Shear Bolt vs Regular Bolt

[MikePA]

I stopped at my local TSC to buy some 1/2 x 3" Grade 2 shear bolts for my Brush Bull rotary mower. They didn't have any and the salesman said, "All the guys are using regular bolts of the same size." So, I went over to the fastener section. They had Grade 8, Grade 5 and Steel bolts, according to the labels on the drawers. No Grade 2 bolts. Is it OK to replace a shear bolt with a regular Grade 2 bolt?

 

[RobS]

Mike, stick with the grade 2 even if you have to go elsewhere to find it. The higher grades will be tougher and may not shear when they need to. That could result in damage to your PTO driveline. As I recall, grade 2 will have NO markings on the head. The other grades will have various raised marks forged into the bolt heads. Hope this helps /w3tcompact/icons/smile.gif

 

[Spencer]

This is out of my Bush Hog Rotary Cutter Manual.

 

[MikePA]

Thanks, Spencer and Rob!

Do either of you know if there is a difference between a Grade 2 bolt and a Grade 2 shear bolt?

 

[Anonymous Poster]

<font color=blue>...if there is a difference between a Grade 2 bolt and a Grade 2 shear bolt? ...</font color=blue>

Yep... the word shear.../w3tcompact/icons/smile.gif

Actually some "devoted" shear bolts will have a "groove" cast into the bolt...

 

[MikePA]

The shear bolts on my snow blower have the groove, two of them I think.

So, is it safe to replace a Grade 2 shear bolt with a Grade 2 regular bolt?

 

[jasonf]

On my snowblower there are 2 shear bolts for the auger and 1 for the fan. The shear bolts cost around $6 each, and I am always going thru them. I use the grade 2 bolts (which the original shear bolts were) and use my lathe to make the grooves in them. You could also make the grooves in them by chucking the bolt into a drill and then hold a file to the bolt areas that you want the grooves to be. (A dremel works even better to make the grooves). I make up 20 of them in the beginning of the snow season and they cost a few cents each vs $6. BTW I always add 2 to the number of hash marks on a bolt to get the grade. 3 hash marks on the bolt head is a grade 5, 0 hash marks on the head is a grade 2. I find that if you don't make the groves in the bolts they are harder to drive out of the shaft after they shear,/w3tcompact/icons/sad.gif if you do have the grooves they just pop right out !!/w3tcompact/icons/smile.gif Hope this helps.

 

[Milbrand1951]

Geez, this is an old thread but exactly what I am going through now. My neighbor picked up some bolts for at TSC and they keep breaking. When I bought my rotary cutter the original bolt lasted a long time even with an inexperienced operator, myself. I am going to the JD dealership to find out about the right bolt which is a Grade 2 and ordering it through them.

 

[redtide91356]

Listen to Rob S. That's exactly what happened to me. I used a grade 5, hit a wellhead that nobody knew about and instead of the bolt breaking, the pto shaft got stripped at the yolk where it attaches to the tractor. You have to replace #2's more often but that's what they are supposed to do. John H.

 

[Milbrand1951]

I went through this mess last summer. Rob S is right but JD didn't have the right bolt in stock and sold me a #5 which I am using. Am being extra careful with it.

 

[RickB]

The shear bolts on my snow blower have the groove, two of them I think.

So, is it safe to replace a Grade 2 shear bolt with a Grade 2 regular bolt?

The term shear bolt is terribly misunderstood. They come in all grades, with relief grooves or without. Every machine that uses shearbolts also has a specification and/or part number correct for that application. That spec may be grade 2,5,or 8 with or without relief grooves. There are metric shearbolts in 4, 8.8 & 10.9 hardnesses. Learn your machine's shearbolt requirement and buy the correct bolt wherever you choose.
The majority of shearbolts are common hardware of a particular size and hardness available from a variety of sources.

 

[boggen]

Geez, this is an old thread but exactly what I am going through now. My neighbor picked up some bolts for at TSC and they keep breaking. When I bought my rotary cutter the original bolt lasted a long time even with an inexperienced operator, myself. I am going to the JD dealership to find out about the right bolt which is a Grade 2 and ordering it through them.

many rotatory cutters, have a "slip clutch" on them. located between the PTO shaft that and the Gear box on the rotatory cutter. it most likely looks like a big metal wheel with springs or skid plates on it. it might be easier to figure out the slip clutch vs constantly relying on a sheer bolt.

