If you read from post #7 on the conversation is about sch 80 steel pipe. AND YOU MAKE A COMMENT ON HOW TO CUT IT ON A TABLE SAW. Don't try to cut as you described, you'll will be injured.
He's right Don't even try it with a metal disk. Typically I don't cut pipe the long way, but if was to I would snap a straight chalk line down the pipe. Get yourself a box of heavy metal cutting wheels 4 1/2 to 5" for an angle grinder. 4 1/2" is the most common grinder guard size, I have a Hilti that takes a 5in wheel. A partner saw would work too if you can hold a straight line with it. If you can use a cutting torch and get a clean cut that would probably be the best way. I have a Milwaukee metal skill saw that works great on thick metal and doesn't throw sparks, but never tried cutting pipe the long way with it. I'm awful with a cutting torch so I would go with the grinder personally. SCH 80 pipe is some thick material, good luck!
SCH 40 is going to be the most common thickness pipe you'll find (home cheapo, lowes, etc), SCH 80 will only be found at a plumbing supply company or steel fab shop. Usually in my field it's only used with steam or high pressure piping, metal fab shops could be using it for all kinds things.
I give you guys an A for effort for using PVC, It's a cheap an easy way to test it out! I wouldn't be surprised if your tractors shattered the plastic pipe on a cold day. That stuff shatters like glass in below freezing weather by just dropping it on the ground. Don't forget there are 2 grades of PVC, DWV and PRESSURE. They are both SCH 40 but DWV has a foam core, Pressure is solid plastic. DWV is the cheapest and should have " DWV not for pressure" printed along the pipe. I would guess the the Pressure PVC would hold up a little longer. You could get SCH 80 PVC, that stuff is rugged but more expensive. CPVC would be a waste of money. Your best cheap option with plastic is with Black ABS pipe, it would be less likely to shatter. Home Depot usually carries it but depending on where you live in the country it may not even exist.
A thin wall metal pipe like conduit would probably work the best, it should last a season and it's cheap. You can just make one thin slice down it and it will be able to flex enough to fit it on. SCH 40 and 80 steel pipe will be very hard to split and slide on your buckets.