The free wood from the tree companies here cannot be split with an axe. I even bent the 1" thick wedge trying to use a 6 way wedge on my splitter. I'm talking logs over 2 feet in diameter of hardwood. I'm not saying its impossible but you'd be working an entire weekend for a cord when I can do that in less than 2 hours with a splitter.
My mother has a saying, “can’t never did try and if it did then it didn’t try hard enough”.
All wood can be split with an axe. Some might be harder than others, so that calls for cutting it shorter so it can be split.
Oak, hedge, black locust are all hardwoods. Seems to me that 40-45 years ago a single wedge had no issue splitting wood as big as could be lifted by two guys up onto the splitter. I’ve seen 4 ft oak slid up on, rolled up on, and hoisted by machine up onto out old splitter. Never had a problem. My dad was a great mechanic and my uncle a great welder. Yeah…we tore a few wedges off. Got smarter and better on the welding and smarter with the wood.
Try cutting and splitting standing dead elm and watch the sparks fly off your saw chain. It can still be cut, the fun part is the splitting. NOT! That crap shreds rather than splits, but we still got it done. If at first you don’t succeed, try, try again. Bigger more powerful saws and splitters, sharper axes and shorter wood make for better axe splitting. If you have to split by axe, maybe let rounds sit a couple years, then split them (after they’ve dried a year or two) after they’ve frozen solid…they’ll bust right apart…same for the splitter….better welds on the wedge, more power, shorter pieces…even frozen will bust clean if they’re dry enough and short enough.
Myself, my dad, and my grandpa did this for a living 40-50 years ago. We’re weren’t the first to do it, we wasn’t the last. These days, better saws, better splitters, etc. No excuses! We didn’t have 6 way wedged then although some may have. They’re common today. Use a single wedge in wood that calls for it.