PTO slip clutch - bad or?

[MHarryE]

The cutter gearbox has a power rating and the slip clutch is intended to protect that. Doesn’t mater if you have a 100 HP tractor or 30 HP, if the gearbox is rated at 75 hp the slip clutch is selected to protect that torque at 540 RPM (assuming that you don’t have a 1000 RPM mower). The Bondioli slip clutch can be configured for different torque limits depending on what capacity the OEM buying it from Bondioli wants. So the length in your manual is probably the length selected by your cutter manufacturer. However, nothing in those slip clutches is built so close that it can be dialed in precisely - tolerance on springs, tolerance on friction material, etc. Actually the person saying theirs specifies tightening finger tight, then giving specific turns is the best. Springs have a designed spring ratio, bolts have a specific thread pitch, number of turns gives the closest spring force regardless of what the initial spring length might be.

 

[Tx Jim]

Ditto I agree with MHarryE amount of horsepower of tractor has no real bearing on slip clutch adjustment but the amount of torque to power that equipment does matter.

 

[compact]

I set torque evenly to 100 inch pounds with my 31pto 3520 and a 6 bolt Single disc clutch on a frontier mower. I use a 1/4 drive torque wrench. Depending on variables like thread pitch, thread rust, number of Friction plates, pto HP, and how much PTO hp the mower will take (big tractor/ small mower) the numbers will vary. I set the mower into thick grass down low , idle the machine down as low as she goes, well below torque peak, like 700rpm, and engage the pto. It should stall (I disengage before it does) Run up to 1500 and engage for a sec, it should grunt a bit, clutch marks should show slippage when I go look. Then when I mow thick grass I値l stop and see if plates are hot, if so I tighten 20% or so and try again. Hit big object and it should slip, if not loosen 20%. After a while you will find the happy point and I write the clutch bolt torque on the side of the gear box with a paint pen. Using a torque wrench takes the guesswork out after that,