I'm getting some end train tear out turning bowls. Most recently I turned a piece of Bhilwara but the problem is on multiple species so it's almost certainly a question of skill.
I finish with a NRS. At this point it seems like the key things are: stay sharp, light passes. Any other guidance here?
Also, I find that sanding with the lathe running does not improve the situation. I have to manually spot sand those areas, chasing a grain direction as I do. Am I pressing too hard? Would dampening the wood to soften fibers help? Shellac?
Thanks for any wisdom you can share.
I'm still newer to this, been turning on and off for the better part of five years, but I had a couple of years there where I turned very little. So my experience level is well below most here who often have decades of experience.
Just to offer some thoughts from my own journey here, learning what works and what does not to help with tearout.
1. Sharpness. Critical. I sharpen almost obsessively now. First, sharpen before starting, every time. Just make it a matter of habit. I clean up the edge, make sure the wings are how I need them, angle is correct, deepen or add a secondary grind on the heel to make sure I have clearance, etc. If the gouge moves through the wood like it was butter, good. When I feel like I'm just starting to have to use some force to push the gouge through the wood, then I'll give it a quick resharpen. Less than 30 seconds each, shouldn't take long to freshen up that edge. Thanks to
@John K Jordan who sent me his old 600 grit grinding wheel, my gouges are sharper than they have ever been. I used to use an 80 grit and 350 grit set of CBN wheels. I now have the 80 and 600. I've learned not all CBN wheels are created the same, and the wheel John sent is just superior. Its old, but it was a gift, and it probably needs replacing soon. I'll be buying the same (IIRC Woodturners Wonders Mega Square, although John can correct me if I am wrong):
This wheel is for customers who are not concerned about having a radius edge, it offers more flat area on both the surface and sides than any of our other wheels. The wheel edge is covered with CBN material and is a full 1.5 inches wide and 8-inches in diameter. The side faces are a full 1-inch...
woodturnerswonders.com
There is something about the nature of his wheel, even though it is 600 grit, it just grinds better, faster, and leaves me with a much sharper and more effective edge. This wheel is also wider, my older wheels were 1" wide this is 1.5" and that extra widths is extremely useful. If you don't have one of these, IMO, it is well worth the investment (as are the self-balancing washer sets, you'll want those if you don't already use CBN wheels.) Sharp! If your gouge just glides through the wood, you'll have far fewer issues with tearout. Some woods...this alone won't eliminate it, but it will help a lot.
2. Gouge design. For the outside of most of my bowls now, I use a 40/40 grind. This requires a bit of a different approach to grinding, I follow Steven Batty's approach, even bought his angle setting jig. I actually need a new platform (the ones I have all have grooves, which makes grinding the 40/40 more challenging), but once you've done it a few times it is a strait forward process. Previously I used an irish/ellseworth grind, where you have those swept back wings, for all my bowl turning. I used to have tremendous problems with tearout. I had a 40/40 grind gouge, which over time, eventually became another swept back grind, mainly because I didn't know how to properly grind a 40/40. I decided to REALLY LEARN now to do it properly, consistently, and keep the grind at the right angles. Now that I'm back to using the 40/40, it really has been a game changer for me, and has largely eliminated tearout. Combined with the very sharp edge, it is usually only on really punky wood or woods that are just innately prone to tearout, that I have any more problems. Sometimes I do still get tearout, hard to 100% eliminate, but even when I do, the depth is far, far shallower, and it is far easier to clean up with more careful cutting.
So, if you are not doing either of these, I would start. If you do use CBN wheels, it is worth looking at getting one of the 600 grit Mega Square CBN wheels from WW. A couple caveats here though...the higher grit wheel is great for M42 or other types of harder steel. For M2 steel, or softer metals, it is apparently not as good. The 350grit is wheel is better. Most tools these days are at least HSS M2, a lot are M42 or 10V or cryo or something like that and should be fine with the 600 grit. It might be worth getting a 40/40 grind gouge with harder steel, so you can both attain and keep that ultra sharp edge for longer. If you are using M2 steel, I'd say its worth considering an upgrade. Most of my tools are M42, from Carter and Son, although I have some others that are Crown Cryo, and 10V is good as well. When I go back to M2 steel, I'm always surprised at how quickly the edge degrades and I'm back to forcing the tool through the wood, ripping and shredding fibers as I go.
Of the two things above, IMO the 40/40 grind, will give you better results initially with reducing tearout, so if you cannot afford a CBN wheel setup right now, and do not currently have a 40/40 grind tool (10V or M42 metal specifically), then IMO the best thing you could do is buy one, learn how to turn with it, and hopefully rejoyce at much lower (or no!) tearout.
