Grade 2 VS Grade 5 Shear Bolts- Kubota Says Either is Good.

[LDowney]

Hey guys. Just wanted some feedback from you more experienced guys. The manual that came with my King Cutter bush hog and my Auger both state to only use Grade 2 shear bolts. The rotary cutter uses the 1/2" X 3" bolt and my post hole digger uses 5/16th" X 2 1/2" bolt.

I called my local Kubota dealer today and told then when I went to Lowes yesterday to pick up a few extra shear bolts, all Lowes carries is Grade 5 and Grade 8. The guy at my Kubota dealer told me to just use the Grade 5 bolts. He told me that's what they use in all their implements and seems to work just fine. What concerns me is both my manuals state my warranty will be voided if I use a shear bolt higher than Grade 2.

What experience do you guys have with the Grade 5 bolts from Lowes or Home Depot? I'm just worried they won't shear at the set point like a Grade 2 bolt will. I don't want to damage my equipment but when Kubota is telling me to just use Grade 5, it leaves me scratching my head.

Your thoughts?

 

[D2Cat]

Why not use grade 2? Then you have no quandaries with warranty. If you end up shearing a bolt too frequently use a grade 5, or quit working in the soil conditions that cause the grief!

The grade of a bolt should have no bearing on where you purchased the bolt.

 

[bcbull378]

Go to your local mom and pop hardware and buy a handful of grade 2 bolts and be done with it. Don't use anything but grade 2 or you'll regret ever it if you hit a rock with grade 5 or 8 you'll twist your auger drive line .

 

[CountryBumkin]

I'm surprised that your Kubota Dealer would tell you it is okay to use either a grade 2 or grade 5 bolt. There is a big difference in the shear strength.

I wonder if that Kubota guy would remember (or confirm) telling you a grade 5 was okay if you were to come in with a warranty claim after admitting to using a grade 5.

Manufacturers don't list Shear Strength for their bolts, but the way it is usually determined is to take the Tensile Strength and multiply by .60 (Shear Strength is 60% of Tensile Strength).

So a 3/8-16 Grade 2 both has a Tensile Strength of 5750, therefore the Shear Strength is 3,450.

A 3/8-16 Grade 5 bolt has a Tensile Strength of 9300, so the Shear Strength is 5,580.

That's a 38% difference.

 

[LDowney]

Go to your local mom and pop hardware and buy a handful of grade 2 bolts and be done with it. Don't use anything but grade 2 or you'll regret ever it if you hit a rock with grade 5 or 8 you'll twist your auger drive line .

True. Up until just a few minutes ago, I could not find anyone that sold grade 2 bolts. I checked with my Advance Hardware store. They have grade 2 and grade 3 bolts that will work. I feel a little better using a grade 3 bolt than the grade 5 ones at Lowes.

 

[LDowney]

Here is the bolt top they sent me a picture of. Can anyone confirm it's grade? It reads HFE at the top and 3 lines with a curved line through them.

 

[mendonsy]

That appears to be some sort of manufacturer's mark. Here's a bolt grade identification chart.
http://engineersedge.com/hex_bolt_identification.htm

 

[85Hokie]

I have to agree with CB,

I would rather replace a dozen grade 2 bolts and cuss each time, than throw a grade 5 and replace the drive-train once, can you imagine the words used then!

 

[Grouse Feathers]

Standard everyday bolts are grade 2. Lowes at least the local Lowes here carries grade 2 bolts they just are not labeled as grade 2. If in doubt go to the local hardware (as recommended by others) as most have standard every day bolts labeled as grade 2.

 

[BAP]

Tractor Supply carries a good selection of Grade 2 bolts, as well as Grade 5 and 8.

 

[LDowney]

Tractor Supply carries a good selection of Grade 2 bolts, as well as Grade 5 and 8.

Great suggestion. I have one of those close by.

Thanks.

 

[steveInMaryland]

Fastenal will hand over exactly what you ask for. Check and see if one is in your area. Their prices are also much better.

Not to say you shouldn't use a grade 2 but how the heck would they know you used a grade 5? I stand by better safe than sorry but when the officer says "Do you know how fast you were going?" I'm fairly sure 55 will come out my mouth.

 

[RCW]

Tractor Supply carries a good selection of Grade 2 bolts, as well as Grade 5 and 8.

By the pound - can't beat them for anything like that.

Seems like Grade 2 is $3/pound or so.

My Kubota snowblower shears are over $2 a piece, but factory, so I choose to stay with them. Blower has 3 shears, and 2 types. Much more sensitive/precise application. Only busted a couple in 3 seasons.

 

[dfh1977]

Tractor supply also sells the grade 2 nuts and bolts by the pound. Paid $3 for a big bag. Versus $1 A BOLT by manual from Kubota. Went thru 5 in 1 day tilling ground. Otherwise you could go with savings of the non shear bolt drive shaft that pops out of place with spring if you hit something. Cost of it does not work out once you learn how and can quickly change a shear pin.


Sent from my iPhone using Tapatalk

 

[nickelplated5s]

My Kubota snowblower shears are over $2 a piece, but factory, so I choose to stay with them. Blower has 3 shears, and 2 types. Much more sensitive/precise application. Only busted a couple in 3 seasons.

Why? Grade 2 is grade 2. The bolt ID chart was interesting though. I had no idea there were things like an 8.1. Probably for something Mech. Eng's spec out specfically.

 

[GaltsGulch]

I use grade 5 in my post hole digger. If I used grade 2 I would go through multiple bolts per hole. In my soil the grade 5 bolts will last me at most 3-4 holes and that is with babying the auger so it doesn't get stuck in the ground and cause me to have to unscrew it from the ground manually. My soil is pretty rocky. My tractor doesn't have any problems breaking grade 5's and not even skipping a beat. Doesn't seem to do any damage to the tractor or the auger. I would like to switch my pto auger for a hydro unit on the FEL but that's a different thread. How would they know if you used grade 5 or 2 if the unit breaks and the pins aren't in it when you take it in?
Tractor supply in their tractor section has bags of 5 nuts and bolts grade 5 for sheer bolts.

Good luck.