newbie qustion on shear pins

[First one]

Ok, so as I'm learning just what and what not to do with my new tractor I sheared off a shear pin on the pto shaft . So
Off I go to get 10 more of them,the guy [John Deer dealer]
only had grade 5 bolts and the book said grade 4 he said it would be fine to use these instead . I would feel better to hear someone else say the same thing ,I sure don't want to break anything because of this . So would this be ok? Only a true newbie would ask this one. thanks

 

[whistlepig]

The difference between grade 4 and grade 5 bolts IMHO isn't enough to hurt anything. When you start getting in to grade 8 bolts is bad.

 

[Soundguy]

IMHO.. I'd use the oem grade shear pin or less.. not harder.. at least then when something breaks.. you can look at it and go.. darn.. guess the pin was just a lil too hard..

soundguy

Ok, so as I'm learning just what and what not to do with my new tractor I sheared off a shear pin on the pto shaft . So
Off I go to get 10 more of them,the guy [John Deer dealer]
only had grade 5 bolts and the book said grade 4 he said it would be fine to use these instead . I would feel better to hear someone else say the same thing ,I sure don't want to break anything because of this . So would this be ok? Only a true newbie would ask this one. thanks

 

[whistlepig]

Shearing a pin for me is very rare on my mowers and PHD. And when I do shear a pin I find whatever bolt will fit regardless of grade. I don't keep grade 8 bolts. They are expensive and wouldn't use a grade 8 for a shear pin.

 

[MikeD74T]

First one, You didn't say how you broke the shear pin. If it was your operating technique you may need to buy only two replacements. Two, because you should always carry a spare and fixing your technique will make a shear pin last for years.

For example,if you have electric engagement on your pto you should engage at idle speed. If it kicks out as many will per design, return to idle then reengage.
My Kioti also has auto engage/disengage when the 3pt drops/lifts. This can be hard on pins if done at rated speed.

Also do a search for slip clutch. Wonderful invention to protect tractor, implement, & reduce shear pin expense. Do the search rather than ask or you'll get a firestorm of conflicting opinion.

BTW, welcome aboard. MikeD74T

 

[Soundguy]

when I do shear a pin I find whatever bolt will fit regardless of grade. .

That kind of advice is why there are also threads on the reapir of tractors and implements here.

it's fine to abuse your own equipment.. but for the sake of other newbs reading these posts.. you shouldn't advocate installing higher grade shear pins than the manufacturer reccomends.. reguardless of if you get away with it or not.

soundguy

 

[Gary Fowler]

I found this site that has all the info you would ever need on bolts. I also search for shear strength and found a little on that. Without going into a complicated formula, it looks like shear strength is about 60-65% of tensile which is what most sites report. NOT too much info available on shear for SAE bolts.
SAE & ASTM Bolt Grade ID Marks & Properties Reference Table - Engineer's Handbook

 

[First one]

Gray Fowler,
Thanks for the Info. never really knew what Grade ment for bolts or shear pins . There is a big difference between one from the other, and I can see how important it is to use whats recommended .I wonder how many times someone has broke things by just grabing what they have on hand.

 

[ToadHill]

I think that if the pin is grade four and the bolt is grade five, that by the time you factor in the difference in actual diameter caused by cutting the threads into the bolt, you'll probably be almost the same.