Snowblower Snowblower sheer bolts.

[Woodland]

I have a 70" blower on the back of my tractor. The blower has two sheer bolts, one on the auger assembly, and one on the pto drive shaft on the tractor side. What I'm wondering is, are the two sheer bolts redundant, or do they each break or sheer under different circumstances?

Since using the blower for the first time I have sheered the bolt on the pto drive shaft twice. It is a serious pain in the &%$ to replace. I have to remove the tractor pto guard to get at it to tighten the nut and have since left the guard off, not something I want to do. If I replace this bold with a somewhat stronger bolt (IM does not give grade but I believe my dealer said both bolts are Grade 2), will this cause the other bolt to break first, or am I asking for trouble by even thinking about this?

 

[PILOON]

We always use grade 5 bolts as sheer pins.
The few times I used lesser grades I found that they would tear, rather than sheer cleanly.
The softer bolt, while failing more often and tearing will also be much harder to drive out as the torn lip is kinda bent over rather than sheered (cut).

 

[GaryF]

The Woods unit I have also takes a grade 5 bolt.

 

[BXRICK]

The answer to your original question I think is that they are not redundant.
My snowblower (a Meteor), has the same setup.
The PTO pin protects everything, obviously.
The auger pin of course protects the auger only.
However, which pin breaks seems "random". I'm sure it's not actually random, but depends on what jams and how, I guess.

My guess is that the fan/gearbox can take a much larger load before needing to be protected as compared ot the auger system. While the bolts may the same (or not), the load they can take before shearing would depend on where they are (for instance, how far out on the rotating shaft).

I can't believe that snowblowers would have the two pins if it weren't necessary. Though stranger things are true.

 

[RickB]

I have a 70" blower on the back of my tractor. The blower has two sheer bolts, one on the auger assembly, and one on the pto drive shaft on the tractor side. What I'm wondering is, are the two sheer bolts redundant, or do they each break or sheer under different circumstances?

Since using the blower for the first time I have sheered the bolt on the pto drive shaft twice. It is a serious pain in the &%$ to replace. I have to remove the tractor pto guard to get at it to tighten the nut and have since left the guard off, not something I want to do. If I replace this bold with a somewhat stronger bolt (IM does not give grade but I believe my dealer said both bolts are Grade 2), will this cause the other bolt to break first, or am I asking for trouble by even thinking about this?

You may get a better answer if you had mentioned the brand and perhaps model of blower. Shearbolt grade varies by application, your dealer may be blowing smoke for all I know by recommending grade 2. But I won't tell you to use a harder bolt unless I know it is appropriate.

 

[Piperflyer]

I use grade 8 bolts on my meteor blower. I was always shearing bolts for no reason with a lower grade. The area I clean out does not have anything foreign to me when I make my pass to clean out, so I know nothing should get in the augers.

 

[tessiers]

They are not redundant.

The one on the auger does not protect the impeller. If I were going to use a hardened bolt I would put it in the auger assembly. I have replaced the PTO shaft in a Tractor and if you think replacing shear pins is a pain try splitting your tractor. I too use grade 5 bolts. The thing I find interesting is that my bush hog uses 1/2" bolts, my finish mower uses 3/8" bolts and my post hole digger uses 5/16 bolts. I guess that has to do with the implement, not the tractor.

 

[Woodland]

The blower is a 70" Pronovost Lynx. The blower came with a M6x40mm bolt in the pto shaft and a 1/4"x1" Grade 2 bolts in the auger assy. These description are directly from the parts list. The 1/4"x1" is a "stadard" bolt and nut with lock washer that you would find at any hardware store, while the 40mm bolt is painted black and comes with a nylon lock nut. I do not see anywhere in the literature where is says this is a grade 2 bolt. According to the dealer when I purchased the blower, I can, if needed, replace the bolts with grade 5, but he "wouldn't suggest going with anything stronger". He also pointed out that I can get the auger bolt at any hardware store, but didn't think I would find the other one except through parts. In light of this, I am reluctant to replace the pto bolt with a generic grade 5 (or grade 2 for that matter) bolt.

