Grade of Bolt

[bambamshere]

Does anyone know the Grade of bolt that is for the timing gear. Buddy says it is Grade 8 and I was saying I think grade 5. I snapped one today and it only was going to to 15 foot pounds. Pretty soft bolt. They are black bolt. 

 

Oh yeah it is the 3 bolts on upper gear for timing chain.  

[Radarsonwheels]

I think the grade is measured in tension not in shear? I thought grade 5 was less brittle and better for some applications since it will bend before breaking but I’m not any kind of expert. 

 

Sounds like you might have had a pot metal bolt in there! Hope it extracted easily and didn’t add a day to your thrash.

[kencombs]

What are the markings on the bolt head?  In most cases that will indicate the grade.  But, on older stuff it may not be marked.  3 dashes are gr5, 5 dashes are gr8.

 

As far as tension, not shear:  torque is tension.  The chain load when running would be shear.

 

Most important, there is no way to tell how many times it has been removed, replaced, retorqued or even changed in its' life.

[Don Coatney]

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Bolt Grade Markings and Strength Chart

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US Bolts
Head Marking	Grade and Material	Nominal Size Range (inches)	Mechanical Properties
			Proof Load (psi)	Min. Yield Strength (psi)	Min. Tensile Strength (psi)
No Markings	Grade 2 Low or medium carbon steel	1/4" thru 3/4"	55,000	57,000	74,000
		Over 3/4" thru 1-1/2"	33,000	36,000	60,000
3 Radial Lines	Grade 5 Medium carbon steel, quenched and tempered	1/4" thru 1"	85,000	92,000	120,000
		Over 1" thru 1-1/2"	74,000	81,000	105,000
6 Radial Lines	Grade 8 Medium carbon alloy steel, quenched and tempered	1/4" thru 1-1/2"	120,000	130,000	150,000
	Grade A325 Carbon or Alloy Steel with or without Boron	1/2" thru 1-1/2"	85,000	92,000	120,000
Stainless markings vary. Most stainless is non-magnetic	18-8 Stainless Steel alloy with 17-19% Chromium and 8-13% Nickel	All Sizes thru 1"		20,000 Min. 65,000 Typical	65,000 Min. 100,000 – 150,000 Typical
Metric Bolts
Head Marking	Class and Material	Nominal Size Range (mm)	Mechanical Properties
			Proof Load (MPa)	Min. Yield Strength (MPa)	Min. Tensile Strength (MPa)
	Class 8.8 Medium carbon steel, quenched and tempered	All Sizes below 16mm	580	640	800
		16mm - 72mm	600	660	830
	Class 10.9 Alloy steel, quenched and tempered	5mm - 100mm	830	940	1040
	Class 12.9 Alloy steel, quenched and tempered	1.6mm - 100mm	970	1100	1220
Stainless markings vary. Most stainless is non-magnetic.  Usually stamped A-2.	A-2 Stainless Steel alloy with 17- 19% chromium and 8-13% nickel	All Sizes thru 20mm		210 Min. 450 Typical	500 Min. 700 Typical
Tensile Strength: The maximum load in tension (pulling apart) which a material can withstand before breaking or fracturing. Yield Strength: The maximum load at which a material exhibits a specific permanent deformation Proof Load: An axial tensile load which the product must withstand without evidence of any permanent set. 1MPa = 1N/mm2 = 145 pounds/inch2

Shop for US Bolts
Shop for Metric Bolts

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C

[bambamshere]

It is Black with a F on the head. I bought a bunch of Grade 5 bolts last night. But I will see if I can get Grade 8. Oh and the only marking on the top of head is that F

[DJ194950]

That " F"  stands for the Chinese word - cheap trash! Just my guess.?

 

I would never use anything less than a marked grade 5 on my vehicles. Grade eights are made for high stress- pull wise, not shear were primary to the job. Some jobs really require that bolt to stretch, bend, etc. resisting outright breaking.

 

Just one opinion!

DJ