Grade 5 Shear Bolts

[dirtydeed]

I'm having some difficulty finding 5/16" x 2.5" grade 5 shear bolts (these are for PTO shaft on flail mower)...looked at TSC, Amazon and McMaster Carr without any luck. Anyone else have a supplier?

I see some on amazon that mention that they are used for Kubota snow blowers...but I think that they are Grade 2 for the auger drives...

 

[Old Machinist]

Lowes lists a fine thread grade 5 in that length.

https://www.lowes.com/pd/Hillman-5-16-in-x-2-1-2-in-Zinc-Plated-Fine-Thread-Hex-Bolt-2-Count/3012776

 

[dirtydeed]

wasn't sure if I needed an actual shear bolt or if any grade 5 bolt would do.

 

[Old Machinist]

If it calls for grade 5 and you find a grade 5 bolt that fits it should be okay. It doesn't have to be called a shear bolt. The hardness and fit is what matters.

 

[RCW]

If it calls for grade 5 and you find a grade 5 bolt that fits it should be okay. It doesn't have to be called a shear bolt. The hardness and fit is what matters.

I would never disagree with a member whose moniker is "Old Machinist."

I'd go with a straight Grade 5 as he suggests.

Just my snowblower model BX2750D, but they're grooved OEM shear bolts for mine.

Look like a grade 8 (right) for the impellor, and two grade 2 or 5 for the auger.

Not sure that's what you want for your application.

 

[Magicman]

You are risking a u-joint using a grade 5. My cutter uses a grade 2.

 

[mcfarmall]

You are risking a u-joint using a grade 5. My cutter uses a grade 2.

Minimal risk if the owners manual says Grade 5.

 

[NCL4701]

I'm having some difficulty finding 5/16" x 2.5" grade 5 shear bolts (these are for PTO shaft on flail mower)...looked at TSC, Amazon and McMaster Carr without any luck. Anyone else have a supplier?

I see some on amazon that mention that they are used for Kubota snow blowers...but I think that they are Grade 2 for the auger drives...

5/16 x 2.5” Grade 5 shear bolts (with the groove if that’s what you’re wanting):

Amazon.com: XTPTFABS (10Pcs) 70060-01337 Shear Bolts 5/16" x 2-1/2" Compatible with Snowblower B2781 : Patio, Lawn & Garden

Buy XTPTFABS (10Pcs) 70060-01337 Shear Bolts 5/16" x 2-1/2" Compatible with Snowblower B2781: Snow Blower Replacement Parts - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

Scroll down to “specifications” section for grade.

 

[Old Machinist]

I would never disagree with a member whose moniker is "Old Machinist."

I'd go with a straight Grade 5 as he suggests.

Just my snowblower model BX2750D, but they're grooved OEM shear bolts for mine.

Look like a grade 8 (right) for the impellor, and two grade 2 or 5 for the auger.

View attachment 158824

Not sure that's what you want for your application.

I can be as wrong as the next guy. I have never seen these grooved "shear bolts".

 

[Old Machinist]

I'm having some difficulty finding 5/16" x 2.5" grade 5 shear bolts (these are for PTO shaft on flail mower)...looked at TSC, Amazon and McMaster Carr without any luck. Anyone else have a supplier?

I see some on amazon that mention that they are used for Kubota snow blowers...but I think that they are Grade 2 for the auger drives...

How are these described in your flail mower manual? What brand and model is it?

The snow blower "shear bolts" linked above are listed as stainless steel.

 

[Magicman]

Minimal risk if the owners manual says Grade 5.

Yes, always use what the owner's manual specifies. As I stated, mine uses a grade 2.

 

[Spam Bot]

This is what happens when the wrong bolt is used in place of the correct bolt. It can cause premature failure of the gears that the shear bolt is intended to protect. This results in an expensive repair and significant downtime. Have you considered a slip clutch in place of the shear pin arrangement?

 

[GreensvilleJay]

That groove is the 'weak' point of the 'shear bolt' and usually it'll be aligned with where the 'shaft' and 'coulping' meet. Suppose it makes it easier to replace, as one or both busted pieces will 'magically disappear'. All 'shear bolts' are regular bolts WITH the groove. You can make your own, just chuck bolt in drill and lightly score a groove with hacksaw blade.

 

[whatsupdoc]

Buy the correct shear bolt as designed by the manufacture.

 

[dirtydeed]

The bolt didnt break it was just a bit loose so I snugged it up. I was just thinking that it'd be good to have a spare. I took it out for a look and it just appears to be a standard hex bolt. There aren't any precut grooves in it.

all that I can find for info is from BETSTCO website-

"The PTO shaft is included with purchase of machine. These machines come with an 80cm (31.5 inch) PTO shaft fully collapsed. Shear bolt size depends on mower size. EFG105 up to EFG135 comes with a Series 04 PTO shaft, shear bolt is 5/16 bolt, 2.5 inches long, Grade 5."

Service in the "PTO manual" simply states to replace the bolt with one of same length, diameter and grade. It doesn't really say anything about it being an actual "shear" bolt.

 

[BAP]

A lot of shear bolts are NOT grooved. Each manufacturer determines what is best for their application.

 

[TheOldHokie]

Shear strebgth is proportionsl to cross sectional area in shear. All the groove does is reduce the cross sectional area thats in shear.

The most common engineering formulas for calculating shear strength of steel fasteners are .5 or .55 x yield strength. So its easy to calculate the shear strength of any grade bolt with or without the groove. You can make a grade 8 bolt shear at the same load as a grade 5 by cutting an annular groove of the appropriate diameter at the shear plane. That groove MUST be coincident with the shear pIane or it has no effect.

Dan

 

[RCW]

I have no idea of the application(s), but I would often see farmers I know at TSC buying grade 2 or 5 bolts by the pound to be used as shear bolts.

Was usually around haying season, if I recall correctly.

 

[TheOldHokie]

I have no idea of the application(s), but I would often see farmers I know at TSC buying grade 2 or 5 bolts by the pound to be used as shear bolts.

Was usually around haying season, if I recall correctly.

I keep both front pockets full of Grade 5 bolts and nuts when tilling the garden with my Troy Bilt

Dan

 

[RCW]

The grooved ones I pictured earlier for my snowblower are $8-10 for a set of 3.

I've chosen to use OEM because of the grooves and keep several sets on-hand. If I break one, I'm sure to break two or three....better than the gearbox on the blower, etc. (I usually only break one or two per season).

Gets back to @TheOldHokie 's point on where and how grooves are, if required at all.

Could buy several straight 5/16x2.5" grade 5 for a $1 or 2.