? Is there anything stated anywhere what grade of bolt should be used for tow hooks Ive heard grade 8 will shear and grade 5 will bend before it shears I personly run grade 5 if thats what they send to mount a winch I figure its good enough but is it written in the bible somewhere recomendations?? :confused: :rolleyes:

http://www.pirate4x4.com/forum/showthread.php?s=&threadid=40342&highlight=grade+bolts

check it out.:D

Very good reading thanx Scott

well whats better scott???? i have grade5 but was going to change to 8.........i don't got hte time to read the other post, as i'm in school andnot even suppose to be on here at all........o well:D
thanks
-Mike

Originally posted by Rockrat
? Is there anything stated anywhere what grade of bolt should be used for tow hooks Ive heard grade 8 will shear and grade 5 will bend before it shears I personly run grade 5 if thats what they send to mount a winch I figure its good enough but is it written in the bible somewhere recomendations?? :confused: :rolleyes:

You need to look up the specs for Grade 5 and 8. I don't have it handy but it should be available somewhere. Confirm what is in that other thread, don't blindly follow it.

As a general rule, where possible put all connections in tension and use the largest Gr 8 you can get that will fit. In an ideal world you'd actually do the calculations to make sure you get it right...

TTBHBPW (Trying to be helpful but probably wasn't)

r@m

I gradiated frum both..

I is even a collage student now.

I is SOO smart!

A grade 8 bolt is considerably stronger than a Grade 5; it is stronger in both tension and shear. Keep in mind, that the higher the grade of steel, the less deformation it can take before it fails (less ductile). With bolts of equal size, a grade 5 will starrt to bend, deform and strain harden, then finally fail before a Grade 8 starts to deform at all. The only difference is, that when the Grade 8 fails, it will fail catostrophically with little or no warning, since it is comparitively brittle. The Grade 5 will bend and hopefully provide a warning first (but this depends on the type of load).

Grade 5 bolts are 36 ksi mild steel, and Grade 8 bolts are 46 ksi or 50 ksi (I can't remember which).

Grade 5 bolts are usually better in impact or high vibration use.

As far as winch mounting goes, four 1/2" Grade 5 bolts will take slightly more than 30,000 lbs. in shear before failure. That is more than enough overkill.

ok, what about for towhooks????? i think the holes are for 1/2" but not sure, is 5 or 8 better????? personally i wheel alot with Heeps, and they weigh alot more than a sami.......... i have 5 now but don't want any injuries from my hooks failing......sorry for butting into your tread scott but i'd like to ask this now:D
-Mike

1/2" Grade 5's are fine. That is what the tow hooks come with.

Each 1/2" Grade 5 bolt in single shear (i.e. tow hooks) is good for 7,000 lbs. in new condition. Two bolts for a tow hook are good for 14,000 lbs without any problems. It depends on what you are doing, but it is tough to get that much force on the bolts, and impossible with any normal winch. Also keep in mind that this is the point at which they start permanently bending and distorting. The bolts will actually start to bend at around 30,000 psi (5,890 lbs each) but they will spring back when you let off of them, they start permanently distorting at around 36,000 psi (7,050 lbs each), and they fail at somewhere around 45 to 50,000 psi (8,800 lbs. each or more). That is over 17,000 lbs for a tow hook. You will probably get your rig stretched into a LWB before you break that.

I have a 7,000 lb truck with a 10,000 lb winch and I use Grade 5's for the winch mount as well as tow hooks. I have moved some REALLY big trees that max'd the winch out until I got the snatch block out, and everything survived. If you are worried about it, you can always get the welder out :D

Thanx for all the replys it has been a long standing argument in tha club I personally use 1/2" grade 5 Fine thread on the tow points and 5/8" grade 8 on steering components my feeling is as long as there correctly torqued they sould never shear under
normal circumstances but that s my 02 thanx again Scott