Shear pin question

[Smoke244]

Guys, first year with the Kubota with a front blower, tractor is a BX2200 with a BX2750 front blower. Show is went and heavy and the second stage shear pin did its job and sheared. The bad news is the only pins I have on hand are for the first stage shaft. The dealer is closed today and tomorrow and the snow is still coming. Thoughts on using a standard bolt for this.

 

[Bmyers]

Well if you can see the bolt head or maybe the manual will tell you what grade of bolt (2 or 5 is my guess), you can go to the local hardware/tractor store and pick some up. The last bolts I picked up for dad was from tractor supply for his rotary mower.

(FYI-if you go into many places now days and ask for a shear bolt, a lot of the sales people will have no idea what you are talking about; ask for the grade of bolt you need and they will lead you right to it.)

PS-if you don't know the grade, always go lighter so you don't tear anything up.

 

[Smoke244]

Well if you can see the bolt head or maybe the manual will tell you what grade of bolt (2 or 5 is my guess), you can go to the local hardware/tractor store and pick some up. The last bolts I picked up for dad was from tractor supply for his rotary mower.

(FYI-if you go into many places now days and ask for a shear bolt, a lot of the sales people will have no idea what you are talking about; ask for the grade of bolt you need and they will lead you right to it.)

PS-if you don't know the grade, always go lighter so you don't tear anything up.

Bolt head is gone so I will go with soft grade to hopefully get this weekend behind me and grad a few at the dealer on Monday. That was my original plan but wanted to put it out there to the experts. Love the forum!

Anyone else have input don’t hold back.
Have a safe holiday season everyone.

 

[Bmyers]

Did a search on Messicks.com, found the part number for the shear bolt ( 70060-01075 ).

Searched for the part, came up with the Amason link below, which shows it is a grade 5. Yet, it is Amazon and parts have been wrong on there before.

Amazon.com: Kubota BX and Others Shear Bolts Snowblower Tractor pins Auger and Fan 70060-01338 70060-01075: Garden & Outdoor

Current part number 70060-01338,70060-01075
High quality Grade 5 bolts just like the original manufacturer. Grooved to the same specs. You will receive 10 auger shear bolts, 10 fan shear bolts and the nylon lock nuts for both. Part numbers are for reference to original Kubota parts. These are aftermarket bolts cut to the same specifications as factory bolts where applicable. Bolts may have cutting fluid residue left from manufacturing process. Will not impact functionality.


Auger bolt part # Replaces 70001-00538, 70050-94176 fits models listed below for auger bolts B2550 (50" ECONO . SNOWBLOWER) B2550C(S . No . 2010000 AND UP) (50" ECONO . SNOWBLOWER) BX2750 (50" FRONT SNOWBLOWER) BX2750(S . No . ;>=9900101) (50" FRONT SNOWBLOWER) BX2750A(S . No . 2303678 AND UP) BX2750A(S . No . 2303678 AND UP) (50" SNOWBLOWER) BX2750B (50" FRONT SNOWBLOWER) BX2750B(S . No . 2500000 AND UP) (50" FRONT SNOWBLOWER) BX2750C(S . No . 2508091 AND UP) (50" FRONT SNOWBLOWER) BX2750D(S . NO . 2707375 AND UP) (50" FRONT MOUNT SNOWBLOWER) BX2816 50" SNOWBLOWER BX5450 BX5455HD G2003 (46" BLADE ATTACHMENT . .) G2538A (38" 2-STAGE SNOWBLOWER) G2538B (38" 2-STAGE SNOWBLOWER) G2546A (46" 2-STAGE SNOWBLOWER) G2726(S . No . 2406356 AND UP) (52" FRONT SNOWBLOWER) GF5225S . No . 2020379 AND UP GR2707(S . NO . 2503711 AND UP) (46" SNOWBLOWER / GR10 SERIES)