 

[Gale Hawkins]

many rotatory cutters, have a "slip clutch" on them. located between the PTO shaft that and the Gear box on the rotatory cutter. it most likely looks like a big metal wheel with springs or skid plates on it. it might be easier to figure out the slip clutch vs constantly relying on a sheer bolt.

This old cutter was purchased by the late FIL sometime after buying the tractor in 1977 and it has a slip clutch which I love. I was working in some 3 years of over growth and did not realize it was slipping and had to replace the circles of clutch material. It was under $10 and not a hard job but setting the tension was trial and error since it was my first experience. Now if it goes to slipping cutting trees the size of my wrist I get it out of the load fast and let it recover. It is a 6' cutter and very heavy duty.

 

[MossRoad]

I hope Mike listened to Rob.... it was 12 years ago! :laughing:

Still good advice, though.

 

[MikePA]

I hope Mike listened to Rob.... it was 12 years ago! :laughing:

Still good advice, though.

I did!

Still have the same snow blower, too. :laughing:

 

[mrutkaus]

Same sort of wondering as above. New to me Woods Snowblower sb74-2.

Looking on line it appears that Woods has replaced an original un marked or un mark-mentioned-in-parts-list 1", 5/16" NC with a GRADE 8 same size bolt. So I don't know. Since they have 'updated' it with a harder bolt I'm assuming there is a reason. Perhaps the harder bolt is more apt to fracture?

Mike

 

[Rford]

Old thread I know, but I've got a Bush Hog Rhino that snaps those ungraded TSC 1/2 bolts like they were pretzels. Sometimes just a clump of grass will shear them and if the blade hits nearly anything they snap. I've been tempted to use grade 5 where a know its a pretty clean mow but, since I've got the bolt changing down to a science, I'm faster than the dad on "A Christmas Story" changing spare tires.

I was reading another post and it said that the problem might be not running the RPMs high enough. A slower RPM causes more shearing. That might be my problem, I'm probably on the slow side and maybe not even 1500 RPMS a lot. The post said when he went from 1500 to 2500 the shearing stopped. I'd never run mine up that high, but I might go up a bit and see if it helps.

 

[jwalk2c]

Old thread I know, but I've got a Bush Hog Rhino that snaps those ungraded TSC 1/2 bolts like they were pretzels. Sometimes just a clump of grass will shear them and if the blade hits nearly anything they snap. I've been tempted to use grade 5 where a know its a pretty clean mow but, since I've got the bolt changing down to a science, I'm faster than the dad on "A Christmas Story" changing spare tires.

I was reading another post and it said that the problem might be not running the RPMs high enough. A slower RPM causes more shearing. That might be my problem, I'm probably on the slow side and maybe not even 1500 RPMS a lot. The post said when he went from 1500 to 2500 the shearing stopped. I'd never run mine up that high, but I might go up a bit and see if it helps.

The problem I have with those TSC sheer bolts that come in the pack of 6 or so is they are not shearing no matter what RPM, or what I hit. I bought a slip clutch last year to ease my worries. I am running the sheer bolts on a 5 ft TSC bush hog and a FORD 1520 23 hp. I can hit a solid object that almost stalls the engine. The sheer bolts have to be drove out as they are bent but have yet to sheer off. Maybe I should try another pack? Strange but this is my luck always.
Thanks Johnny Walker

 

[kenmac]

I have no problems with the non graded bolts I but from HD, Lowes, etc

 

[topbuilder]

Old thread I know, but I've got a Bush Hog Rhino that snaps those ungraded TSC 1/2 bolts like they were pretzels. Sometimes just a clump of grass will shear them and if the blade hits nearly anything they snap. I've been tempted to use grade 5 where a know its a pretty clean mow but, since I've got the bolt changing down to a science, I'm faster than the dad on "A Christmas Story" changing spare tires.

I was reading another post and it said that the problem might be not running the RPMs high enough. A slower RPM causes more shearing. That might be my problem, I'm probably on the slow side and maybe not even 1500 RPMS a lot. The post said when he went from 1500 to 2500 the shearing stopped. I'd never run mine up that high, but I might go up a bit and see if it helps.

You should be running "PTO " rpms all the time with a brush cutter. It can wear on the clutch at too low a rpm as well.