Threads, Lubricants, and Torques: Home Mechanics Alert

[Elias40]

Not so sure of that Mr Elias. Brittleness is tempered out. Grade 8 is widely used in race applications and one gentleman on this forum was surprised I once mentioned grade 5/6 as he had not seen them in south. Usually grade 6 is bagged and sold in auto stores (three slashers). Also I think in open stock in H Depot and in the specialty drawers at Lowes. We all know to avoid plain, unmarked commercial grade bolts for blade retention, I hope.

Even though many are now saying "motoman, STFU!" I now think about a lot of archived material on metric, but you will really have to convince me you need it.

STFU? No, not in the least. You have the same right to bark as anyone else here. Take it from RED//GREEN We're all in this together. We can't possibly be right on everything. We went to a trade school; and one of the things stressed is that the 3 marks for 5 grade, or 6 grade, if you want, & 5 marks for 8 grade Coming from the groovy SAE boneheads, was to keep everybody, engineers included, in a deep state of confusion.

 

[Elias40]

Having spent 32 years in quality assurance for a major tractor mfg. I have never heard of a grade 6 bolt.

See, if we get input from those with enough sperience, thousand years or so, we might eventually be able to hit the target, even though the arrow is crooked, with target missing it's eye.

 

[Elias40]

Interesting thread. You've made me go back to my machinist training. First two websites will give you a basic understanding of bolt grading for the average engineer and consumer. These grades are standardized by the SAE (Society of Automotive Engineers). They are the most commonly used in the automotive and small engine industry. The last site shows a much more comprehensive chart and breaks the relatively SAE standards into a more precise and tighter ISO ( International Organization for Standards) standards.

You will see that there is no grade 6 bolt in the SAE standards and I assume that the bolts you are talking about (3marks) are grade 5. Don't really know about the grade of blade nuts, but in my opinion anything higher than grade 8, for this application, would overkill and possibly to brittle.

Bolt Depot - Bolt Grade Markings and Strength Chart

SAE Grades Steel Bolts

American Fastener - ASTM, SAE, and ISO Grade Markings

But, if the blades were installed en mass, They would use self-tapping 8 grade bolts, especially self locking, Driven by an air tool at it's maximum rated input 90psi, or so, They would tear everything up on the way in, and lock down tight. It may be the reason why we can't remove the bolts, as they sort become fused inside their nest.

 

[motoman]

Well since I have permission to keep babbling...I am at a disadvantage since my tractor pool is 1 (as in one). But the cub cadet nuts mentioned recently are puzzling . These are about the size of my Intek flywheel nut.? Why would a mfgr do that to a struggling homeowner ? And held in place by clamping? Maybe I should relent and praise MTD -Craftsman for the easy and reliable blade set up I have. This praise could undo a milligram's worth of frustration with the Intek. OK , craftsman,I praise you. :laughing:

 

[motoman]

But, if the blades were installed en mass, They would use self-tapping 8 grade bolts, especially self locking, Driven by an air tool at it's maximum rated input 90psi, or so, They would tear everything up on the way in, and lock down tight. It may be the reason why we can't remove the bolts, as they sort become fused inside their nest.

Self tapping grade 8...we could get Hercules to turn the lever arm.

 

[motoman]

See, if we get input from those with enough sperience, thousand years or so, we might eventually be able to hit the target, even though the arrow is crooked, with target missing it's eye.

I'm glad you did not mention a high count quiver magazine. Don't go there.:thumbdown:

 

[motoman]

Having spent 32 years in quality assurance for a major tractor mfg. I have never heard of a grade 6 bolt.

OK soulman, it seems I'm being over ruled. Where, oh where ,could I have got that one? Maybe an even number crept into my noggin , somehow. Thanks

 

[motoman]

QUOTE If you don't have a starting point on your fastener read the head marking .

**************************************************************
If both components aren't of the same grade I would think that point would be moot .

Mine will get lubricant every time and the lesser value. I just don't care for thread galling .:biggrin:

Some interesting facts in this link even though they are for stainless.

Stainless Steel Galling / Locking Up / Freezing Up

Thanks, sandbur. Good thread. Machining stainless is a bummer . A lot of carbide cutters used.

 

[motoman]

Having spent 32 years in quality assurance for a major tractor mfg. I have never heard of a grade 6 bolt.

My grade 6 bolt nightmare...am I losing it? Finally called Judge Judy who said "Never give up your dream...even if over ruled. " So ...see chart below. Last 2 sentences of text are what Elias told us.

 

[motoman]

Not so sure of that Mr Elias. Brittleness is tempered out. Grade 8 is widely used in race applications and one gentleman on this forum was surprised I once mentioned grade 5/6 as he had not seen them in south. Usually grade 6 is bagged and sold in auto stores (three slashers). Also I think in open stock in H Depot and in the specialty drawers at Lowes. We all know to avoid plain, unmarked commercial grade bolts for blade retention, I hope.

Even though many are now saying "motoman, STFU!" I now think about a lot of archived material on metric, but you will really have to convince me you need it.

Well since talking to Judge Judy and finding grade 6 really lives I must remain humble and correct the bagged- tagged remark. Three slashers grade 5, FOUR slashers=grade 6 which I never see either, but they live.