Eric,
First of all, I applaud you for striving for a cleaner cut! I've known turners who are perfectly satisfied with their method of turning rough then fixing it with the "80 grit gouge" and their work shows it. One guy said he uses 60 grit. Ack.
There are several types of "non-clean" cuts that need sanding - one is grain tearout. Tearout REALLY needs to be removed by recutting with very sharp tools and good technique, occasionally with something added to the wood first (CA glue, oil, etc.)
The other roughness is a series of ridges and troughs from poor tool control. (Curves that need to be refined can also fit here.) Besides just more practice, others have already mentioned things that help. I have a few thoughts which may or may not help but is what I do. (I often start with 320/400 paper and sometimes 600, not for bragging rights but because that's all it needs.)
- As someone mentioned, find a club, watch some demos, turn with a friend or mentor, get some honest critique of your methods. Someone else might easily spot something you could do differently and make a big difference. They could check your tool sharpness, stance, toolrest height, etc. Lots of people would be willing to help - I know I love having visitors come to play in my shop. If you find yourself in East Tenn, come visit!
- As mentioned, very sharp tools. The old saying "if you can't sharpen, you can't turn" certainly applies. Not seeing your tools I don't know if this applies but something to think of. I get my best edges using a Tormek but a fine grinding stone or CBN with the Tormek or Wolverine jigs is a close second.
- Honed edges. In addition to sharpening, I like to hone/strop the edges on a leather strap or leather wheel on the Tormek. This can make a huge difference with hard, fine-grained woods like ebony, tulipwood, and dogwood. The wood can't be smoother than the cutting edge. If the edge is polished like a mirror, the wood can be very smooth, given good tool control. I'll sometimes turn a small piece from dogwood just to show people a surface that needs no sanding.
- Spin fast and move the tool slowly. Moving the tool too fast can create ridges that must be removed. I've practiced to move the gouges very slowly - the slower, the smoother the surface can be. Several professional turners have pointed out the same thing. Cowboy-hat turner Chris Ramsey repeated this several times while demoing at our club - his control with a bowl gouge was excellent.
- On a bowl, use shear scraping to take out ridges. The wings of a bowl gouge, a spindle gouge, or a flat or curved scraper work well.
- If you haven't tried them, the Hunter carbide tools can give a very good surface.
- Light touch. As mentioned, a light touch helps a lot. I've seen turners power into hogging out bowls with a big gouge with all their strength, planning a smoother finishing cut. The worst turner I ever saw at a demo turned like this. The problem was his finishing cut wasn't much better. What I do and highly recommend is at least while refining the surface shape, make every cut a practice cut. Try to make each practice cut as smooth as possible This will certainly take longer, but by the time you do a bunch of these in a row your hands and arms and stance are ready for the money cut.
- Tool control, light touch, spindle turning. The experts (Darlow, Raffan, Penta, Clewes, etc) have said: spindle turning will teach you fine tool control and just the right touch. In a class once Jimmy Clewes came around to give each person some personal help and when I told him I was primarily a spindle turner he said oh, you won't have any trouble with this and went on to the next person. Raffan teaches spindle turning first before touching a bowl. I was told it's the same in the schools.
When I teach beginners, we start with spindles I always start them with the skew chisel - it really doesn't take long before they can handle almost any tool. People who start turning and go straight to bowls sometimes miss so much.
These two girls never touched a lathe before. After we spent on long day on spindles they made these on the second lesson, their first attempts. No power sanding needed. (These are glossy with wet oil.)
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Now for my secret weapon. Instead of sanding I reach for small cabinet scrapers. These are worthless for removing tearout (go back and make a clean cut for that) but they are perfect for any kind of ridges, the bottom of the bowl/plate/platter, inside and out. I use them at slow speed, both forward and reverse, and very often with the lathe turned off. Sometimes I'll remove the piece and sit with the scraper. I confess that once I started using these years ago I haven't used sandpaper coarse sandpaper on a bowl or platter, most often nothing coarser than 400 is needed. A friend scoffed at this claim until he came and watched, then he wanted to know where I got my scrapers! I bought some from Highland Hardware, some from Woodcraft, some online somewhere.
Just like the other tools, these scrapers must be sharpened correctly. I bought some from Highland Hardware, some from Woodcraft. They can be ground from larger flat scrapers as well. I use these in my hand in the air, unsupported. They work on green wood as well as what I mostly turn, very dry wood.
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Once I started using these scrapers I haven't even pulled my power sanding gear out of the drawer. As a huge health bonus, there are no clouds of sanding dust. Another bonus is sharp detail is easily preserved, detail that sanding will often soften.
JKJ