# What does this symbol mean?



## TomB985 (Dec 21, 2013)

Hi everyone,

Does anyone know what the symbol on the head of shear bolts means? Is it some form of grade marking?


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## Snapper 524 (Dec 10, 2013)

It is probably just a manufacturers mark. Shear bolts don't usually have grade markings.


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## Toro-8-2-4 (Dec 28, 2013)

I concur with Snapper. It is a manufacturers symbol.


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## TomB985 (Dec 21, 2013)

Okay then, which manufacturer is it?


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## Zavie (Sep 23, 2014)

I'll handle this one.


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## Toro-8-2-4 (Dec 28, 2013)

It is just not a symbol that represents any common grade standard. I took a quick look at my bolt grade charts and nothing close to it was there. It is not from a nuclear power plant or air plane so it is safe to say it is a manufacturers mark. It is not that uncommon for a manufacture to put their own symbol on the head.


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## JnC (Feb 21, 2014)

Usually any sorts of marks on the bolt heads indicate the tensile strength but thats usually true for imperial/standard fasteners. 

I was curious about the markings as well and the explanation that I got from someone once was that the " Ø" symbol refers to the cross sectional diameter. The bar next to the symbol is the actual diameter. 

I am not sure how true that statement is but it made sense.


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## tinter (Apr 20, 2014)

It appears to be the O.E.M. symbol on Honda shear pins. It was driving me foolish, I knew I had seen this symbol before. Went to the garage and there it was. Also went on eBay and did a search for Honda shear pins. Maybe a Honda trade mark?


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## dhazelton (Dec 8, 2014)

That marking indicates that the bolt costs $3.49 at the Honda dealership. And the corresponding nut will cost 99 cents. I keep telling myself I'll plan ahead and get a bunch on eBay but never do.


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## Toro-8-2-4 (Dec 28, 2013)

I had a friend who use to make his own from a 1/4-20 bolt grade 2 bolt. He had a lathe and would turn a groove in it to mimic that of the pins on his machine......... He did not have a Honda. I think he had some kind of MTD machine.


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## Toro-8-2-4 (Dec 28, 2013)

Just an FYI.

I was in my shed looking at some spare parts and noticed a "SP" marking on the head of MTD shear bolts.

SP for shear pin maybe? I assume they mark them to make sure no one (in the factory or elsewhere) confuses them with a conventional bolt.


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## TomB985 (Dec 21, 2013)

Just answered my own question. Must be a manufacturer symbol. 

Yesterday I was installing a winch on my mom's new Honda Pioneer and noticed the suspension bolts had the same marking on the heads. These are most certainly NOT shear bolts! 



I doubt Honda makes their own fasteners, so it may be their supplier's marking of some sort. Or perhaps that the bolts are engineered specifically for Honda?


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## dhazelton (Dec 8, 2014)

If SP meant anything it would probably be in Japanese anyway.


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## TomB985 (Dec 21, 2013)

dhazelton said:


> If SP meant anything it would probably be in Japanese anyway.


Probably not on MTD parts.


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## Kiss4aFrog (Nov 3, 2013)

I don't think there is enough room on the head of those bolts for it to be bi-lingual.


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## Fasted (Feb 11, 2015)

That is a Honda number "8" bolt. I restore Honda motorcycles and the bolts had the "8" in the 1960's and slowly the symbol morphed into what you see now. Here is a picture of the older style Honda bolts. Old style "8" bolts like this sell for a lot on eBay!


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## Fasted (Feb 11, 2015)

See:

1969 Honda CB750 Four K0 034 8 034 Mark Bolt Set Sandcast New S030 | eBay

ED


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## wdb (Dec 15, 2013)

Honda brand bolts! Kind of expensive but nothing like some bicycle parts:


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## db9938 (Nov 17, 2013)

Fasted said:


> That is a Honda number "8" bolt. I restore Honda motorcycles and the bolts had the "8" in the 1960's and slowly the symbol morphed into what you see now. Here is a picture of the older style Honda bolts. Old style "8" bolts like this sell for a lot on eBay!


Does the 8 refer to it's grade, by chance?


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## TomB985 (Dec 21, 2013)

Wow. Some folks pay a LOT for a symbol. 

So...who makes these Honda brand bolts? Are they made in house? Noticed the OEM shear bolt for the impeller has no marking on the head.


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## Toro-8-2-4 (Dec 28, 2013)

TomB985 said:


> Wow. Some folks pay a LOT for a symbol.
> 
> So...who makes these Honda brand bolts? Are they made in house? Noticed the OEM shear bolt for the impeller has no marking on the head.


 Just for my own understanding what was the bolt in the original picture you posted use for if not an impellar shear bolt?


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## TomB985 (Dec 21, 2013)

Toro-8-2-4 said:


> Just for my own understanding what was the bolt in the original picture you posted use for if not an impellar shear bolt?


