Grade of original bolts?

[06boblee]

Does anyone know the grade of the bolts used on these trucks- the ones headmarked "DPCD" ?

[just me]

I use Grade 5 as replacement hardware. Judging by how easy the Dodge Plymouth Chrysler Desoto bolts are to twist apart, they aren't very hard. And Grade 8, in my opinion, are too brittle in a vehicle that flexes as much as an M37.

[Kaegi]

the minimum to use is grade 5. I don't know what year the grading system came about but it was fairly late. the description of the stock bolts in parts lists say mild steel usually which is about equivalent to grade 5. I have not found stock bolts twist apart easily at all. in fact I have always been surprised at how many come part in good shape and can be re used. Jeeps on the other hand they seem soft.

[isaac_alaska]

the idea that grade 8 are too brittle and a grade 5 should be used instead is generally a myth. by the time a grade 8 has been stressed to deformation, a grade 5 has already broken. to test this you can put a grade 5 and a grade 8 in a vice and beat on them with a hammer and see which one breaks first. in the words of my shop teacher "use the calibrated whacker"

here is a good article that explains it.

If i remember right (and don't quote me) Charles mentioned that they replace most bolts with grade 8 when doing a rebuild.

[just me]

On my old Camaro race car, I would continuously break grade 8 bolts in my ladder bars every pass. I went to grade 5 and they would deform every race, but not break and loose the effect of the bar. I would rather the hardware deform instead of catastrophically fail. But, they are your trucks, your milage my vary and this has all the potential for the fun of an oil thread. Do what you want with your machines.

[MSeriesRebuild]

A premium quality grade 5 is rated at 150,000 PSI tensile strength. The same premium quality grade 8 is rated at 180,000 PSI tensile strength. Both deformation or breakage is bad news. Either is a catastrophic failure in my mind and would get my attention quickly onto seeking out the right fastener for that application. There is a reason why different grades are available, a specific type may work better in a given application. Harder is not always better. If you do the research on original DCPD logo bolts, you will come to the conclusion that they were simply ungraded, so who knows actually what they may be. From experience, they will strip / break easier than a grade 5 or grade 8. We stock only grade 8 fasteners in our bins, so that tells my general opinion. That however is not to say we don't buy some different types for specific applications.

[06boblee]

Thanks everyone for the responses. Just as an aside, the word "premium" does come into play when it comes to bolts. I got a batch of grade 8 bolts that would not torque properly- they would begin to stretch way before max recommended torque values. Turned out they were out of Japan and had not been properly treated. That is when I learned to read headstamps to find the origins of the bolts, you can find lists on the net.

[MSeriesRebuild]

Thanks everyone for the responses. Just as an aside, the word "premium" does come into play when it comes to bolts. I got a batch of grade 8 bolts that would not torque properly- they would begin to stretch way before max recommended torque values. Turned out they were out of Japan and had not been properly treated. That is when I learned to read headstamps to find the origins of the bolts, you can find lists on the net.

So true! That is why I included the word premium in my description. Our bins are stocked by Fastenal, a rep comes by every week, checks bins, reorders low quantity items and restocks the following week. We have had good luck with their products.

[Brigand]

https://www.google.com/imgres?imgurl=ht ... IQ9QEILDAA

Here's a handy little chart, there are quite a few available.

If you consult the chart you will see that grade 8 fasteners have higher tensile and shear strength. The key however is choosing the correct bolt grade for your application. there are engineering solutions that depend on the fastener failing instead of the part. In those instances when a part failure can cause structural cascade failure, a lower grade bolt may be spec'd for a particular application. At keast according to ASME standards.
For our application the stresses which cause shearing failure usually occur during collision where a bit of give on some components may reduce the stress suffered by the occupants.
That being said, for steering and frame repair I use grade 8 and grade 5 for non structural such as body panels.
Try and get your fasteners from a quality vendor. The off-shore stuff is not reliably graded and in some cases it is little more than pot metal.

[MSeriesRebuild]

https://www.google.com/imgres?imgurl=ht ... IQ9QEILDAA

Here's a handy little chart, there are quite a few available.

If you consult the chart you will see that grade 8 fasteners have higher tensile and shear strength. The key however is choosing the correct bolt grade for your application. there are engineering solutions that depend on the fastener failing instead of the part. In those instances when a part failure can cause structural cascade failure, a lower grade bolt may be spec'd for a particular application. At keast according to ASME standards.
For our application the stresses which cause shearing failure usually occur during collision where a bit of give on some components may reduce the stress suffered by the occupants.
That being said, for steering and frame repair I use grade 8 and grade 5 for non structural such as body panels.
Try and get your fasteners from a quality vendor. The off-shore stuff is not reliably graded and in some cases it is little more than pot metal.

Thanks for that correction, I was comparing grade 8 to grade 9 instead of 5 to 8 . Tensile strength of 5 is 120,000 PSI, 8 is 150,000 PSI. Grade nine or 180,000 PSI fasteners are considered the strongest commercial grade going by general specs. We do use these in some specific applications, mostly shear issues, never any problems to date.

[just me]

No matter what grade you choose, just don't cheap out with the Asia butter bolts. Using them just ends in tears.