Kevin the grey said:
Are there tricks and techniques to batonning firewood into kindling or larger logs into firewood ?
It isn't tricks as much as understanding that you are trying to split the wood and not cut it and thus you have to chose splitting points which make this possible. If the grain is straight and clear it doesn't matter much and all you have to do is go either directly perpendicular or parallel to the grain, but when the grain turns, or knots, or worse yet, forks, then it starts to be difficult.
The main thing to avoid is trying to force a split perpendicular to a knot because the knot will act just like a nail and hold the wood together. If there are multiple knots then you either have to start a split inbetween them, or cleave one of the knots directly, which one depends on how the other knots run and the ability to cut through the knot itself.
There are some woods that simply won't be split easily even with steel wedges and a maul, and it doesn't need to be very big either, 8-12" is easily large enough to be a lot of problems if the wood is bad and it can often be more productive to see if there isn't easier wood to split from both a time and effort point of view.
How about splitting a seven inch diameter hardwood tree trunk into halves and quarters ?
Generally it is far easier to make the secondary splits, the primary one is the deal breaker. It is also far easier to split smaller (shorter) rounds, so if you have a saw and the wood looks bad then cut the rounds really short. Even though it can run more sawing time you will save a lot on the splitting time and really heavy splitting can be really physically demanding.
What are the practical limits to batonning with a small blade ?
None, it just takes more time and effort the less capable your tools. I have split wood by batoning with very thin edged (0.005") blades, you just have to go
really light with the impacts. That is mainly a comparison type effort though, you would always be better off with wedges on problematic wood unless you can hit the knife really hard.
There are also a lot of differences in small knives, a 1/16" blade and a 3/16" blade have little in common method wise. You can hammer the point in a crack with the 3/16" blade and torque on it to split the wood, this won't be productive on a much thinner blade. The thinner blade won't actually split the wood at all by direct batoning as it doesn't have the cross section to induce a wedging action so it is vastly less effective.
-Cliff