thrashingcows

I've been going crazy trying to find the flange head nuts and bolts.

But Think I finally found a guy who really knows his stuff. I told him what I was doing, and how I prefer to go over kill. He told me that Grade 8 bolts and nuts in this kind of application can actually be worse then using grade 5....since the grade 8 can crack and break due to flex. So He's bringing me in matched nuts, bolts and washers that are used in bridge building....so they will flex and still hold super strong.

mknittle

If there were enough movement to break a 1/2" grade 8 bolt the rivets would loosen. the only time I have seen breakage from flexing is on a stack of parts. say 3parts with a bolt that is maybe 2 or more inches long sort of like a shackle that doesn't have a brace.

I have been around class 8 trucks all my life(logging trucks mostly) And I can't remember the last time I saw a broken frame bolt." 6" long 5/8"motor mount bolts break much more often.

That said I do like the flanged bolts.

mknittle

Abbotsford sounds familiar Is it close to the Washington border?

patdaly

Grrade 8 would be fine in this application, but what he is referring to is ASTM A325 Structural bolts, and they will work just as well. No way would I trust my life with grade 5's in the frame.

They should be tightened properly, you also might want to bone up on the head markings so you know which type you are installing, Wiki has a decent article.

http://en.wikipedia.org/wiki/ASTM_A325

mknittle

Interesting comparison of SAE grade 8 vs SATM A325 from Portland bolt.

http://www.portlandbolt.com/faqs/gra...olts-compared/

thrashingcows

So you think I'm still OK to go with the ASTM nuts and bolts? They were not flanged head though. Nuts, bolts and washers sold as a complete unit.

mknittle

Like the link I posted said grade 8 are more precision. I would go with them.
Just my opinion.

j_martin

I've never seen properly sized grade 8 bolts fail when bolting frame or suspension components. you need to use the hardened washers also or the metal you're bolting will tend to tear as it would without washers.

I've seen 3/8 inch grade 8 bolts used to bolt on overload slap pads through rough rivet holes that should have been drilled to 7/16 or 1/2 inch fail, but that was not a proper application. It also was not done by me.

mknittle

A bit from my shaded past I made machined parts for James ***&Sons for close to 20 years. we built scientific testing machines.

http://www.hoskin.ca/catalog/index.p...uviaogvk7b53b4

NJTman

Glad you guys changed your mind about the gr 5 bolts.

Personally, I've snapped dozens of gr 5 bolts (by hand) as me strong like bull. My plow uses GR5 bolts, but they're designed to bend out of position in an overzealous impact. This way they can hold together the parts without damaging the truck frame and other parts attached.

I think others have used the GR 8 without incident, but personally, I would give them a quick tack weld on the nuts to the bolts to ensure they never back off..

mknittle

I humbly disagree on tack welding nuts. the reason being normal wear can occur between parts enough to cause loosening of the bolts. if welded there is no way to tighten(easily) them. I like Locktite 242 (blue)

NJTman

Point well taken,

Why not locktite red ? Or better yet, green ? Green supposedly will never come apart, and I've taken apart red fastened bolts before.

m-o-p-a-r

Here is my take on this subject (driven by about 20yrs of experience thanks to mother nature and her wonderful "rust-belt"):

I use 1/2" fine-thread grade-8, accompanied by grade-8 THICK washers, and grade-8 crimp-lock nuts (all-metal-lock-nuts).

A few details:

Not all washers are created equal. ACE sells nice thick grade-8 washers. But, they are in the specialty bins, and they don't ever have enough in stock. Another good source for thick hardened washers is your local heavy equipment dealer. IF! it has a friendly parts department. A lot of those are getting just as bad as auto-parts stores though. My go-to guy at the local CAT dealer retired, now I'm hosed unless I have a part#.

Whatever you do, do NOT use split lock-washers! They break in half, and fall out. I have seen it happen countless times. Whoever invented the split lock-washer was an idiot.

I too disagree with tack-welding the nuts. If for some reason the fastener ever does come loose, you will be cutting it off to replace. No fun, and unnecessary.

And lastly. You will have to check this stuff periodically. There is no way around it.

Project is looking AWESOME though!!! keep it up!

thrashingcows

The biggest problem trying to find the 1/2" fine thread grade 8 flange head bolts and nuts locally was the quantity they wanted to sell, and the availability. Most wanted to sell by the box...50-300...I only need 28. And almost every one said it would be 4-7 business days to get them.

These ASTM bolts I will have Monday morning...so I guess they will have to do. I will be loctite 242 blue on all of them.

I'll do a yearly check on them once I start driving the truck.

Thanks for all the great info guys...I appreciate all the different points of view.

gyman98

I agree with your choice of fasteners. Only thing I have to add is about the yearly check, with the blue loctite, moving it just a fraction with ruin the threadlocker. Best bet is to torque to spec then use the torque wrench when doing a yearly check or just do a visual or use a pry bar to check for looseness