Mowing Breaking BX Blade Bolts

[logdog]

Is the thick washer with the internal hex stripped out? It should not be able to slip on the spindle -- that could wring the bolt tighter.

My washers do not have a hex, just a small curve.

 

[logdog]

I could see the bolts breaking off if someone replaced the springs with washers. Just a thought.

I cant look at those pdfs on my phone. I will check them out later. But my deck doesnt have springs. The printout the dealer gave me doesnt show any either.

 

[logdog]

Thats weird.

Ive eaten rebar with my MMM and never broke a bolt.

You sure torque is right?

Triple check that the blades arent hitting. Im wondering if there is a particularly rare situation where things line up to create contact.

The bolts arent bottoming out are they?

I use the torque listed in the owners manual and I have a good Snapon wrench. It doesnt seem the bolts are bottoming out. They are the same length as the originals.

 

[logdog]

I still have to pull the deck back off (I hate doing that) but here are a couple pics of the carnage.

 

[logdog]

Have you replaced the washers on the deck? I think the set up of the washers is supposed to allow the blades to slip on the spindle if you hit something. The washers are cupped and I think they are called a bellville spring but I could be wrong. Here are the PDFs showing the spring plate the goes between the blade bolt and the blade.
<img src="http://www.tractorbynet.com/forums/attachment.php?attachmentid=331158"/><img src="http://www.tractorbynet.com/forums/attachment.php?attachmentid=331159"/>

I figured out how to look at the pdfs and I see we were talking about the same thing.

 

[dodge man]

double post.

 

[dodge man]

My questions is how are you getting the broken bolt out of the spindle, I'd think that would be a *****. Mine does have a hex looking washer thing and I think I have two of the spring washers, but I also have a 60" deck.

 

[coveredbridge]

I have over 600 hrs on my 48" mmm with the original bolts and washers. Have never had a problem and the blades have been removed every 25 - 35 hrs for sharpening. The washers are supposed to be installed with the cupped side toward the blade. Is it possible that one or both of the washers are not installed correctly? Also, is it the same spindle position that the bolt is breaking on? Maybe those washers need replaced.

 

[SPYDERLK]

My washers do not have a hex, just a small curve.

I cant look at those pdfs on my phone. I will check them out later. But my deck doesnt have springs. The printout the dealer gave me doesnt show any either.


View attachment 331189

My questions is how are you getting the broken bolt out of the spindle, I'd think that would be a *****. Mine does have a hex looking washer thing and I think I have two of the spring washers, but I also have a 60" deck.

Those cupped washers are the spring refered to. The washer with internal hex goes under them against the blade. This washer engages a hex on the end of the spindle and prevents any blade slippage from trying to rotate the bolt tighter. Evidently the 48" mmm does not employ this because they havnt had problems - but maybe you are having problems due to this lacked feature. Incremental slippage of your blade could continue tightening the bolt til it snapped. Maybe the whole thing has happened because your bolts are easier to turn than they were and easier than they are supposed to be. Maybe the dealer sprayed some good lube into the spindle threads and its effect lingers. Try a very spare application of moly antisieze just under your bolt head and back off~5% on your torque spec to ensure that the lower friction doesnt cause overtensioning. If indeed the bolt has been being tightened to failure by the slipping blade this should stop it.

 

[radioman]

I am not sure why you are breaking the bolts, other then the cupped washer might be out of spring shape. I use a impact on mine to remove and install. I dont torque them , just go by the feel and its been over 7 years for 3 blade bolts.