 

[RickB]

Your dealer does not understand metric hardware. Metric hardware does not come in grade 2, 5, or 8. The heads are stamped as 4, 7, 8.8, 10.9 or 12.something. Most Pronovost blower PTO shaft shearbolts are 10mm diameter 8.8 hardness which is your standard hardness for many, many metric hardware applications. The majority of metric bolts stocked at our dealership are 8.8 hardness. They should be commonly available by dimension and grade almost anywhere metric hardware is sold. Be sure to buy a length that allows the bolt to shear through the shank, not through the threads (40mm). 10MM locknuts should be a stock item from the same source. It is equally important NOT to use USS or SAE bolts in this location as the diameter will not exactly match which will cause premature failure as well.

 

[Woodland]

Thank you for the metric lessons. I was not aware of the differences in hardness ratings. Also, not to sound too ignorant but...you mention that the bold should be long enough that the bolt shear through the shaft as opposed to the threads, however, the bolts that came with the blower are threaded all the way up to the head. Can you think of a reason why a manufacturer (especially one from Canada where metric reigns supreme) would use metric for one bolt and SAE for another? And another question (sorry about the whole "teach me metrics" thing), I am under the impression that the M6 is refering to the pitch of the threads?

 

[RickB]

Thank you for the metric lessons. I was not aware of the differences in hardness ratings. Also, not to sound too ignorant but...you mention that the bold should be long enough that the bolt shear through the shaft as opposed to the threads, however, the bolts that came with the blower are threaded all the way up to the head. Can you think of a reason why a manufacturer (especially one from Canada where metric reigns supreme) would use metric for one bolt and SAE for another? And another question (sorry about the whole "teach me metrics" thing), I am under the impression that the M6 is refering to the pitch of the threads?

The PTO shafting is sourced by the blower manufacturer from a third party that specializes in drivelines. Few, if any implement manufacturers make their own PTO shaft assemblies, including Deere, CNH or AGCO, let alone short line manufacturers. The best value in PTO shaft assemblies currently is of a metric design, hence metric standards and dimensions on all things related to your PTO shaft except perhaps the attaching yoke bore diameters which are dependent on matching the tractor and implement. M6 (or M10) refers to the bolt diameter. Thread pitch is expressed as a decimal eg M10-1.25x40MM would be a 10mm diameter bolt with a 1.25 thread pitch 40MM long. 40MM bolts can be obtained either fully threaded or partially threaded. Of all the criteria you need to look for, settling for a full thread bolt is an acceptable choice. I would prefer shearing through a full shank just to get that little 'extra'. I'm a little surprised the original was full thread, but certainly won't dispute the fact.

I apologise for constantly referring to your PTO shearbolt as a 10MM. I re-read you post and see it is 6MM. The rest of my posting is accurate, and I would be even more diligent about finding M6x40 bolts with a full diameter shank at the shear point. 6MM seems small for the PTO shearbolt. My Puma 74 has an M10 bolt in its PTO.

 

[WilliamBos]

Our Buhler Farm-King calls for Grade 8 shear bolts.

 

[atgreene]

Get a slip-on clutch for your pto shaft and adjust accordingly so it will slip before the pins shear. Make sure you shorten the shaft as necessary to avoid binding the drive shaft by making it too short.

I did it to my blower to avoid replacing shear bolts.

Here's a link: http://www.tractorsupply.com/webapp...10551_10001_28194_-1______?rFlag=true&cFlag=1

 

[Woodland]

That is a very interesting option. I may look into that.

 

[atgreene]

Just make sure you properly adjust the clutch to slip when needed.

 

[SPYDERLK]

Thank you for the metric lessons. I was not aware of the differences in hardness ratings. Also, not to sound too ignorant but...you mention that the bold should be long enough that the bolt shear through the shaft as opposed to the threads, [[[however, the bolts that came with the blower are threaded all the way up to the head.]]] Can you think of a reason why a manufacturer (especially one from Canada where metric reigns supreme) would use metric for one bolt and SAE for another? And another question (sorry about the whole "teach me metrics" thing), I am under the impression that the M6 is refering to the pitch of the threads?