Fan bolt part # replaces Replaces and should fit 70001-00539 B2550 (50" ECONO . SNOWBLOWER)B2550C(S . No . 2010000 AND UP) (50" ECONO . SNOWBLOWER)BX2750 (50" FRONT SNOWBLOWER)BX2750(S . No . ;>=9900101) (50" FRONT SNOWBLOWER)BX2750A(S . No . 2303678 AND UP)BX2750A(S . No . 2303678 AND UP) (50" SNOWBLOWER)BX2816 50" SNOWBLOWERBX5450G2003 (46" BLADE ATTACHMENT . .)G2538A (38" 2-STAGE SNOWBLOWER)G2538B (38" 2-STAGE SNOWBLOWER)G2546A (46" 2-STAGE SNOWBLOWER)GF5225S . No . 2020379 AND UPTG2542 (SNOWBLOWER)TG2746A(S . No . ;>=2006202) (46" TWO STAGE SN

Also Replaces 4263511m91 4263512m91

 

[GreensvilleJay]

I've used regular grade 5 bolts for decades with all kinds of snow, without any problems and I can't be THAT lucky for it to be a problem...
With wet, heavy stuff, take less 'snow 'and go slower, get rid of rid....

 

[Bmyers]

Also, I zoomed in on your picture and right next to your finger is a Grade 5 bolt (3 lines).

 

[Smoke244]

Thanks for all the fantastic information guys. I finished the lot with grade 2 bolts. Took four but got it done. Going to the hardware tomorrow for some grade 5s to do the lot one more time tomorrow. We don’t expect as mush snow tomorrow so it should go well with grade 5s. When the 2s keep popping I figured they were to soft. Better safe thank sorry though.

 

[Wiz]

Thanks for all the fantastic information guys. I finished the lot with grade 2 bolts. Took four but got it done. Going to the hardware tomorrow for some grade 5s to do the lot one more time tomorrow. We don’t expect as mush snow tomorrow so it should go well with grade 5s. When the 2s keep popping I figured they were to soft. Better safe thank sorry though.

Better too soft and popping than the reverse. BTW I bought the big pack from that vendor on Amazon. I haven't opened the package but will tomorrow as I sheered an auger pin last week

 

[mikester]

I've used grade 2 carriage bolts that have full threads as well as shoulder bolts. Works well with augers, snowblowers, shears off cleanly and easy to remove after.

Shoulder bolts have a bigger cross section and will resist shear better.

I wouldn't go with higher grade bolts. Remember that shear bolts are cheaper than driveline and gearbox parts.

 

[GreensvilleJay]

re: Shoulder bolts have a bigger cross section

I assume you mean compared to real 'shear' bolts..

 

[hope to float]

I've used grade 2 carriage bolts that have full threads as well as shoulder bolts. Works well with augers, snowblowers, shears off cleanly and easy to remove after.

Shoulder bolts have a bigger cross section and will resist shear better.

I wouldn't go with higher grade bolts. Remember that shear bolts are cheaper than driveline and gearbox parts.

Shoulder bolts have an entirely different meaning here. They are the ones left over after reassembling something so you throw them over your shoulder

 

[Russell King]

The statement simply meant that the unthreaded shank of a bolt has a slightly larger shear surface than a threaded section or an undercut section of the same bolt size.

 

[torch]

Grooved to the same specs.

Big red flag. Don't use regular grade 5 bolts in an application that requires a grooved bolt. Stick with the grade 2's as an emergency replacement.

Grooved bolts have a smaller diameter at the shear line. They are used where the shear bolt goes through a shaft and are sized so the two grooves align with the OD of the shaft. A regular Gr. 5 bolt will not only be too strong, it will be too strong on one side -- the threaded end will want to shear before the shoulder end, which can result in an elongated, distorted hole and/or damaged shaft.

Regular bolts are used on a flange between two shafts. As a result, they only have one shear point.

