Article used for May and June education sessions
Principle 1: Tool Sharpness
There was some discussion on making the sharpening process quickly and accurately repeatable.
Use of a purchased jig for quickly resetting grinding angles was one suggestion
A simple hand-made set of spacers was another suggestion
Kirk Deheer article Sharpening Demystified where spacers above are explained
Principle 2: Grain Direction
The lathe is a power tool and as such it can be tempting to use that power to cut the wood without regard for the grain which usually requires coarser grits of sandpaper to remove the rough surface these techniques leave behind.
Visual aids, discussion and hands-on comparisons were used in this part of the education session in both spindle and side grain orientation.
Principle 3: Bevel Angle and Length
The common bevel angles for spindle gouges, scrapers, bowl gouges, skew chisels, etc. can be a confusing topic for the new turner. Add the amount the bevel is swept-back and how that affects the nose profile of the tool and it can all get to be too much. As in the article we used some common angles and bevel angles in our education session discussing the how-and-why behind these select few.
We did take a bit of a tanget in our discussion of why one would grind away the back-bevel to both eliminate this scarring that can be caused by this sharp surface but also to turn a tighter radiused curve with our tools.
Principle 4: Bevel Contact
People talk about floating the bevel today rather than rubbing the bevel to make sure everyone knows that too much pressure against the wood is a bad thing. Too little pressure and you increase the odds for a catch. We used a clip from a Glenn Lucas video to clearly show what part of the bevel is rubbing, great shots of all the common cuts on these DVDs.
Principle 5: Cutting Arcs
There are some who say every cut done on the lathe is either a bead or a cove. A smooth even curve in spindle or side grain orientation is always pleasing to the eye. Hands-on session used coves and beads in spindle orientation but this discussion was also covered again when we did some work on bowls.
Principle 6: Shavings
Proof of clean cutting is usually thought to be in the long curls of shavings coming off the tool. Keeping clearance so the shavings can escape the tool, taking an even and not too aggressive cut and other principles of the shavings we want when cutting cleanly were covered in this session.
Principle 7: Tool Clearance
We have all burned the surface of the wood when not providing enough tool clearance when using the parting tool. Discussion on this topic highlighted the many other situations where we often forget to have enough clearance for the tool to cut cleanly.
Principle 8: Amount of Cutting Edge Applied
A roughing cut removing a significant amount of wood in one pass is a prime example of a very aggressive cut, a cut which cannot be considered to be clean. Going to a smaller gouge is one trick we all use to take a finer, cleaner finishing cut. We discussed easing the final profiling cuts with our larger tools, taking a less aggressive cut engaging a much smaller percentage of the cutting edge as another way to be aware of the amount of cutting edge applied to cut more cleanly.
Principle 9: Feed Rate
The suggestion that we should let the wood come to the tool is a way of suggesting that too fast of a feed rate is going to roughen your cut. Even a sharp tool will rip at the wood if pushed too fast. Very little debate on this one.
Principle 10: Tool Stability
Needing to have 5 inches of tool handle leverage for every one inch that the tool hung off the tool rest was news to some. It is hard to defend this suggested rule since it ignores the diameter or thickness of the tool itself. Working examples of smaller versus larger gouges make it obvious that on this topic you need to know your tool, your wood and your capabilities.
If you are getting a poor cut with a sharp tool, especially if you are getting vibration, consider how stable your cutting edge is.