Where can i buy grade 8 shear bolts

[Brad2023]

Where can I buy a grade 8 shear bolt
1/2 in x 4 in
I use to buy grade 5 but they break to much on bush hog
grade 8 seems to be perfect its strong enough to go through thick stuff if you have to but will break before it messes up gear box but i cant find anywhere that sells them?

 

[old]

Where can I buy a grade 8 shear bolt
1/2 in x 4 in
I use to buy grade 5 but they break to much on bush hog
grade 8 seems to be perfect its strong enough to go through thick stuff if you have to but will break before it messes up gear box but i cant find anywhere that sells them?

Most any hardware store has them as well as farm and home stores

 

[Tim PloughNman Daley RIP]

Where can I buy a grade 8 shear bolt
1/2 in x 4 in
I use to buy grade 5 but they break to much on bush hog
grade 8 seems to be perfect its strong enough to go through thick stuff if you have to but will break before it messes up gear box but i cant find anywhere that sells them?

Here ya go - plenty of options...

McMaster-Carr

McMaster-Carr is the complete source for your plant with over 595,000 products. 98% of products ordered ship from stock and deliver same or next day.

www.mcmaster.com

Also stock 1/2-13 in Grade 8

 

[john in la]

Grade 8 for a shear bolt ?????
You must be looking to do some gear box repairs.
Most manuals will tell you to use grade 2 for safety reasons.
But in secret the techs will tell you to upgrade to grade 5 because grade 2 bends rather than shears making it hard to get the broken piece out.
If you are looking to upgrade to a 8 you need to either clear the obstacle course so you quit running over junk or I more likely suspect you are using the wrong bolts.
Case in point....
The threaded section of a grade 8 bolt has less shear strength than the shank of a grade 5 bolt.
If you are using normal bolts the threaded area is usually in the shear point.
You need full shank bolts with just a small section of threads.
Yes it is a special bolt and hard to find other than getting OEM parts.
Another option is to buy fully threaded bolts.
In this instance you might get away with using grade 8.
A lot of OEM shear pins; wrongly called shear bolts are special made alloy to break at a specified shear point.
You can usually spot them as proper shear pins because of the groves cut in them.

https://www.ariens.com/getattachment/db5c659d-7611-415b-af68-695ab2f74356/two_shear_pins.jpg

 

[Tim PloughNman Daley RIP]

Grade 8 for a shear bolt ?????
You must be looking to do some gear box repairs.
Most manuals will tell you to use grade 2 for safety reasons.
But in secret the techs will tell you to upgrade to grade 5 because grade 2 bends rather than shears making it hard to get the broken piece out.
If you are looking to upgrade to a 8 you need to either clear the obstacle course so you quit running over junk or I more likely suspect you are using the wrong bolts.
Case in point....
The threaded section of a grade 8 bolt has less shear strength than the shank of a grade 5 bolt.
If you are using normal bolts the threaded area is usually in the shear point.
You need full shank bolts with just a small section of threads.
Yes it is a special bolt and hard to find other than getting OEM parts.
Another option is to buy fully threaded bolts.
In this instance you might get away with using grade 8.
A lot of OEM shear pins; wrongly called shear bolts are special made alloy to break at a specified shear point.
You can usually spot them as proper shear pins because of the groves cut in them.

https://www.ariens.com/getattachment/db5c659d-7611-415b-af68-695ab2f74356/two_shear_pins.jpg

yep but figured he knew this

 

[DoubleO7]

Condition of the holes that the bolt is going thru will also play a factor in how long the bolt will last.
No matter which grade you are using.

 

[Brown David]

yep but figured he knew this

I've made that mistake a few times.

Now I never assume anyone knows anything until they prove that they do.

 

[john in la]

Condition of the holes that the bolt is going thru will also play a factor in how long the bolt will last.
No matter which grade you are using.

007
That is something I forgot to mention.

Often OEM shear pins are special size bolts. Say 17/32 or 9/16. Now using a 1/2 inch bolt is loose in the hole. All it takes is for the engine to cough or for you to let out the clutch a little to fast. This causes the pto shaft to get a running start at the shear pin. Brush cutters are especially bad about this because of their hard to get moving but hard to stop once moving properties.

