Shear pin?

[Von]

Jag, I don't think you want to spray oil on any dry clutch. It would cause the clutch to not grip therefore slipping and in effect not work.

[GlueGuy]

BMW,

Go with John's advice, use the grade 2 bolts. You want the bolts to blow, not your equipment. Kinda like a circuit breaker in an electrical circuit: you want the fuse to blow before the wires melt (or catch fire [img]/w3tcompact/icons/shocked.gif[/img]!!!).


The GlueGuy

[Bird]

<font color=blue>Go with John's advice, use the grade 2 bolts.</font color=blue>

Amen!

Bird

[MarkJC]

Just so everyone is clear, a grade 5 bolt has 2 lines on it. A grade 8 bolt has 5 lines on the head strike. A bolt without lines on the head strike is buyer beware, you don't know what you're getting, but it's probably soft, so it would have a lower shear strength than a higher grade bolt. The difference in grading primarily relates to tensile and shear strength and is derived from different alloys and heat treat processes. A properly designed shear pin protected drive train should have the shear pin fail as the first line of defense to damage, using a higher shear strength bolt puts the whole thing at risk for damage.

[Jag]

Von, just a light shot to keep the rust away... What is best, slip to soon or slip to late...

[TWINKLE_TOES]

Just to make it clear'er[img]/w3tcompact/icons/smile.gif[/img]

<font color=blue>a grade 5 bolt has 2 lines on it. A grade 8 bolt has 5 lines on the head </font color=blue>

This is from Thomas J. Glover, pocket reference on bolt grades.

SAE Grade 0 -1-2 no lines
SAE Grade 0 -1-2 no lines
SAE Grade 0 -1-2 no lines
SAE Grade 3 two lines
SAE Grade 5 three lines
SAE Grade 6 four lines
SAE Grade 7 five lines
SAE Grade 8 six lines

Please note that just because a bolt is grade 2 does not mean
it will break easily. Grading only refers to the minimum strength, not the maximum. Thus, if a machine uses a soft bolt as a safety shear pin, and you happen to replace it with a grade 2 bolt that was actually manufactured to grade 8 specs (but was marked down because too many of the bolts in the lot failed, so the whole lot was marked down) you could create some serious problems. Replace safety-related items
with proper stuff! Also beware of improperly-marked forgeries.

Al

[Von]

Jag,
But what if you now have constant slipping and have to buy new clutch packs? I still say no oil on dry clutchs with no exceptions! Unless you have money to burn on new parts every year. You are better off removing the pressure on the clutch pack so that rust will not be a problem.

[hayden]

Or for those of us who are memory impared - the grade is the number of lines plus 2.

[ddl]

Question: Is not the bolt markings molded into the bolt head when the formed? If so, how can a grade 8 be changed to grade two when bolt fails specs? Am I missing something?

Dan L

[RJohnson]

The grade designation comes from the automotive industry, their specification SAE-J429. There are ASTM standard bolting specifications that have compairable bolts. The problem with the two standards is that the marking requirements are different. An SAE Grade 2 for example has no markings, it also has two different strenght levels depanding upon the diameter of the the bolt. For 1/4 through 3/4 the bolt has a 74,000 psi tensile strength as a minimum, over 3/4 through 1 1/2 the tensile strength drops to 60,000 psi. The ASTM A307 is a compairable bolt (with no markings) but its minimum tensile strength is 60,000 psi no matter what the diameter. This is exactly like MarkJC stated, you don't know what you are getting and with a minimum tensile strength specification you can end up with bolts of the same grade with drastically different mechanical properties. I am going to scan a bolt head identification chart and will try and post it tomorrow.

Randy