With some materials like aluminum and stainless, long stringers are a fact of life. While chip breakers may help, you will still get stringers with these materials. Chip breakers are not magic. In order for them to work, you need to take a heavy cut so if your lathe is not rigid enough or powerful enough to allow that then chip breakers will make little difference, at least in my experience.
I did a lot of experimentation with chip breakers at one point (in HSS and inserted carbide) and found that you need a relatively healthy depth of cut and faster feed rates to make them work. The reason for this is simple; it takes a fairly heavy chip to break. If you watch aluminum coming over the tip of a HSS tool with a chip breaker, the chips from a light cut flow right over the chip breaker; don't take my word for it, try it and see. This is especially true if the tool is ground with conventional rake angles and the user relies on the chip breaker to handle the chip.
The reason faster feed rates work better is because it causes the chip flow to be directed into the chip breaker valley, where it hits the back side of the valley of the chip breaker and has a better chance to break off. How fast is fast? Well, you have to experiment to find the right feed rate and if you power feed, that may or may not be what your gearing allows. If you want to find the right rate, feed manually.
Coolant also makes a huge difference, perhaps even more than the chip breaker itself, because it reduces temps at the point of cut and makes the chips break easier. Actually, quite often the chip will not break; it will coil. You will especially see this when boring; chips will turn from stringers into coiled chips that eject easily just by using adequate amounts of coolant, and this happens with inserts with or without chip breakers. If you're cutting aluminum with a heavy depth of cut and a fairly fast feed rate then sulfur-bearing cutting oils can make a big difference (vs something like WD-40) in the chip because it hangs around long enough to actually cool the material at the point of cut, thereby helping the chip to break/coil.
On my Sherline lathe, I found that larger amounts of side rake and back rake on my HSS tools did more for me than chip breakers. Rake improves chip flow, thereby lowering cutting temps. Add more cutting fluid than I normally use also helps. When I take a decent cut in aluminum, 0.050" to 0.065", I don't have stringers; I get coils. The same is true on my Emco lathe. When taking light finishing cuts, I still produce stringers but they are fine and not bothersome, especially if I use coolant.
I guess the bottom line, for me, is that chip breakers are not worth the time it takes to grind them. Roughing heavy, feeding faster, using coolant, and aggressive rake angles work better for me.
