken off the lock nuts and tighten each bolt EQUALLY until the handle which moves the relevant saddle/slide becomes very stiff to turn. Then slacken each off about a quarter turn and try the "grab test" and the "stiff handle test" again until the saddle/slide doesn't move one little jot when you grab it with all your strength and try to move it - whilst at the same time you can still turn the relevant handle comfortably without feeling any stiffness anywhere within several full rotations. This will most probably take several attempts - damhikt! (But you do get quicker with practice, I promise)!
In short Mark, you've almost certainly got some chatter somewhere in your set up and that is the arch enemy of a fine finish. All the ideas and suggestions above will enable you to get rid of all (or at least the vast majority) of the chatter. As you're not used to turning metal but do turn wood, please remember that the forces we're dealing with here are generally speaking MUCH greater than when turning wood, and even the smallest unwanted movement between the tip of the cutting tool and the work piece (much less than a thou) can cause great problems with getting the fine finish that you're looking for.
HTH, good luck.
AES
