to grade 8 or not...

[ggdad1951]

...that is the question.

in startign to reassemble I've been told use grade 8 bolts, I've also been told not to...what have you guys done?

Grade 8's are much harder, but more brittle....and more expensive!

[TodFitch]

My take (you will probably get as many opinions as for oil or brake fluid):

1. Bolts fasten things together by being slightly stretched. To slightly stretch a grade 8 bolt takes more torque/force than for a grade 5. And both take more force to stretch than a "common" un-graded bolt.

2. The engineer who designed the part specified the number and size of fasteners based on the clamping force desired. And, of course, on what was available to the factory in high enough volume.

So if you use the same grade hardware that the factory did for the application you should be just fine.

If you "up grade" your bolts, you should be careful that the torque required to properly tighten them is not too much for the parts being clamped together. In most cases I think going for grade 8 is overkill and I can imagine some cases where parts warpage could result.

[jakenoklahoma]

depends on where you want to put them. You dont need gr 8 on fender bolts, but they can be helpful on certain applications. you can get grade 8 fairly reasonably priced at Tractor Supply, by the pound.

[ggdad1951]

well I can get grade 8 for a even better price thru my work discount at Fastenal...I just think that 8 might be a bit overkill in most of the locations in the truck such as:

transmission brace

motor mounts

shock mounts

bed braces

etc....

I think grade 5 would do just as well, if not better having a bit more give/stretch....

[Young Ed]

I would use grade 5 for all the locations you mentioned with the possible exception of the motor mounts. I must ask for some of these why you are not just reusing what was there? I'm still using my original motor mount bolts I believe they are cross drilled for a castle nut and cotter pin arrangement. I did use grade 8 to reattach my running board mounts and the spring hangers I had to unrivet from the frame. I also ended up using them for my clutch cover of all places but that was because they only had that size/thread in grade 8 at the store at that time.

[HanksB3B]

Not talking engine or mechanical assembly. I had all my original bolts cad plated and re-used most of the larger bolts (like motor and cab mounts). When I started to assemble things I switched to all stainless for most of the non-critical assemblies 1/2" dia and under. I liked the look and feel of how they went into various original clips and tapped holes, Not to mention that they will never rust. I did use grade 8 to attach the doors and didn't like the way they felt going in (too brittle and unforgiving) and don't particularly like the look either. Someday I will switch them out for stainless.

Grade 8 is way expensive,

Hank

Edited September 3, 2010 by HanksB3B

[ggdad1951]

I would use grade 5 for all the locations you mentioned with the possible exception of the motor mounts. I must ask for some of these why you are not just reusing what was there? I'm still using my original motor mount bolts I believe they are cross drilled for a castle nut and cotter pin arrangement. I did use grade 8 to reattach my running board mounts and the spring hangers I had to unrivet from the frame. I also ended up using them for my clutch cover of all places but that was because they only had that size/thread in grade 8 at the store at that time.

well, honestly, becuase my friend who is helping me thinks its a good idea and I'm too new to this whole deal to know better. I'm a woodworker at heart and this is all so foriegn to me, hence my unending littany of questions. I'm actually starting to think I should just replace the lock washers, use the old bolts and nuts (where they are in good shape) and just me done. My friend feels that since it is down to the frame it's best to replace all the fasteners.

[Young Ed]

I agree 100% with your new washers and reusing old bolts that are in good condition.

A woodworker huh? Have you seen my thread on the car side about building a new kitchen cabinet? I'll be Pming you if I get stuck on a project now

[ggdad1951]

no problem! I've been doing wood for 30+ years now and that is how I'm paying for this, er, insanity of a project with wood side projects. I haven't ventured to far over on the car side...might have to mosey over there!

[Bob_Koch]

Larry Lyles did a nice write up about bolts in the Sept issue of Auto Restorer. Before the 60's almost all bolts were at least grade 5, except some fender bolts. Grade 8 were used when the application specifically called for it. No reason mentioned why you can't use a grade 8 instead of a 5 except the expense. Be sure to match it with the same grade nut and washer.

[Dave72dt]

Most of the fasteners on farm equipment are grade5 and they get a tremendous amount of abuse without failure, more than you'llever give it driving it on the road. Grade 8 to fasten spring hangers if they've been removed,( you're dealing with some shear factors instead of stretch factor) grade 5 for everything else will be more thasn adequate. Yes, replace the lock washers, fasteners with worn, galled or stretched threads. In case you didn't know, most of the nuts used on bolts are at least one grade lighter in strength than the bolts so the nuits strip before the bolts.

