Well... I guess you just called me a liar based on your first sentence.
with that, I'll be sticking you on ignore after this post. No need for personal attacks here, and I'd guess you just personally attacked QUITE A FEW people.
If someone is popping correct grade shear bolts EVERY time they start up and every few minutes in light material, they need to stop, backup and check the cause, not treat the symptom. Sticking a progressively harder pin into the shear device is treating the symptom.
The key hear is finding the cause.
if it is a solenoid engaged pto that kicks in hard, then there are things you can do to lessen the load at startup.
1, make sure the mower blades are already extended and not folded and that there is no binding in the gearbox, and also that there are no obstructions under the mower.. IE.. no blades in grass or ant mounds.. etc. perhaps raise it into open air to engage to prevent excess drag, that and extend the blades.
2, engage at slowest rpm to prevent stall. if it is a single or dual clutch setup engage pto and be in gear and as you let out the clutch, the engine will be dealing with getting the machine rolling and spinning up the pto, and not just snap the pto into operation. if it is independent, you can still do this sme trick, be in gear and get rolling as you click the pto on.. the engine power has multiple loads.
3, check the fit of the torque limiter device, whether it is a shaft and sleeve, or flange style. loose fit from sleeve to shaft will cause problems as will ovaled out holes. if the holes are ovaled, and you can't afford a new shaft and yoke, rotate them 90' and drill a new matched set of holes, offset from the first, foreward or behind the other, if possible.
I'm still mowing with the same king cutter 5' mower I bought? 16 ? ys ago. I've really only ever popped shear pins mowing over dirt mounds, either ant hills or rutted up areas from atvs from tresspassing youngsters. Have never popped one on regular 'brush media'
I have another howse 5' mower, never popped a pin on it.. used to have a 4' mower.. never popped a pin on it. Have a 6' mower, changed the pin in it when I got it as the prev owner had a harder pin in it.. now using a gr2 bolt that fits good... incedentally, that mower sets behind machines with independent pto's that while they are hyd engaged, don't have much 'feather' action. Still on same pin. My 10' and 15' mowers are on slip clutches. They have slipped backing over big dirt mounds, along with making racket that sounds like thunder... No pins to pop there.
If you are hitting obstacles and popping pins... that's not the mowers fault
if the shear protection mechanism is sloppy and you haven't fixed it, and it pops pins.. that's not the mowers fault.
lastly.. check your U joints. sloppy U joints can let the pto stub on the tractor move and take up the slack on 2 sloppy joints and not get the mower input shaft moving at all, then suddenly all the u joints run out of slack, lock up and the mower input shaft sees immediate speed without the benefit of maybee that 1/4 second of slightly slower ramp up.
I ( and likely many of us here ) can't afford to replace mowers and equipment by 2nd guessing the engineers that designed them and hom experementing with different materials.
PS.. to specifically address the statement in the above post:
the thing you should be doing different is correct the cause, not the effect.
I say all of you who say use the grade bolt specified and don't change to a higher grade are a bunch of liars. You are either lying to yourself or making a statement based on non existent experience with the problem. I would bet that none of you would stick with the grade 2 bolt if you couldn't engage the PTO without the bolt shearing or if it sheared when cutting light weeds every 5 minutes. After 30 or more bolts sheared while trying to cut 10 acres of pasture, YOU WOULD be doing something different.
Regardless of what the manufacturer states (and many of them are FOS when it comes to writing a manual)if the bolts are shearing in normal duty without the slightest stall of the engine, something is not right for a bush hog which is designed to cut large brush. These new tractors with the instant on PTO switches are not designed to work with soft pins and most manufacturers have not adjusted their manuals to accommodate the snap that happens when they engage which is equivalent to hitting a large rock with the equipment which just may case a pin to shear in normal operation.
For snowblowers and other flimsy PTO powered equipment you may not want to increase the pin strength or it could damage it when a rock of other stress caused the pin to shear but we were talking about bush hogs.
