Snow Equipment Owning/Operating Breaking shearbolts

[dbuck]

I have a Kubota BX25D tractor, and a front mounted snowblower. The snowblower breaks a crazy amount of fan shear bolts every time I use it. I am using the proper ones. yesterday I was just clearing about 8 inches of powder snow, and it was breaking them for no reason. No stones rocks debris, and not even pushing it hard. Any ideas?

 

[jix]

Well, most will disagree with me, but I do not use shear bolts per se, I buy cheap grade standard economy bolts, which are made of soft metal. They will break, but not easily. IMO shear bolts are too weak for normal loads. You increase the risk of machine damage, but you do not have to change 'em every half hour, which is a PIA. It is a judgement call.

 

[leonz]

I agree with jix on this completely as the shear bolts break too easily
and changing them while laying on a tarp is *&^%$%^&*
(even with a salamander running flat out to stay warm).
I use the grade five bolts in my JD 42 inch snow caster
for my JDLA115

Many folks simply use a hack saw to cut in the regular bolts
to make them more breakable.

Having shear bolts for a walk behind is another issue as
anything can be in the snow.

 

[Toyboy]

Which fan bolt? I was breaking mine until it was told to me the long bolt that secured the fan to the shaft is grade 8. The short one that connects the flange is the soft one.

 

[dsmiley]

I have a Kubota BX25D tractor, and a front mounted snowblower. The snowblower breaks a crazy amount of fan shear bolts every time I use it. I am using the proper ones. yesterday I was just clearing about 8 inches of powder snow, and it was breaking them for no reason. No stones rocks debris, and not even pushing it hard. Any ideas?

Two questions - Are you idling when you engage the PTO and are you blowing at wide open throttle? If you are using the proper shear bolts and are not picking up anything but snow, these are the two things that come to mind.

 

[dbuck]

Well, most will disagree with me, but I do not use shear bolts per se, I buy cheap grade standard economy bolts, which are made of soft metal. They will break, but not easily. IMO shear bolts are too weak for normal loads. You increase the risk of machine damage, but you do not have to change 'em every half hour, which is a PIA. It is a judgement call.

Thanks Jix, I am going to give them a try.

 

[dbuck]

Two questions - Are you idling when you engage the PTO and are you blowing at wide open throttle? If you are using the proper shear bolts and are not picking up anything but snow, these are the two things that come to mind.

Yes I idle when turning on the PTO, and then run full throttle when blowing. RPM is around 3200 roughly, maybe a little more.

 

[dbuck]

Which fan bolt? I was breaking mine until it was told to me the long bolt that secured the fan to the shaft is grade 8. The short one that connects the flange is the soft one.

The snowblower is the Kubota 2750D, and the fan shearbolts are the proper gold coloured ones, are 5/16, part number 70060-02808. I rarely break the auger shear bolt.

 

[dsmiley]

The snowblower is the Kubota 2750D, and the fan shearbolts are the proper gold coloured ones, are 5/16, part number 70060-02808. I rarely break the auger shear bolt.

I run the same setup on my BX25. The first year I sheared 6 fan bolts but I blow nothing but graveled areas and I was picking up a lot of rocks because of the inadequate skids. I added skid shoes and made them to long enough to reach the cutting edge and now I might shear one a year or none.



Skids mounted -

 

[dbuck]

I run the same setup on my BX25. The first year I sheared 6 fan bolts but I blow nothing but graveled areas and I was picking up a lot of rocks because of the inadequate skids. I added skid shoes and made them to long enough to reach the cutting edge and now I might shear one a year or none.

View attachment 405379

Skids mounted -
View attachment 405380

That looks like a good idea. The stock ones are a bit inadequate now that you mention it. Thanks very much.

 

[DHD]

I am guessing your shear bolts are grade 8 and they have a grove cut in the shank of the bolt where that are suppose to break.

