Some bushhogs rotate their blades one way, some another, all regardless of PTO. Check at a large supplier and you can find hundreds of blade types. If not careful you can get a blade just like yours with same hole, angles, wings, length, width, but with the cutting edge on the wrong side.
If you have doubts for any reason (previous owner or other well-intended party) contact manufacturer for part number and diagram of what your blade SHOULD look like and compare.
I've seen blades mounted upside down, backwards, too short, trimmed with torch, sharpened incorrectly, attached with plain bolts not keyed, 'correct' but cutting edge backwards for rotation. Have become very suspicious of bargain brushhogs.
Believe it or not blades bend fairly easily and last year managed to break one. That was exciting for a few seconds. Blade life depends on use. When you have them off to sharpen compare one to another or to a new set that you keep on hand for spares and you'll see deformation over time.
Depending on intended use and your machine I suggest a disk-type stump-jumper instead of a bar for mounting blades. Get a bar-type wrapped up around a sapling and it'll turn the tractor sideways in a heartbeat--or stall or break something.
Get proper wrench for nut and remove blades annually or as needed to put in vise and sharpen with hand-grinder. Use new lockwashers each time. Watch the key on the bolt for wear. Thread sealant on bolt will allow easier future removal.
Check gearbox frequently while new until seals wear-in and top off with mfg's suggested gear oil type.
May I add an aspect regarding shear pins?
If yours has the grooved swedge-type pin get that thing out of there before it shears. It'll be a hard fight to get that inner sheared segment out of the inner rotating portion of the driveline or U-joint collar. Honest, if you have to remove a sheared swedged pin in the dark...
I have come to dislike the choose-a-length shear pins that have ten different cotter key holes because I think they shear too easily.
Here's what we use: two choices depending how you want to live life. Be aware that some driveline shear-pin holes are apparently metric or oddly sized so you may need to experiment to find the fit you desire.
(1) Use the correct size slip-fit or lightly hammered 'pin' but use a "no-grade" (Grade 2, no markings on head) bolt with the length selected such that the nut when tight shoulders up to the shank of the bolt leaving no threads to ride inside the hole thereby preventing thread-caused burrs around the hole. Use self-locking NyLock nuts. Flat washers optional but I don't like leaving scrap metal slung all around the place. When you buy a handful of the correct length bolts take a hand-grinder and make a couple of passes down the shank creating one long flat spot along the shank. I do this to better see where the pin actually is as I rotate the shaft to get holes in alignment and also to get a lube down along the sheared pin before drifting it out.
(2) Go one size smaller bolt (example: 7/16" instead of 1/2" 'pin') same as above and stay with Grade 2 head markings. The slight difference in diameter compares favorably to yield approximately the same shear requirement and makes it oh so much easier to replace the bolt. I can't recommend it but have tried one-size smaller bolt using a Grade 5 bolt and honestly can't tell much difference.
Stock a few of the correct size shear pins for future use.
Never use Grade-8 / SAE / other hardened bolts as you need the ability to shear when overloaded in order to protect both machines.
We use a 6-footer to clean up around fence-rows after haying, on pond dams, and to keep brush down through some rough goat-like pasture along tree-lines and manage to shear a pin probably two or three times a year by being fairly careful. But it doesn't take but one 'new' frost heave rock or clump of something when set too low to cost you a pin. Be prepared.
