Fastener Strength

[xroad]

In SAE fasteners, there are "spokes" on the head indicating hardness? Shear strength? What is the proper terminology?

What about metric? What are the notations?

 

[Charles (in GA)]

Google is your friend.

http://www.zerofast.com/markings.htm

http://www.zerofast.com/markings3.htm

http://www.nutsandbolts.com/v1-bolt-grade-markings.html

Google "bolt head markings chart" and "metric bolt head markings chart"

Charles

 

[xroad]

The last chart .... the SAE bolts looks like they have a lot higher strengths & hardness than metric fasteners. If a design need something strong, they have to go with SAE?

 

[Art From De Leon]

Metric fasteners are rated by a numeric system instead of the markings on the head of the bolt.


http://www.roymech.co.uk/Useful_Tables/Screws/Strength.htm

 

[nw2571]

The last chart .... the SAE bolts looks like they have a lot higher strengths & hardness than metric fasteners. If a design need something strong, they have to go with SAE?

The links above don't include metric 12.9 grade bolts. These are what are used for critical fasteners in almost all engines these days.... head bolts, rods, mains, etc.

http://euler9.tripod.com/bolt-database/22.html
Scroll to the bottom for mechanical properties.

 

[xroad]

Thanks all for the education. I love this forum.

 

[Here2Learn]

nw2571, thanks for the link:

"USA has become a world-class debtor to the tune of trillions due to inefficient business practices, low educational level, slackerism, and inability to solve or understand even simple problems such as metric conversion."

 

[djjsr]

Just an FYI -

Beware of counterfeit fasteners. It's a serious problem that started around 20 or 25 years ago when "offshore" companies started copying virtually everything. What you think is a grade 8 bolt may only have the strength of a grade 2. The government had a serious problem when these things started failing in critical applications such as aircraft, vehicles and even nuclear submarines. Lots of regulations have been enforced but they're still out there.

If you're interested, Google 'DOE’s Suspect Bolt Headmark List'. I have this list handy in my workshop just in case. The most recent ones that I've found were some grade 5 clutchhead bolts that broke just by tightening them with a tool similar to a nutdriver.

Just beware. If you can buy it cheap, it may not be what you think.

 

[nw2571]

Just an FYI -

Beware of counterfeit fasteners. It's a serious problem that started around 20 or 25 years ago when "offshore" companies started copying virtually everything. What you think is a grade 8 bolt may only have the strength of a grade 2. The government had a serious problem when these things started failing in critical applications such as aircraft, vehicles and even nuclear submarines. Lots of regulations have been enforced but they're still out there.

If you're interested, Google 'DOE’s Suspect Bolt Headmark List'. I have this list handy in my workshop just in case. The most recent ones that I've found were some grade 5 clutchhead bolts that broke just by tightening them with a tool similar to a nutdriver.

Just beware. If you can buy it cheap, it may not be what you think.

ARP's for all things critical in your engine builds! Just like the parts you're bolting together, you've got to know where they came from and that they're of high quality.

 

[caper]

Did a training course on fasteners from the Barnes/Bowman group last week at work.Some interesting stuff was learned.They did some interesting demonstrations with a machine which showed the amount of torque applied to a bolt and how it reached a plateau and then started dropping because the bolt was stretching.Showed how nuts are a throw away item because every time you reused them the clamping force dropped.Interestingly if you flipped the nut over it worked like new again but this only worked as a one time thing.They don't recommend the use of lock washers because they are a high failure rate item and locking nuts can be reused up to 6 times as long as they're not the nylock type which if you back them off even a 1/8 of a turn are no longer a lock nut.They did an interesting demo with the machine to show that even the sweat from your hands getting on a bolt provides enough lubrication that you need to use the lubricated value on a torque chart.The only time you can use a dry torque value is if you take the bolt out of the box and clean it with an evaporating solvent(brakekleen) and let it dry without touching the threads before using it.Some interesting stuff learned that day.

 

[MadMark]

Some good books on this subject:

Nuts, Bolts, Fastners and Plumbing by Carroll Smith
Can be found in the transportation section of Barnes & Noble or Borders

Mechancial Engineering Design by Shigley and Mischke
Find a used copy only, they make the students buy the latest editions, so
old editions should be cheap. (not too much calculus in this book, so everyone can get something out of it)

Machinery's Handbook.
Again look for an old edition. Machinists usually own this one.

Be carefull when designing for shear loads (perpendicular to the bolt's axis)
For example, a plate with four bolts may be under 1200 psi in shear. you would think that four bolts rated 400 psi in shear could do the job, but due to tolerancing of the bolt holes, only one bolt could be loaded, while the others are in the middle of the holes. So one bolt would have to be strong enough to withstand more than 1200 psi in shear. (Add 20% factor of saftey)