>> lol, I just re-read this -- the first time I thought it said you were going to use a grater on some bark chips, not on the whole tree!
You laugh (and should) but I've thoguht of doing that on some of the big bark chunks I have from bags of mulch and "orchid bark". The only thing that stopped me from trying it was remembering how I grated my knuckles and fingertips when I tried to grate cheese.
I might whittle on those big bark chunks with a knife or chisel, but those cheese graters are treacherous! ;-)
I priced "food processors" and Waring blendors at Goodwill, but they're too expensive for grinding bark, even at Goodwill. A lawn mower used as a chipper-shredder would be too dirty for making seed-starting mix.
Instead, I use bark mulch pieces that are too large for seed starting, in potting mix. Wood, and bark chunks that are too big for pots, I use as mulch in raised beds.
Corey