When your handlebar is too tough to bend...

[russ69]

Just an FYI, metric grade 8.8 is close to SAE grade 5. What you are seeking is grade 10.9. Tough to do with socket head screws. That being said, well done on getting home.

A high grade screw is nice but you are screwing into aluminum so a grade 8 screw will just pull the threads out. That is why in aircraft design you have to use an insert when screwing into aluminum. A low grade screw will work fine in aluminum. Any Allen brand screw is way more than enough.

 

[russ69]

...

Fatigue.

 

[corndog67]

For the curious, here's a photo of two of the old broken off bolts and one of the new ones that I did some grinding and rustproofing on so that it would fit. I only ground off enough metal to get it to mostly fit, but the bars still touch all of the new bolts just slightly. On the bolt in front you can see the bottom of where the Allen wrench would touch. As I said earlier, I'm surprised they held the bars on as long as they did.

Generally, those button head screws have a smaller allen key size than a standard socket head cap screw (like a 6mm hex vs an 8mm). And that is kind of a safety feature against overtightening them, the hex in the screw itself will usually round out before you damage the threads or the screw. Those socket head cap screws you replaced them with will be real easy to overtighten with a 8mm allen wrench. Loctite, snug em up, plus a little, since most people won't be carrying a torque wrench out on the trail.

 

[Charles R]

Fatigue.

Yep. Bolt looks like the fatigue crack was about 50% through when you dumped it and it broke the rest of the way.

As a side note... The harder/stronger a metal is, the more susceptible it is to the growth of fatigue cracks.

 

[louemc]

As a side note... The harder/stronger a metal is, the more susceptible it is to the growth of fatigue cracks.

Umm, depends. The words "metal", "harder", "stronger".. are too un-defined. And the application isn't stated either. Radius vs sharp angle corners, isn't defined...

Tool & die makers deal with Hard (wear resistant) dies hammering parts to a shape, in punch presses... All the time.

 

[louemc]

Fatigue.

And the fatigue is because those screws were junk.

 

[SFSV650]

There was enough of the broken screws sticking up to hold things in place as long as I continued to push down rather than pull up. Heading back up that rocky road would have been difficult with unbroken bars....

Is this a case where a couple of zip ties would have been infinitely better than nothing? Throw a couple of those into the adventure case with you, eventually you'll be glad you did.

 

[Charles R]

Umm, depends. The words "metal", "harder", "stronger".. are too un-defined. And the application isn't stated either. Radius vs sharp angle corners, isn't defined...

Tool & die makers deal with Hard (wear resistant) dies hammering parts to a shape, in punch presses... All the time.

Definitely too vague for anyone in the business, but a worthy statement for the average joe who might think, "I want stronger bolts!" Without knowing there may be trade offs involved.

These days, the level of engineering and manufacturing quality afforded to your average, "over the counter" bolt also makes it a quality statement.

You're right... But we are talking apples to oranges here. The whole topic here is broken bolts. We are talking about bolts. Over the counter bolts as well.
Bringing in an example dealing with punch press tooling is like bringing in a linebacker as your pinch hitter.

 

[OaklandF4i]

I'll second a previous poster's word of caution about over tightening these stronger bolts in your aluminum triple clamps. I'm not a pro or an expert machinist.

I like my forks, triple clamps, bars, levers etc to twist in a crash, not bend or break. I can whack (that's a technical term) everything back into line on the trail after a good crash then. Things tend to not break either in my experience.

If there is one thing I am good at, it's tossing and or dropping dirt bikes!

Just my experience. Others may vary....

 

[louemc]

Definitely too vague for anyone in the business, but a worthy statement for the average joe who might think, "I want stronger bolts!" Without knowing there may be trade offs involved.

These days, the level of engineering and manufacturing quality afforded to your average, "over the counter" bolt also makes it a quality statement.

You're right... But we are talking apples to oranges here. The whole topic here is broken bolts. We are talking about bolts. Over the counter bolts as well.
Bringing in an example dealing with punch press tooling is like bringing in a linebacker as your pinch hitter.

There is no way in hell to detail/define the ingredients in the catalog of tool steels, and the heat treatment process's including the tempering for the added toughness, without losing needed hardness for the wear resistance.

The reader not knowing, because that isn't what they have been learning and working at... Isn't going to learn anything in a post.

And there is the little matter of rolling threads, instead of cutting them.
The rolling works the steel like forging it does (gives the molicules discipline).

And if cutting the threads was done ... How pointed was tip of the tool forming the root of the thread?
(Sharp points focus stress that start failures)

 

[DefyInertia]

You have,, to feel the steel, know which bolts to get and,, how tight,, they should be without thinking! Just joshin' pretty interesting topic.

