Fallon
Super Member
7' is a bastard size for rotary cutters. They are way long. This causes issues lifting them due to leverage of the weight being so far back, not to mention manuverability issues. 8' dual spindle cutters are a lot shorter, more maneuverable & often even take less HP to run. But cost a lot more.
Asking what grade to get without saying what you need to mow is asking how much wood could a woodchuck chuck... if you are just mowing grass, weeds & regularly mowed fields a light duty cutter will get the job done (if you get a quality one it will last a fair while). But if you are going to be mowing brush or woody stuff bigger than your fingers you want to make sure you get a medium duty mower. Generally medium duty will have thicker steel for the deck & a higher HP rated gearbox. Heavy duty is the same, even thicker steel & bigger gearbox. The HD cutters get really heavy, causing even more balance issues to deal with.
Light duty cutters can wear out pretty quick, but often because they are pushed past their limits. But quality ones used within their design parameters should be good value if that's your need.
A sheer pin just snaps when an excessive load occurs. A slip clutch is more or less like a car clutch that is clamped together with springs. If an excessive force is applied, it slips until the force decreases. If you are mowing gnarly stuff it slips a lot & you dont replace sheer pins every 5 minutes. But you need to do an hours maintenance on them anually.
My rotary cutter was sold to me as having a slip clutch. Went to do the first annual maintenance & found a sheer pin under the guards & was upset. But in the 3 years I owned it I spent 0 minutes on PTO safety systems. On my tiller I hate loosening up the clutch to free it up then re-tighten everything every spring. I just smoked the clutch on a tilling job & didnt have the right wrenches in the cab to tighten things up (probably wasn't set tight enough after the last maintnance).
So while a slip clutch is generally better, it does cost more & is a bigger pain in the *** if you rarely run into things with your mower blades. Dont discount a shear pin if you are just mowing pasture or field that gets mowed at least annually.
