Great work Hogster, Those merge collectors look awesome are they an off the shelf collector or did you weld them up?
I really enjoy TIG welding stainless. It flows so nicely and you can produce some really nice welds.
For the ends where the large diameter pipe slides over the flange you might want to add a clamp setup. If it's not clamped up tight you will find that over time the pipe will fret as it flexes up and down. The pipe end will slowly enlarge letting exhaust gasses out and leave sooty marks on your nice pipes. I'll post a pic of how I clamp mine. It's not visible from the side of the car and dead easy to make. It will also let you machine the flange OD a little smaller so the pipe slips on and off easily. Once they carbon up a bit the can be difficult to get apart.
I've recently been machining more stainless and starting to get the hang of it. You need to run slower speeds and plenty of coolant. Tungsten carbide tipped tooling helps too.
I use a
synthetic coolant these days. You buy it in a 5L container and then run it about 20:1 with water. It's way better than the old vegetable based coolants because it's not prone to growing algae and other bugs in it (If you've ever had to clean out a coolant you'll be happy about that). It also stays clear rather than going milky white like the old coolants. The advantage is you can have your workpiece bathed in coolant and still see what you're doing. It's in the tanks on the Lathe and mill but I also keep a spray bottle handy for when I'm drilling etc.
Some one told me once a little rhyme to help identify where your going wrong when turning on a lathe. Talking about the swarf coming off the work piece: "If it's blue or brown slow it down".
Keep up the good work and keep us posted with progress pics.
Cheers