I wacked my fare share back into place but never really gave over torquing too much thought outside of the usual negative consequences. Learned something.

 

[Charles R]

There is no way in hell to detail/define the ingredients in the catalog of tool steels, and the heat treatment process's including the tempering for the added toughness, without losing needed hardness for the wear resistance.

The reader not knowing, because that isn't what they have been learning and working at... Isn't going to learn anything in a post.

And there is the little matter of rolling threads, instead of cutting them.
The rolling works the steel like forging it does (gives the molicules discipline).

And if cutting the threads was done ... How pointed was tip of the tool forming the root of the thread?
(Sharp points focus stress that start failures)

Again. You are right.
Which is exactly why the statement, "The harder/stronger a metal is, the more susceptible it is to the growth of fatigue cracks" works in the context of this thread. The average/majority person is going to go down to the local hardware store for grade 8, over a grade 5, or grabbing that "ultra strong" generic titanium bolt at the moto parts shop, without any idea of how that bolt was processed. And these days, that really is a big unknown.

Plus, now you are talking about processes to prevent the formation of fatigue cracks, not growth after the crack has started. These important processes are done why?...because...wait for it... The harder the metal is, the more susceptible it is to the growth of fatigue cracks! Lol.

I know what you are trying to convey Lou, and it's a valid statement too. But my statement means "be cautious when trying to upgrade hardware". And I'm quite sure most people in this thread understand that.
Are you really trying to say, "just blindly trust the label, because they have done ALL the steps required to actually make that bolt stronger!"? I think you're smarter than that. I also think you're smart enough to know that 99% of the world will never do a full investigation into the background of the hardware they will buy.

So my statement stands, no matter how "flawed" it may seem to you.

 

[louemc]

Again. You are right.
Which is exactly why the statement, "The harder/stronger a metal is, the more susceptible it is to the growth of fatigue cracks" works in the context of this thread. The average/majority person is going to go down to the local hardware store for grade 8, over a grade 5, or grabbing that "ultra strong" generic titanium bolt at the moto parts shop, without any idea of how that bolt was processed. And these days, that really is a big unknown.

Plus, now you are talking about processes to prevent the formation of fatigue cracks, not growth after the crack has started. These important processes are done why?...because...wait for it... The harder the metal is, the more susceptible it is to the growth of fatigue cracks! Lol.

I know what you are trying to convey Lou, and it's a valid statement too. But my statement means "be cautious when trying to upgrade hardware". And I'm quite sure most people in this thread understand that.
Are you really trying to say, "just blindly trust the label, because they have done ALL the steps required to actually make that bolt stronger!"? I think you're smarter than that. I also think you're smart enough to know that 99% of the world will never do a full investigation into the background of the hardware they will buy.

So my statement stands, no matter how "flawed" it may seem to you.

What you said is flawed.. You're not understanding what I was saying.

Tool steel, name/grade/process of manufacture, preventing failure starts on Screws - Bolts, that are doing a designed job...
Aren't getting fatigue cracks to be growing cracks.


The engineers that chose the Bolt or Screw size, and grade, made the "investigation".
The 99% of the world, Doesn't have to.

I'm thinking that you are Not qualified to decide or determine what my smartness is, in this field.

 

[Charles R]

I understand what you are trying to say far more than your opinion of me implies. I'm not the one who has consistent communication issues with the general masses here on barf.

 

[somesuch]

I was worried about my handlebar bolts, so I went out last Saturday to test them...looks like the bolts were ok.

 

[gixxerjeff]

I was worried about my handlebar bolts, so I went out last Saturday to test them...looks like the bolts were ok.

Sad and funny at the same time.

 

[louemc]

Sad and funny at the same time.

Oh Man, now I'm going to rant about cast Aluminum...

 

[somesuch]

Oh Man, now I'm going to rant about cast Aluminum...

It is the Renthal bars in the picture, and considering the hit they took, I don't think anything else would have done better....The master cylinder is another story

Brembo brake lever bent 90° and did not break!

 

[somesuch]

Oh Man, now I'm going to rant about cast Aluminum...

It is the Renthal bars in the picture, and considering the hit they took, I don't think anything else would have done better....The master cylinder is another story

Brembo brake lever bent 90° and did not break!

 

[Entoptic]

As the folks on MV Agusta forum said to me when this happened. "Your situational awareness is poor." I lolled at them and told them to actually ride their bikes instead of stare at it.

Sorry to hear OP.