Kubota Front Mount Snowblower: Check Shear Pins!

[boustany]

In a reply to an earlier post, I commented that I had broken the drive chain on my 60" Kubota front mount snowblower twice upon encountering a softball sized rock.

The chain is a 60H and not exactly particularly fragile. It isn't supposed to break. I went to an industrial hardware store and picked up some 60H chain, some master links, and a chain breaker. In both instsances, I was able to drive out the broken link with the chain breaker, and just replaced the bad link with a master link (so now I had 3 master links). It'll do till summer.

In any event, in the prior post I joked that maybe somebody had put a Grade 5 bolt as a shear pin. and I'd check it when it warmed up.

It was a joke. Ha ha.

It turned out THERE WAS A GRADE 5 BOLT! /forums/images/graemlins/mad.gif

The bolt was sort of 1/4 sheared so it was real hard to get out. After about 45 minutes of trying and an equal amount of time spent pondering and swearing I got it out.

Shear pins are supposed to be inexpensive components which protect the expensive parts. Its much easier to replace a shear pin than a huge drive chain. And cheaper to.

So, I replaced it with a Grade 2. As much as I know now grade 5 is too strong, I don't yet know if Grade 2 is too weak. I am pretty sure my chain won't break, in any event.

I assume somebody at the manufacturer screwed up. Just in case, you might want to check your shear pins.

Its cheap insurance.

 

[JCA]

</font><font color="blue" class="small">( Shear pins are supposed to be inexpensive components which protect the expensive parts. )</font>

That's true...though the shear bolts for the Augur cost $12 each at the Kubota dealer. Manual says they're "special". Must be.

Jim

 

[sandyc]

I bought a few shear bolts at the dealer for a few dollars. Cheap at twice the price 'cause if they don't break then you could bust a chain or even worse, throw a shaft or screw up the tranny.
Remember to check the shear bolt for the fan as well.

I have not had to use my shear bolts yet but I have them just in case.

 

[boustany]

So, I'm correct in assuming the 'special' shear bolts are not off the shelf 5/16 x 2" Grade 5 off the shelf bolts like the ones in my unit?

 

[JCA]

</font><font color="blue" class="small">( So, I'm correct in assuming the 'special' shear bolts are not off the shelf 5/16 x 2" Grade 5 off the shelf bolts like the ones in my unit? )</font>

The "special" bolts from Kubota are gold in color, notched, and threaded only on the very end. When I tried a 5/16, it was slightly smaller than the hole, leaving a little more play than I would want. 'course that doesn't mean you shouldn't use the ones you use. If it breaks before your 'blower does, I'm sure it's fine.

Jim

 

[Junkman]

</font><font color="blue" class="small">( So, I'm correct in assuming the 'special' shear bolts are not off the shelf 5/16 x 2" Grade 5 off the shelf bolts like the ones in my unit? )</font>

Go to the www.tractorsmart.com site and pull up your snowblowers parts book. If you can't find it, send them a e mail and the will send a link back to you. Then look up the page that shows the shear bolts. It will give a part # for the bolt if it is a "special" part, and it will give the dimension and hardness if it is a standard hardware part most times. The auger on my BX2750 uses a "special" part # bolt that has a kerf cut into it. The fan shear bolt is a standard hardware part, grade 5, but for some reason it also had a part number. When it arrived, it was clearly a hardware part, not special.

 

[bxbuster]

I posted last year my experience with a standard bolt. Let me just say the outcome was a non pleasant experience replacing the left hand auger. It appeared to be a fairly simple job that turned into a project from ****. Anyway, buy the shear bolts or pay the price. it's just that simple.

 

[boustany]

Good point, except my problems started because the (apparently) wrong part was installed at the factory (its painted orange and everything).

My house and property is still a work in process and it'll be a few years until the 250 or so yards of driveway are completely clean of rocks and debris and the effects of construction and landscaping.

So I'll be going through a lot of shear pins. I know now that a Grade 5 bolt as shear pin causes me a damaged chain, which is a pain in the patoot, but not a complete disaster.

Hopefully a Grade 2 won't be too soft and break all the time ...

 

[boustany]

Just as a follow up.

The parts manual give the bolt as a 5/16 x 1 3/4" Grade 5 Part # 70060-04440

So, it calls for a Grade 5, but has a Kubota product code (vs. 'Obtain Locally' for all the other off the shelf nuts and bolts).

In any event, its quite clear to me the bolt should shear before the chain breaks, so, I'd call this a design problem.

I'd suggest that if you have a Kubota front mount blower such as my L2174A, you downgrade the shear bolt strength.

 

[Junkman]

There is a second shear bolt that should protect the auger that should have broken first unless the rock was past the auger when the jam occurred. That is part number 70060-04441. If you have the incorrect part in that location, then the force would be transmitted to the fan shear bolt, which in your case was the wrong part number also. Check this other bolt to make sure that it is the correct part. There might have been more than one incorrect bolt in the system right from the factory.