 

[Smoke244]

Today I stopped at the Kabota dealer and picked up the correct shear pins by part number. When the parts counter handed them over it appeared to me that they are straight grade 5 bolts. After installing one I noticed that the shoulder on these bolts is not at the shear point, it’s beyond it. I am all about using factory OEM parts and will be leaving these in however, because I expected the transition from shoulder the tread to be at the shear seam that got me wondering what some of you thought of this versus a threaded full length grade 5 bolt? The treaded full length seems like it would shear sooner placing a good safety margin on the assembly and make a great bandage if you need one on a day the dealer is closed. There is to be a lot of knowledge on here, I’m interested in your thoughts.

 

[torch]

That's fine, and quite common.

 

[MNVikingsGuy]

Lots of interesting info, but at $1.60 apiece for Kubota factory replacements, I am sticking with those - I am not trying my luck with Amazon or ebay purchase to save $0.45 on a part that is mission-critical to a $7,000 blower. YMMV.

 

[GeoHorn]

I suspect the “official Kubota” part is a common Gr5 bolt to which they assign a part-number.

A Gr5 bolt will shear and protect the driveline of the tractor just fine and shouldn’t cause worry, IMO. There’s no need to use a softer bolt ...the drive line is made of much hardier facings than that 3/8” bolt can withstand in shear. Tension would be a different matter, but think of the gear-teeth intermeshing: There is considerably more surface-area than the small cutting/shear-area of the implement, and this is another one of those “measure it with a micrometer, mark it with a grease-pencil, and cut it with a hatchet” situations.

 

[Jonny]

I've used regular grade 5 bolts for decades with all kinds of snow, without any problems and I can't be THAT lucky for it to be a problem...
With wet, heavy stuff, take less 'snow 'and go slower, get rid of rid....

Prior owner used Grade 8 in the impeller. I had the key shear on the the driven sprocket. It made a mess of things. Only Grade 5 with the reliefs cut in them for me.

 

[Blue2Orange]

I've used std hardware bolts of the correct grade when in a pinch on the old NH's Loftness snowblower. Sometimes a PITA to remove after shearing. The driveline one required removing the snowblower uni joint shield which stayed off forever. Using a punch to drive out the remaining chunk. The bolt would shear, but leave enough of a barb that sort of wedged or snagged that chunk. The front uni joint that is adjacent to the pto coupler was always a pita. Not a good design. A slot held the bolt head so you only needed one wrench to snug down the locknut. Shear plane was at the nut end leaving the head and shaft of the bolt stuck inside the assembly. With a similar barb or whatever jamming in the remanent of the bolt. Have to remove the driveline shaft and then drill out that chunk. Did I note. PITA!!!

Real shear bolts. Never remember needing to drill out or punch out a broken shear bolt. Minimal cost of real shear bolts. Picked up an handful assortment for the new LP snowblower at the dealer. Local ACE hardware doesn't stock real shear bolts anymore. Guessing people look at $2 shear vs $1 std bolts and have been going cheap0. No sales, limited space, no need to stock.

Personal opinion. Don't go cheapO when it comes to shear bolts. Tighten to correct torque. Over tightening just stresses the bolt. Simple, effective preventive maintenance.

 

[torch]

The bolt would shear, but leave enough of a barb that sort of wedged or snagged that chunk.

Typical of a softer bolt like Gr. 2. They tend to tear and deform prior to shearing. Particularly problematic when the shear bolt goes through a shaft so there are two shear planes involved. Purpose-made shear bolts for that application usually feature a groove at each shear plane so the rough bits don't reach the bore.

Flanged applications with a single shear plane are less problematic -- simply ensure the thread extends to the shear plane -- Voila, instant groove. But flanged joints are heavier and more expensive to manufacture so they are not often found on light weight or budget priced equipment.

Harder bolts tend not to deform and to snap cleanly. Of course, using a harder bolt than the manufacturer specified may lead to damage since the bolt will also take more force than the correct grade. The manufacturer will also have taken diameter of the bolt and/or groove into account when designing things.

My blower has flanged joints and the manufacturer specs Gr5 standard bolts so that's what I use. But I have had the through-shaft style on other equipment in the past. In a pinch I would chuck up a standard Gr. 2 in the lathe and cut a couple of grooves at the shear planes to mimic OEM. It works until you can get more of the proper ones.