RC60-72H on b7200hstd

[johndeerebones]

I am sick and tired extracting broken blade bolts. It's always the center one. It hits nothing, even raised it to cut higher this year. Still breaks at least once, sometimes twice. Every mow. I do mow ~4 acres, however, rarely do I get even 1 acre before it breaks. I even used 10.9 bolts (hardest available locally) and still broke it. Any ideas?

 

[johndeerebones]

No Ideas? Stopped raining long enough to extract ANOTHER bolt. Aggravating to say the least...

 

[N3BP]

The only suggestion I can offer is to make sure it's being tightened to the correct torque values and all friction washes are in good shape and in the proper order. I have the 48'' version of your deck which has an identical center spindle setup and my bolt must be 30 years old at this point. See attached....

 

[Russell King]

Since it may need replacing of the bolt, I would recommend replacing all of the hardware at the same time and see if that helps.

if the blade is not a OEM blade make sure it is correct hole diameter and blade thickness is correct. The thickness should not be too important but I would verify it is reasonably correct.

 

[Dave_eng]

I am sick and tired extracting broken blade bolts. It's always the center one. It hits nothing, even raised it to cut higher this year. Still breaks at least once, sometimes twice. Every mow. I do mow ~4 acres, however, rarely do I get even 1 acre before it breaks. I even used 10.9 bolts (hardest available locally) and still broke it. Any ideas?

Could you please post a photo of broken end of the blade bolt.

When you have replaced the broken bolt, slowly rotate the blade and make certain the end of the blade stays the same distance from the underside of the mower deck.

To break a bolt repeatedly, something is wrong.
If the spindle is bent and the blade is not rotating at 90 degrees to the spindle shaft, vibration could be causing a fatigue failure. Like bending a paper clip back and forth until it snaps.
Remove a second blade and nest it with the one which keeps having the center bolt fail. I am looking for a bend or twist which would cause vibration.
Dave

 

[ob1jeeper]

No Ideas? Stopped raining long enough to extract ANOTHER bolt. Aggravating to say the least...

I believe that Dave has likely hit the nail on there head...


-- If you find the shaft is NOT bent...

1- Make sure you are NOT over-tightening the bolt.

2- If you are using the recommended torque, I would them verify that the blade/washer(s) combination is truly flat, AND/OR verify that the base mating surface to which the blade is tightened against, and the bolt is threaded into, is perpendicular to the axis of the bolt's shank.

Either of the above could result in the bolt becoming stress fractured when tightening, dramatically shortening it's life-span..

 

[johndeerebones]

Shaft isn't bent. Aftermarket blades, bolts aren't overtightened. All 3 blades nest perfectly. Pretty sure they aren't bent. I am however going to replace them due to corners rounding. Most cutting in the edge bit of blade. Cut quality suffers.