I'm in the process of putting bolts in the places where i removed the rivets and such on the frame with grade 8 bolts. I also want to replace the rear cab and running board mount bolts too but can't find G8 fine thread bolts for them. I've tried all the hardware stores around as well as HD and lowes.... No luck, Would G5 be ok or does anyone know of a place that might have G8's in fine thread.

 

In California we have a place called Fastenal they carry alot of the different bolts. I got a 3/4 fine threaded left hand tap from them once and remember they had all kinds of hardware in the store

 

LMC Truck.com has those needed bolts. Don't know the grade. I know my ACE hardware has a large supply of bolts, including stainless. Aviation parts places have supplies of grade 8 bolts. In large cities there are bolt and rivit supply businesses. Have a great day,chuck

 

Grade 8 NF bolts should be available at your local parts house, although grade 5 would be sufficient for that application.

 

if you have a tractor supply co. near you they carry them

 

Grade 8 if it will leave a mark if it breaks
Grade 5 if you can pick it up on the way home.

 

Not a simple question.

Most people think the higher the grade, the better. Depends on the application. The grade is primarily the tensile strength. That being said, the higher the tensile, the more brittle..... It can clamp like a mother but it might not take a hit as well as a more "rubbery" (for lack of a better term) bolt.

So if shear is a concern, higher grade isn't always better.

Anyway, I suggest you replace with what's specified. Stay away from the local outfits like Depot of Lowes etc. It's crap. Aircraft and Speciality Fastener places that have to comply with ANSI standards is best.

Dawg-A-Roo

 

Very true. Grade 8 is fairly brittle compared to Grade 5 and that's not a desirable property on any bolt that sees shearing loads.

 

Sheer strength on a bolt is about 60% of the total tensile strength. A grade 5 bolt is about 120 000 psi and a grade 8 is 150 000 psi. You loose sheer strength on bolts over 180 000 psi this is where you get the brittle bolts. A grade 5 bolt will have failed way before a grade 8 bolt starts.

Go look at a farm equipment. They use shear bolts for protection of equipment. In many of the manuals it says to use grade 5 bolts and not to use grade 8 bolts or damage will result.

Just use coarse thread grade 8 bolts with lock nuts and you won't ever have a problem. Lock washers are useless.

 

Coarse Threads is correct. Need to bow to the smarter folks.

 

Ol'Henry used fine threads almost exclusively, and for good reason. They are much more resistant to loosening and can be torqued down tighter to begin with. Unless you want to crawl under there and tighten every durn bolt on the chassis every couple months, I would stick with UNF bolts, either grade, with locknuts, lockwashers, or LocTite 271. Use bolts from a reputable source, not the cheap chinese plated junk they sell at Home Depot, etc.

 

UNF engages more threads but the P.D. isn't as meaty. For a frame rivet replacement, I'd stay with UNC.

 

While fine thread is capable of of more torque and slightly more resistant to vibration but it also has some downsides too. It is more prone to thread type failures due to over torquing, rust/corrosion and cross threading.

Later Ford trucks used coarse threaded bolts on their frames with no problems. Look at many twin I beam trucks. It's just plain old bolts holding on the radius arm crossmember which takes the most abuse on the whole truck.

If Henry was so smart to use fine thread on the chassis so why does the Flathead V-8 not use ONE single fine thread bolt? I'd hate to try to remove 24 fine thread head bolts, as you would have to use heilcoils for some holes.

Let's face it we overbuild these trucks. Fine thread is overkill for our uses. Look at production vehicles, you won't find a single rivet on those frames and they see much bigger payloads then they did back then.

 

Thanks for the input and info guys!

If it wasn't for the nuts welded to the rear cab and running board mounts I probably would of put in G8"s but seeing thats theres not too much stress on them (except my big butt ) I should be ok with G5 on them? The rest are G8 ( Spring hangars , Front bed mounts and front cab mounts).

 

Grade 8 does have a higher tensile strength but since they are harder and more brittle I doubt that they will withstand as much shock load. On my front suspensions I always use grade 5 with no failures yet. I do use grade 8 where there is a possible wear factor. I only use the cheap grade 3 to hold on items where there is little stress and no safety concerns if it would fail. Grade 5 is 90% of my usage and cheap at Tractor Supply.