shear pin breakage

[Toby873]

Howse 6' cutter behind a Branson 4720. Broke my first shear pin due to starting the pto way too fast, second pin broke for unknown reason, now I have just sheared my third pin cutting grass, my pto is at proper speed, I am going at a good rate of speed, and I was CUTTING GRASS......I cant stand this. Any help?

 

[Toby873]

Howse 6' cutter behind a Branson 4720. Broke my first shear pin due to starting the pto way too fast, second pin broke for unknown reason, now I have just sheared my third pin cutting grass, my pto is at proper speed, I am going at a good rate of speed, and I was CUTTING GRASS......I cant stand this. Any help?

 

[BB_TX]

Not familiar with the Branson 4720. I run a Howse 6' behind a JD 950 (27 PTO HP) with no problems. I shear maybe 3 bolts a year using standard grade 2 bolts mowing pasture and occasional brush.

 

[BB_TX]

Not familiar with the Branson 4720. I run a Howse 6' behind a JD 950 (27 PTO HP) with no problems. I shear maybe 3 bolts a year using standard grade 2 bolts mowing pasture and occasional brush.

 

[InlineDieselFan]

Unless you are hitting something be it the ground, rocks, wood. This would not seem normal, are you using the proper size shear pin? I do not know Branson tractors but I asssume a 4720 is 47 HP? That would not seem to be way over powered for a 6 foot brush hog.

What rating of bolt is it?

Are the blades able to move freely, so that when you hit the thick patch of grass the blade can move.

Those would be my guesses.

steve

 

[InlineDieselFan]

Unless you are hitting something be it the ground, rocks, wood. This would not seem normal, are you using the proper size shear pin? I do not know Branson tractors but I asssume a 4720 is 47 HP? That would not seem to be way over powered for a 6 foot brush hog.

What rating of bolt is it?

Are the blades able to move freely, so that when you hit the thick patch of grass the blade can move.

Those would be my guesses.

steve

 

[KiotiJohn]

I've seen ratings for shear pins from grade 2 to grade 5 bolts. 5 seems high, but some manufacturers use them in their equipment. I would suggest, since this is happening in only grass, that your mower requires a higher grade shear pin. If you're using a 2 trying going to a 5 and see if that fixes it.

Of course, you should check the mower's manual first to see what they recommend. My Howse mower uses a grade 5.

John

 

[KiotiJohn]

I've seen ratings for shear pins from grade 2 to grade 5 bolts. 5 seems high, but some manufacturers use them in their equipment. I would suggest, since this is happening in only grass, that your mower requires a higher grade shear pin. If you're using a 2 trying going to a 5 and see if that fixes it.

Of course, you should check the mower's manual first to see what they recommend. My Howse mower uses a grade 5.

John

 

[MrSteve]

I would go with your blades are not swinging out like they should... Take a look under the cutter and see if they are "out" before hitting the PTO and if the pin breaks again, before you do anything look under the mower and see where the blades are AFTER the break.

Maybe you have your RPMs to hight when turning the PTO on?

When I got my tractor and mower the dealer right there on the lot broke a pin showing me how to turn on the PTO. Well he set the RPMs to 1100 or so when that happen. So what I have done, is turn on the PTO at idle speed and I have never broken a pin.

 

[MrSteve]

I would go with your blades are not swinging out like they should... Take a look under the cutter and see if they are "out" before hitting the PTO and if the pin breaks again, before you do anything look under the mower and see where the blades are AFTER the break.

Maybe you have your RPMs to hight when turning the PTO on?

When I got my tractor and mower the dealer right there on the lot broke a pin showing me how to turn on the PTO. Well he set the RPMs to 1100 or so when that happen. So what I have done, is turn on the PTO at idle speed and I have never broken a pin.