Apparently th operation does not call for the extra shear strength of a full shank bolt. The threads give the function of a notch at each shear point as you will often see done on full shank bolts modified for use as shear. Full thread provides a cheap alternative.
larry

 

[Bedlam]

Just wanted to throw this link as well what a difference in price from the TSC clutch. They look the same but maybe there is a difference.
SLIP CLUTCH W/1-3/8X6 MALE X 1-3/8X6 - Agri Supply

or

Tractor Supply Company - PTO Slip Clutch, 1 3/8 in x 1 3/8 in

 

[GreenMtns]

The PTO shafting is sourced by the blower manufacturer from a third party that specializes in drivelines. Few, if any implement manufacturers make their own PTO shaft assemblies, including Deere, CNH or AGCO, let alone short line manufacturers. The best value in PTO shaft assemblies currently is of a metric design, hence metric standards and dimensions on all things related to your PTO shaft except perhaps the attaching yoke bore diameters which are dependent on matching the tractor and implement. M6 (or M10) refers to the bolt diameter. Thread pitch is expressed as a decimal eg M10-1.25x40MM would be a 10mm diameter bolt with a 1.25 thread pitch 40MM long. 40MM bolts can be obtained either fully threaded or partially threaded. Of all the criteria you need to look for, settling for a full thread bolt is an acceptable choice. I would prefer shearing through a full shank just to get that little 'extra'. I'm a little surprised the original was full thread, but certainly won't dispute the fact.

I apologise for constantly referring to your PTO shearbolt as a 10MM. I re-read you post and see it is 6MM. The rest of my posting is accurate, and I would be even more diligent about finding M6x40 bolts with a full diameter shank at the shear point. 6MM seems small for the PTO shearbolt. My Puma 74 has an M10 bolt in its PTO.

Well since I just had my first auger shearbolt go and had to replace it AND I came across this thread that got me looking at my Puma 64.

RickB, I have gone through the parts list for this blower and there is not a single Metric bolt in the blower. Odd, since it's made in Canada.

The manual states on page 10 section 11--Always use Grade 5 shear bolts. BUT

On page 15 of the parts list it reads Ref: 25 Part# Std. Shear Bolt 1/4" NC x1" lg grade 2 + nylon locknut.

They also don't list any other bolts as a shearbolt but do show a Ref 8 Part # 300-32370 Bolt 1/4 NC x2 1/2 lg + nylon locknut at the PTO shaft end on the blower. I assume (and we all know what assuming does ) that this is the PTO shearbolt.

They kind of contradict themselves in a few places but I am going to use a grade 5 at all points since the instructions clearly state that grade for all shearbolts.

 

[RickB]

Well since I just had my first auger shearbolt go and had to replace it AND I came across this thread that got me looking at my Puma 64.

RickB, I have gone through the parts list for this blower and there is not a single Metric bolt in the blower. Odd, since it's made in Canada.

The manual states on page 10 section 11--Always use Grade 5 shear bolts. BUT

On page 15 of the parts list it reads Ref: 25 Part# Std. Shear Bolt 1/4" NC x1" lg grade 2 + nylon locknut.

They also don't list any other bolts as a shearbolt but do show a Ref 8 Part # 300-32370 Bolt 1/4 NC x2 1/2 lg + nylon locknut at the PTO shaft end on the blower. I assume (and we all know what assuming does ) that this is the PTO shearbolt.

They kind of contradict themselves in a few places but I am going to use a grade 5 at all points since the instructions clearly state that grade for all shearbolts.

My response was directed to the owner of a Pronovost Lynx which has a metric shearbolt in the PTO. He was being given bad advise by someone who does not understand metric hardware, specifically that the 6mm PTO shearbolt was of grade 2 hardness. The point of my post was to inform the OP on how to describe and source metric hardware; not to make blanket claims about everybody's snowblower shearbolts.

I'm baffled as to why you are comparing your snowblower to mine even though they are different sizes and models and based on the information we have both given, apparently have different series driveshafts with different sized shearbolts. The best advise I can give you is to follow the info published in your operator's manual.

 

[GreenMtns]

My response was directed to the owner of a Pronovost Lynx which has a metric shearbolt in the PTO. He was being given bad advise by someone who does not understand metric hardware, specifically that the 6mm PTO shearbolt was of grade 2 hardness. The point of my post was to inform the OP on how to describe and source metric hardware; not to make blanket claims about everybody's snowblower shearbolts.

I'm baffled as to why you are comparing your snowblower to mine even though they are different sizes and models and based on the information we have both given, apparently have different series driveshafts with different sized shearbolts. The best advise I can give you is to follow the info published in your operator's manual.

I fully understood your post and was not calling you down on it. I am just a little confused by my manual which is telling me one thing on one page and a completely different thing on another. It might be because my blower is 6 years old and maybe a design from "the past".