That was the auger shear bolt. The impeller shear bolt is completely different and looks like this:


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## PracticalProgram (Jan 12, 2014)

Some thoughts on this . . . and I am sure it has been covered on a 100 other threads . . .
If you look at the eBay listing that Fasted posted, there is a reference to "MC Yamiya" as the part brand.
If you Google "Yamiya", you find a number of motorcycle supply houses marketing Yamiya hardware, and their verbiage implies that it is Honda OEM hardware.
But regardles of whether the mark is a brand mark, or a rating mark, I don't think anyone should base their shear pin/bolt selection based upon an interpretation of that mark.
In my mind, the first thing that should break on your snowblower are the auger shear bolts. The second thing that should break is the impeller shear pin. And the last thing that should break is your transmission.
Following that line of thinking and working back from the transmission, there is very little any of us can do to strengthen the transmission, so let's move on to the impeller shear pin.
The impeller shear pin is a custom screw-machine part that is obviously designed to shear at a particular force, or impulse. I would not second-guess Honda's engineers as to the design of this piece, and very few of us have a lathe at home to be able to make our own, custom, impeller shear pin. And besides, you wouldn't want to strengthen it 'cause that will just pass the load on to the transmission. Bottom line, we've not going to do anything with the impeller shear pin.
That leave us with the auger shear bolts.
To me, the auger shear bolts should be selected to that they are always the first thing to fail.
How do we do that? We can buy shear bolts that are made of the lowest yield point materials, but not so low that we spend half our snowblowing time replacing shear bolts.
In the US, it is very difficult to find metric M6 bolts graded anything less than 8.8 (there are, apparently, 4.6, 4.8 and 5.8 gradings). So we are stuck with using 8.8 auger shear bolts.
Or are we?
All of those ratings apply to carbon steel bolts.
So what I've done is switched to is stainless steel bolts.
Stainless steel is generally about 2/3rds of the yield strength of carbon steel.
I've been using SS now for about nine years, first with an HS928 and now with a HS724.
In the nine years, I've ingested Sunday New York Times buried in the snow, garden hoses, etc. and never have had to replace my impeller shear pin, just auger shear bolts.
So, my recommendation is to try stainless steel auger shear bolts.


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## TomB985 (Dec 21, 2013)

I like your logic Practical, thanks for the input. I've gone through about a dozen auger shear bolts this season, but my driveway is gravel with the occasional large rock that gets stirred up by the plow. I've broken two impeller shear bolts. 

Since the symbol is on suspension fasteners on a Honda all-terrain vehicle it's safe to say the marking has nothing to do with grade.


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## Toro-8-2-4 (Dec 28, 2013)

TomB985 said:


> That was the auger shear bolt. The impeller shear bolt is completely different and looks like this:


 
Again for my understanding. Does the impeller shear bolt shown in the original post have any grooves cut in to it to weaken it? Does it have a full thread?


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## TomB985 (Dec 21, 2013)

Toro-8-2-4 said:


> Again for my understanding. Does the impeller shear bolt shown in the original post have any grooves cut in to it to weaken it? Does it have a full thread?


It has a full thread. Outside of the symbol on the head it looks just like any other bolt.


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## tabora (Mar 1, 2017)




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## Toro-8-2-4 (Dec 28, 2013)

A manufacturer can put what ever symbol or markings they want on the head of a bolt. As long as they are not implying something that is not true. If they want to meet an standard they need to follow whatever that standard states. Here is an example of ISO 898 for metric bolts.






Metric Steel Bolts - Grades and Property Classes


Metric steel bolts, screws and studs - proof and tensile strength.




www.engineeringtoolbox.com


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## RC20 (Dec 4, 2019)

You certainly can put that in the shear pin slot, does not mean it shears the same


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## RC20 (Dec 4, 2019)

_All of those ratings apply to carbon steel bolts.
So what I've done is switched to is stainless steel bolts.
Stainless steel is generally about 2/3rds of the yield strength of carbon steel.
I've been using SS now for about nine years, first with an HS928 and now with a HS724.
In the nine years, I've ingested Sunday New York Times buried in the snow, garden hoses, etc. and never have had to replace my impeller shear pin, just auger shear bolts.
So, my recommendation is to try stainless steel auger shear bolts._

Your post was good until you got into your view. You are making an opinino based on very bad factual reality if not totally off the wall. 

There is nothign changeling shear wise to a newspaper or a garden hose. I in fact ran a newspaper through my Yahmah a few weeks back and it was like nohting (you really think a newspaper or a hose is worse than a chunk of ice?)

Graded hardware such as 2/3/5/8 as well as its metric equivalents are based on tensile not shear.

Honda has an *S *on their shear bolts, nothign more, noting less (the carriage shear have nothign on them).


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## RC20 (Dec 4, 2019)

_Again for my understanding. Does the impeller shear bolt shown in the original post have any grooves cut in to it to weaken it? Does it have a full thread? _

You do the shear function with materials and treatment.


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