Snow Equipment Owning/Operating FarmKing Buhler 740 Snow Blower

[pitt_md]

I used my blower for the first time this year and broke my first shear pin/bolt.
The manual calls for a 5/16" shear bolt. The hole on my 740 only takes a 1/4" bolt max. Funny thing is the unit came with a couple of spare 5/16" shear bolts. I was able to run the blower fine with a 1/4" replacement but was just wondering if it should really have a 5/16" bolt?

 

[Craig Clayton]

The grade of your shear pin is the problem. As the manual calls for a 5/16 and your pin is drilled for 1/4 stay with that size. Put in a better grade of bolt, a bolt with no markings on the head is a grade ( 2 ) , a triangle or three marks is a grade ( 5 ) , five marks is a grade ( 8 ). Select a long shank bolt so the entire soild unthreaded part is in the yoke. Shim with washers to get the perfect fit. Just remember as you go up in grade the bolts are stronger so move up with caution.
Thats what I did with mine, and on my bench sits a small container of ( Snow blower shear pins ).
Craig Clayton

 

[pitt_md]

The grade of your shear pin is the problem. As the manual calls for a 5/16 and your pin is drilled for 1/4 stay with that size. Put in a better grade of bolt, a bolt with no markings on the head is a grade ( 2 ) , a triangle or three marks is a grade ( 5 ) , five marks is a grade ( 8 ). Select a long shank bolt so the entire soild unthreaded part is in the yoke. Shim with washers to get the perfect fit. Just remember as you go up in grade the bolts are stronger so move up with caution.
Thats what I did with mine, and on my bench sits a small container of ( Snow blower shear pins ).
Craig Clayton

Thanks Craig. I plan to run it a while with the grade 5 and if I go through bolts for no reason then I will move up a grade. When i broke this first pin I had picked up a rock the size of a cantalope.

 

[Wayne_H]

Have you thought of calling the dealer/manufacturer?

Wayne

 

[TGReaper]

With regard to your shear bolt question,perhaps I can help.

My blower is a 60 in Buhler/Allied but the system is the same.

There are three shear pins, the 1/4 inch one drives the auger and is usually the one that breaks. This just a standard 1/4 in grade 5 bolt and should be replaced with the same thing.

The two 5/16 grade 8 shear bolts are for the shear plates on the pto shaft.
These drive the whole unit but will generally only break when you jam the blower second stage. With out these two shear bolts the the fan,pto and related pieces would have no protection.

Hope this makes sense.

Dan

 

[jake98]

I would think you'd want to stick with soft shear bolts. Rather replace them fifty times than replace the gears.

 

[doxford jim]

As Dan says, there are two sizes of shear bolts. The 1/4" dia shear pin is for the auger drive and the 5/16" dia shear pin is for the input shaft from the PTO.

The 1/4" one is the one that seems to break most frequently - usually stones or bits of wood, frozen dog poo, rocks etc - that sort of thing. The shear pins should be kept tight to prevent the holes being worn oval from slack pins.

I have a 1989 Allied-Farm King 73" blower and it works well. I bought it used last January for a reasonable price and it works great. I have managed to throw the snow probably 30ft or so - and that is with a 3 blade impeller and a tip clearance (well worn) of about 5/8". I am looking at modifying the impeller once I can pull it off the shaft next summer. With good PTO revs, it still throws snow a good distance and I have yet to replace a broken shear pin. The Jinma TPH snow blower I have is frequently breaking shear pins and is no where near as robust or as good as the Allied Farm King one.

I am sure you will be very happy with your new 74" blower - wish I could afford a new one.

Jim

 

[DemcoEd]

I would think you'd want to stick with soft shear bolts. Rather replace them fifty times than replace the gears.

You are partially correct. Grade 8 bolts shear clean whereas a grade 5 will tend to "smear" when they shear. If that happens too often the hole they are in become worn and it will be difficult to hold the shear bolt at that time. If the manual calls for grade 5 or grade 8, USE THEM as instructed in the manual.

 

[pitt_md]

With regard to your shear bolt question,perhaps I can help.

My blower is a 60 in Buhler/Allied but the system is the same.

There are three shear pins, the 1/4 inch one drives the auger and is usually the one that breaks. This just a standard 1/4 in grade 5 bolt and should be replaced with the same thing.

The two 5/16 grade 8 shear bolts are for the shear plates on the pto shaft.
These drive the whole unit but will generally only break when you jam the blower second stage. With out these two shear bolts the the fan,pto and related pieces would have no protection.

Hope this makes sense.

Dan

Dan thanks for the update. That makes sense of what the manual was saying at least.

I am so thankful that I have that unit on the back of my Kubota right now. We are in the middle of one of worst blizzards I have seen in my 15 years living in MN. Over a foot of snow and still coming. It's blowing and drifting so bad I can't see the road in front of my house. It is not supposed to stop until tomorrow. Right now there is a 4' drift in front of the tractor bay in the barn.

Jake,
I don't know what was in there before it broke. I wish the manual called out the grade for the 1/4" bolt or even refered to it as a shear bolt. As I said before I am going with a grade 5.