Bolt Grades

[BOBWOOD]

I am just replacing my track rollers and was wondering if it is OK to use grade 8 bolts in them and the rock guards? I have already purchased them...but a guy at work told be to use grade 5 as the others are too brittle and will break....Also, to confuse things I was just reading a posting on another site and everyone advised the guy to use grade 8...BOB

[digitup2]

I find that grade 5 will loosen off so we use grade 8 on roller flanges and rock guards they tend to stay tight longest .Digitup,

[BOBWOOD]

OK...thanks for the advice...I'll go with what I've got then....I'm not too experienced at mechanical stuff...usually just bring the broken stuff to my brother and father who are both mechanics...I will have to be sure not to assume things...like a grade 8 being better than a grade 5....sounds good but it is not necessarily true in all circumstances....BOB

[Tigerhaze]

I would put a lot of weight on Digitup's advice- he puts thousands of hours on these machines commerically.

[mini kahuna]

use grade 8,5 with not hold up to the abuse.
I like to use theadlocker as well,use stuff that is removable with tools.

[JWB Contracting]

On our wide pad 350's we weld most of the bolts in, rollers, rock guards, cross memebers. Front cross memeber and track frames are also welded. We do start out with all new high quality bolts and everything gets rethreaded or drilled and tapped out larger if necessary.

We have two loader widepads equiped with angle dozers and 9550 hoes and have been in service since the early 80's. I would say they have held up very well to extreme use.

We have found this is the only way to make sure that they don't come loose. It does take a very long time when you need to dissassemble but well worth it. For us, we cannot afford to have any breakdowns during the short summer construction season here in Alberta. Trick is to weld in a spot that you can easily grind. We did a complete strip our our 450C dozer widepad this winter and it did take a long time to dismantle. However, the repairs that we did had to do we a broken front crossmember (split at the dozer mounting hole) and not because any bolts came loose. We fixed it up with a few pieces of 3/4" T1 plate on each side, so hopefully it will hold for a while.

[Jack-the-Ripper]

My understanding of the different bolt grades is that those with the higher numbers have higher tensile strength, meaning that if you are trying to separate the bolt (have it "fail in tension") by pulling it by its ends along its length, the higher grade will take more pounds per square inch before failure (also called the "yield point"), or another way of saying it, for the same diameter bolts, the higher grade will withstand more pounds of pull before it breaks.

Compare welding rods for a moment. A 6013 has a steel rod core with 60,000 psi tensile strength, whereas a 7024 has 70,000 psi tensile strength (I don't know if that is working strength or "yield" (i.e., failure) strength but you get the idea.) The 13, or the 24 denotes the composition of the flux coating on the rod and designates its other usage properties. So what does that tell you about 6011 or 7018? Which would you prefer to use when welding up a crack in your dozer frame: 60xx or 70xx?

Now think of a sheet metal screw or a "Grabber" sheetrock screw originally intended expressly for self-drilling into steel wall studs. These screws have to be harder, especially at the threads, than the steel into which they are expected to drill and tap. They are "case hardened" meaning that their outside layer (or case) is hardened, which also leaves them brittle.

Now lets think of sledge hammers and crowbars. They are tough (high compressive strength) as well as having high tensile strength. They don't mushroom over when repetitively struck (ie, they are not maleable). However neither are they brittle. "High speed steel" (as for twist drills) and "Tool Steel" need to be hard and tough enough to cut other steels without breaking, the same with taps and dies (yet they seem to be prone to breaking and thus assumed to be brittle.

Often a higher strength bolt is not necessary, perhaps as when assembling wood. Sometimes the extra cost of the stronger bolt is not justified. In general, however, I would say that anything with a John Deers logo on it will always benefit from the higher grade bolt and I can't think of any detrimental side effects from using grade 8s.

There is one exception where John Deere implements, and many others may be harmed by a higher grade bolt, and that is where the bolt is intended for use as a "Shear Pin," meaning a controlled point whose failure is intended to prevent damage to other more expensive parts. The bolts that hold the augers to their shaft in a snow blower readily come to mind. They prevent damage to the drive train when the unit hits a large rock.

So there are many ways of alloying iron with other elements, and then heat treating the resultant steels, to provide many different properties. I hope this analysis makes the grade.

[Tigerhaze]

We had a couple interesting discussions in the past about bolt grades for Deere equipment:

http://www.jdcrawlers.com/messageboard/ ... lt&start=0

http://www.jdcrawlers.com/messageboard/ ... grade+bolt

[MattE]

I have found that Nord-Lock brand washers will solve this problem. Still use grade 8, but it virtually eliminates the bolts backing out when torqued properly.

You can get them through mcmaster

[BOBWOOD]

Thanks for all the informative replies...I will certainly stick with the higher grade for sure...My dad, who worked for the local CAT dealer most of his life, said all CAT bolts are grade 8...

[440 iron popper]

all CAT bolts are grade 8...

Yes that's right. In safe source book's hardware section, you have all sizes bolts, nut, flats, locks name it. Here is the link (click harware reference at the bottom). You'll find out a lot of usefull parts in there:

http://www.cat.com/parts/hardware

Every bolts used in my 440 rebuild will be Cat, exept head bolts and other special ones...