Grade 2 bolt ?

Status
Not open for further replies.
Joined
Nov 21, 2008
Messages
38
Location
Ohio, U.S.A.
I am wondering if a Grade 2 steel bolt(.75-10 x 4 3/4) is strong enough to be used to attach the front axle to the frame of a 4-wheel garden tractor?

I plan on mounting a 48 inch snow blower to the front of this tractor and do not want a bolt failure.

Thank you in advance.
 
It probably won't fail but if you really don't want to have a bolt failure and we're just talking about 1 bolt, spend the extra buck or two and get a grade 8. It is hardly worth doing a cost benefit analysis on a single bolt.
 
What is sold as SAE Grade 2 is often hardware store grade junk, not that grade 2 is very good any way.

You stand a better chance of getting a fastener that actually meets spec if you use grade 5 or better from a reputable source.
 
Stick with grade 8 it is bad enough so much Chinese garbage is not even true grade 8. Grade 8 will not shear it will stretch when it fails.
 
Oh boy. I purchased some "grade 8" bolts at NAPA. I thought they were good quality. But nearly every one of the half inch bolts broke in tension, holding on a generator head with very little load, but some vibration. I replaced them with stainless American made bolts and have had no problems.

Same thing with my Mazda Miata. I used NAPA bolts and they all failed. I should have learned the first time.

Anybody want to guess where my grade 8 bolts were made?????? Could it be a very large far East country known for "knock off products"??????? First letter is the third letter in the alphabet. Need any more clues?

In any case, grade 8 bolts are not the proper choice for a tractor. Grade 5 is. For durability and ductility.
 
Originally Posted By: JohnBrowning
Stick with grade 8 it is bad enough so much Chinese garbage is not even true grade 8. Grade 8 will not shear it will stretch when it fails.
Chinese garbage !!!YEP try to avoid anything important that is made in China if possible.
 
Originally Posted By: Michael_P
I buy @ Fastenal.


They are a great source as well and have retail stores in most cities. I've even had Fastenal make custom fasteners for me, for some old military hardware with strange threads.
 
This sounds like an app where they figured it'd be cheaper to use a huge cheap bolt than a smaller, tougher one. I bet a grade 5 will do. I bet you could hang the thing upside down from its axle with a grade 5.
 
years ago i worked for a co . that we mounted large elec motors and hyd pumps on a 1-1.5 plate. the first thing my boss told me was that we use grade 2 bolts. the reason? if something striped it would be the bolt, and the threads in the plate would be fine. the bolt cost a lot less than the plate.
 
Although a grade 3 or 5 would probably be stronger than the frame
steel that the bolt connects to, a grade 8 is best.
A grade 2 bolt is rated at 74,000psi
A grade 3 bolt is rated at 100,000psi
A grade 5 bolt is rated at 120,000psi
A grade 8 bolt is rated at 150,000psi
so no matter which you choose, it will likely be capable of sripping the threads in the plate
NEVER use bolts that don't have SAE grade marks since they can be of various quality and material.
 
Bolt quality is VERY easy to counterfeit. Its a matter of die marking. China is WELL known for this. Buy from a reputable source. John--Las Vegas.
 
We have (literally) thousands of electric motors on a power station,ranging from 0.25HP, to 12,000HP. the majority are mounted to base plates, and in 20 years I've NEVER seen a motor pull a thread out of a baseplate.

Maybe seen a handfull of ham fisted people strip a thread.

We've even made bolts into fusible links on couplings by machining them down and making them the weak link, but never seen them go either.

That being said, hardened chinese plasticine is scary for anything other than ornamental work.
 
Use a good grade 8 if you don't want the bolt to break. Ever. Grade 8's are usually yellow zinc-plated for corrosion protection too, which is a plus.

Grade 5 will probably be fine as well, but use one that is yellow zinc-plated for corrosion protection.

Fastenal and Tractor Supply are both good sources. Ace Hardware or Lowes are probably OK too. (My Tractor Supply sells Grade 5's that are green - very weird.)
 
Last edited:
Iagree with the others, I wouldn't bother with unmarked(less than grade5) The question is what do you want to break first, the bolt or what it's attached too? A grade 8 doen't generally break that easy,ie damage to associated hardware.
 
you my not beleave me but there are times you want a grade 2. a thick steel plate with a big oil pump bloted to the plate. why ? so if somthing goes wrong the bolt will break and not strip the plate or the oil pump. BUT this a call to be done by the engeninner.
 
Grade 8 bolts will snap like a toothpick with any impact load. They have great longitudnal strength to withstand incredible torque numbers, but snap like crazy if the load is transverse - across the bolt.

Alternately, a Grade 2 bolt will stretch like mad if you torque it too high, but will absorb almost all side impact laods without flinching.

I've seen the puzzled looks on the faces of "experts" who can't seem to understand why the Grade 8 bolt securing a pulley to a shaft through a cross-drilled hole keeps snapping with nearly no load.

Back to the original question, without knowing the orientation of the bolts and their loads I can't say for sure which is best to use. I am leaning towards the lower end, although not an ungraded bolt.
 
Status
Not open for further replies.
Back
Top