[ggdad1951]

any issue with using a "high alloy" (read grade 8-esque) lock washer with the old nuts and bolts?

[Frank Elder]

To me once a lock washer that has been flattened, it is comprimised, nuts don't stretch as much as bolts so I think their integrety is solid.

2 cents only.

As always follow the manual.

[JBNeal]

fastener selection is a balancing act with the materials that are being assembled, as you would want the critical parts to stay intact and have fasteners fail first. I haven't tested the Dodge frame, but I figger it's about 36ksi material. Any grade 8 bolt's hardened surface would deform the 36ksi material before the bolt would shear. Grade 8 would definitely eat through sheet metal, and more than likely would shred door hinges after several thousand cycles. Zinc-plated grade 5 bolts should be adequate. Definitely use new lock washers where applicable.

On a related note, there are several areas where fine threaded bolts are used. Unless the fine threaded bolts screw into a tapped hole, they can be replaced with coarse threaded bolts with lockwashers or locknuts.

Flat washers should be chosen based on the bolt grade. Fender washers are usually softer than regular hardened washers as they are used to distribute the fastening torque over a larger area, kinda like snow shoes or flotation tires distribute weight over a larger ground area. Hardened washers have a slight cup to them, making them act like helical spring lockwashers, but I don't recommend using them in place of standard SAE flat washers as the hardened washer may bite into the base material.

And then there are the rivets in the Dodge frame. By their nature, they are slightly harder than the frame material. And they do not make for a tight fit over time, so the aging rivet is a source for wiggles & squeaks in any old beast. I have some frame issues on my '48 that require a complete tear-down of that ol' farm truck, and I will be performing some strategic welding to address that. I will also do a little reinforcement in the rivet areas to stiffen up those areas, which should have the added benefit of giving a unified ground source for the electrical system.

[ggdad1951]

fastener selection is a balancing act with the materials that are being assembled, as you would want the critical parts to stay intact and have fasteners fail first. I haven't tested the Dodge frame, but I figger it's about 36ksi material. Any grade 8 bolt's hardened surface would deform the 36ksi material before the bolt would shear. Grade 8 would definitely eat through sheet metal, and more than likely would shred door hinges after several thousand cycles. Zinc-plated grade 5 bolts should be adequate. Definitely use new lock washers where applicable.

On a related note, there are several areas where fine threaded bolts are used. Unless the fine threaded bolts screw into a tapped hole, they can be replaced with coarse threaded bolts with lockwashers or locknuts.

Flat washers should be chosen based on the bolt grade. Fender washers are usually softer than regular hardened washers as they are used to distribute the fastening torque over a larger area, kinda like snow shoes or flotation tires distribute weight over a larger ground area. Hardened washers have a slight cup to them, making them act like helical spring lockwashers, but I don't recommend using them in place of standard SAE flat washers as the hardened washer may bite into the base material.

And then there are the rivets in the Dodge frame. By their nature, they are slightly harder than the frame material. And they do not make for a tight fit over time, so the aging rivet is a source for wiggles & squeaks in any old beast. I have some frame issues on my '48 that require a complete tear-down of that ol' farm truck, and I will be performing some strategic welding to address that. I will also do a little reinforcement in the rivet areas to stiffen up those areas, which should have the added benefit of giving a unified ground source for the electrical system.

all makes perfect sense. I plan on re-using the old parts 'cept the lock washers and flat washers, degreasing and etching them all so the POR15 has a good bite and seal....

:confused:so again, since this hasn't been answered: can I use the "high alloy" lock washers or should I stick to the softer ones?

[JBNeal]

high alloy helical spring lock washers will carve into 50ksi steel when enough torque is applied on a bolt/nut to flatten it. High alloy lock washers are to be used with Gr.8 bolt/nut & washers; using them with Gr.5 bolt/nut & washers is an 'imbalance', as the lock washer will carve into the bolt/nut & washer before final torque is applied.

[Harvey Tank]

I might be wrong, but I thought in automotive we use grade 5 only.

[ggdad1951]

high alloy helical spring lock washers will carve into 50ksi steel when enough torque is applied on a bolt/nut to flatten it. High alloy lock washers are to be used with Gr.8 bolt/nut & washers; using them with Gr.5 bolt/nut & washers is an 'imbalance', as the lock washer will carve into the bolt/nut & washer before final torque is applied.

ok, so....anyone want some high alloy washers?!?? I got a box of each for several sizes... I got the high alloy washers to go with the grade 8 bolts I got...I got a few of them as well...

SOOO glad I found you guys! thanks again!