I agree with jix about using a cheap grade bolt.
I've even gone with cheap bolts that had threads the full bolt length, so when the bolt broke it would break at a thread part of the bolt rather than at an unthreaded part.
Thinking that the cut of the threads would make the bolt slightly weaker compared to a bolt that is only threaded partially up the bolt shank.
Most carriage bolts I've seen are threaded full length, and I've used carriage bolt for shear bolts, and yes they will break.
Problem with a carriage bolt is that the head of the bolt is round and requires a pair of pliers to grip the head rather than a wrench.
I buy my cheap carriage bolts by the pound at TractorSupplyCompany. I believe they are grade 5.
.

 

[dbuck]

I am guessing your shear bolts are grade 8 and they have a grove cut in the shank of the bolt where that are suppose to break.

I agree with jix about using a cheap grade bolt.
I've even gone with cheap bolts that had threads the full bolt length, so when the bolt broke it would break at a thread part of the bolt rather than at an unthreaded part.
Thinking that the cut of the threads would make the bolt slightly weaker compared to a bolt that is only threaded partially up the bolt shank.
Most carriage bolts I've seen are threaded full length, and I've used carriage bolt for shear bolts, and yes they will break.
Problem with a carriage bolt is that the head of the bolt is round and requires a pair of pliers to grip the head rather than a wrench.
I buy my cheap carriage bolts by the pound at TractorSupplyCompany. I believe they are grade 5.
.

Any reason you wouldn't use a hex bolt? That's what I'm going to try.

 

[lencamp]

My Lorenz 630 3pt blower uses (2) 1/4-20 Grade 5 full thread shear bolts on the PTO drive flange and auger chain sprockets. On a gravel road I break several during the season but nothing else has broken. Easy and cheap.

 

[dsmiley]

That looks like a good idea. The stock ones are a bit inadequate now that you mention it. Thanks very much.

You should also read this thread before using something other than OEM shear bolts. RAD, the Canadian company that built the BX2750D blower did the R&D on the bolts but there are those who think they have a better idea, and who knows, maybe they do, but personally, I don't think you can beat the OEM shear bolts.

 

[jix]

I Use3/4 inch 1/4-20 grade three crap bolts with a hex head and a plain hex nut without a washer. I use a ratchet to torque them up to about 30 Ft Lbs, WHICH SLIGHTLY OVER STRETCHES THEM AND WEAKENS THEM A BIT, so they are sure to break fairly easily. My answer, works for me.

 

[dsmiley]

I Use3/4 inch 1/4-20 grade three crap bolts with a hex head and a plain hex nut without a washer. I use a ratchet to torque them up to about 30 Ft Lbs, WHICH SLIGHTLY OVER STRETCHES THEM AND WEAKENS THEM A BIT, so they are sure to break fairly easily. My answer, works for me.

I think it will be grade 2, 5, or 8. Not grade 3.

 

[DHD]

Any reason you wouldn't use a hex bolt? That's what I'm going to try.

I haven't had much luck in finding fully threaded Grade Five 5/16" hex bolt .
That's why I was using the fully threaded carriage bolts.

 

[dbuck]

Ok so tonight I tried a regular 5/16 hex bolt, and it broke even quicker than the proper shear bolt. Totally frustrated. Taking it to my dealer tomorrow to have them assess things. Maybe there is another reason.

 

[Phil48]

Not normal...

2011 , first year I had my new front snow blower, 5 or 6 shear bolts in a nick of time! The dealer could send a competent mechanic. He isolated one by one every potential source of the problem. He found out a crooked shaft. He swamped the problematic piece on another snow blower, since then, not a single shear bolt was deheaded! There must be something a little off in your setup. Something over tight? Offset?

 

[bigtiller]

Ok so tonight I tried a regular 5/16 hex bolt, and it broke even quicker than the proper shear bolt. Totally frustrated. Taking it to my dealer tomorrow to have them assess things. Maybe there is another reason.

Try an 8mm bolt. It should fit and it is just a hair bigger.