 

[zuhnc]

Never sheared a bolt on the Bush Hog (tm); it is all splines, no shear points. Hitting something or heavy grass just causes the blades to fold back or the engine to quit! (8N) But, the auger does shear its fair share of Grade 5 bolts. Drilling in our rocky ground causes this. I don't know what the shear strength of a grade 8 bolt is, but in tension, it is quite robust. zuhnc

 

[john in la]

Never sheared a bolt on the Bush Hog (tm); it is all splines, no shear points. Hitting something or heavy grass just causes the blades to fold back or the engine to quit! (8N) But, the auger does shear its fair share of Grade 5 bolts. Drilling in our rocky ground causes this. I don't know what the shear strength of a grade 8 bolt is, but in tension, it is quite robust. zuhnc

The splined bush hog gear box is made to be used with a slip clutch.

 

[DoubleO7]

Never sheared a bolt on the Bush Hog (tm); it is all splines, no shear points. Hitting something or heavy grass just causes the blades to fold back or the engine to quit! (8N) But, the auger does shear its fair share of Grade 5 bolts. Drilling in our rocky ground causes this. I don't know what the shear strength of a grade 8 bolt is, but in tension, it is quite robust. zuhnc

I hope you forgot to say you have a pto overunning clutch on the tractor output shaft.

 

[Jim.ME]

Is it a Bush Hog? That is a brand. What model is it? Does it have a "stump jumper"?

If it has sheared many pins, I am going to guess there is wear in the shaft and yoke shear bolt holes, the yoke has some internal wear where it runs on the shaft, and the shaft has some external wear where the yoke runs on it; all of which combine to make it progressively harder to hold shear pins.

Consider adding a slip clutch and using full shank grade 8 or other high strength bolts to hold it to the gear box shaft and the PTO shaft to the slip clutch input. Adjust the clutch to provide driveline protection and not rely on the shear bolts. You may need to adjust the length of your PTO shaft if you do this.

 

[Tim PloughNman Daley RIP]

I hope you forgot to say you have a pto overunning clutch on the tractor output shaft.

yep -an ORC required for brush hogging and mowing for sure. Got other problems if he's snapping shear bolts.

TPD

 

[Fixingfarmer]

Depends on the operation there are cases where grade 8 bolts are used on oem applications it’s up to the designer of the machine. I can specifically think of a 13 inch auger at home that has a grade 8 sheer bolt. It has broken twice in the 10 years I had to go get some new ones the last time they had rusted in the package so bad. If you go in asking for a grade 8 sheer bolt the person behind the counter will give you the same lecture as given here. Just go ask for a grade 8 bolt...

 

[J.Wondergem]

Fastenal has a big variety of them.

 

[ScottNC]

14mm?

 

[Fixingfarmer]

Metric would be a 10.9 grade

 

[ScottNC]

Thanks, I'm aware of the mm bolts grades but I'm not fluent enough to make a recommendation on a grade five comparable.

For grins - it's raining here so stuck in the house - I just looked up an online a PSI to MPa converter. 85,000psi (high end of G5) is close to an 8.8. Two sources used linked below.

Bolt Grades Decoded: Essential Chart for Builders!

US Bolt Grades Chart with Strength Chart The most common SAE bolt grades are Grade 2, Grade 5, and Grade 8. Metric Bolt Grades Chart with Strength Chart

www.cnccookbook.com

psi to mpa at DuckDuckGo

DuckDuckGo. Privacy, Simplified.

duckduckgo.com

 

[Fixingfarmer]

Yes 8.8s are approx 5 10.9 are approx 8
Caterpillar used 12.9 in a lot of stuff so if you need something for a mower gearbox you definitely want to destroy wander in there.

 

[Tim PloughNman Daley RIP]

Where can I buy a grade 8 shear bolt
1/2 in x 4 in
I use to buy grade 5 but they break to much on bush hog
grade 8 seems to be perfect its strong enough to go through thick stuff if you have to but will break before it messes up gear box but i cant find anywhere that sells them?

Shear Bolts are supposed to break when an obstruction is hit. Grade 2 or Grade 5 is typical. That is so you don't do major damage to your hyd system and parts. Advise to always survey the area you are going to brush hog for any hidden obstructions - old cars, fridges, stoves, dead bodies, Jimmy Hoffa. Invest in an ORC for any mowing job and use STABILIZER BARS.

If you are busting bolts you have other issues going on to address. Advise to keep using the Grade 2 or 5 Bolts and determine the root cause of your problem.

Tim Daley (MI)