Thread: High Tensile Bolt Specifications

This may help.

Bolt Depot - Bolt Grade Markings and Strength Chart

Andrew

When you calculate off that, don't forget that you'll be using the minor thread diameter and not the metric sizing.

I am not quite sure how that chart works - eg a 1.2" (approx cross section of 1 square inch) grade 9 bolt has a tensile strength of 150,000psi - so what does that mean in terms of actual strength - does this mean it could safetly hold something that weighs 150,000ibs or about 70 tons. So a bolt with a cross section of .5 square inch can only hold 35 tons. From this chart how do I work out shear strength?

Thanks for the link

Garry

Most of the bolts that you buy now come from China, and even though they are marked grade 5, are not actually high tensile. I have had a few failures when putting in new bolts. The only place to reliably buy bolts from is Caterpillar. Their bolts all meet the specification that they are meant to. Buying good materials and tools is becoming increasingly hard. Even Sidchrome is now made in China.
Aaron.

Originally Posted by garrycol

I am not quite sure how that chart works - eg a 1.2" (approx cross section of 1 square inch) grade 9 bolt has a tensile strength of 150,000psi - so what does that mean in terms of actual strength - does this mean it could safetly hold something that weighs 150,000ibs or about 70 tons. So a bolt with a cross section of .5 square inch can only hold 35 tons. From this chart how do I work out shear strength?

Thanks for the link

Garry

Tensile strength is NOT safe working load! Tensile strength is the load at which the bolt will break. Safe working load is much less, how much less depends on a lot of factors such as the environment and the levels of acceleration and vibration expected. (typically perhaps 20% of tensile strength).

John

Originally Posted by JDNSW

Tensile strength is NOT safe working load! Tensile strength is the load at which the bolt will break. Safe working load is much less, how much less depends on a lot of factors such as the environment and the levels of acceleration and vibration expected. (typically perhaps 20% of tensile strength).

John

Not quite - it is (AFAIK) the point at which the bolt will begin to plastically (permanently) deform. So in laymans terms, when the bolt will begin to stretch, but failure will occur shortly after.

For (single) shear, tensile strength x 2/3 (0.66) will give you an approximate value.

John (Bush65) is the expert on bolts and bolted joints though. Dig up some of his posts or send a PM if you want the best answer.

Are you using metric or imperial bolts? The grades and markings are quite different.

Typical metric markings
grade 8.8 means 800MPa ultimate tensile strength (breaking load) and 80% of that (640MPa) yeild (when it starts to bend or stretch).
Likewise grade 4.6 means 400MPa tensile strength and 240MPa yield. These are basically mild steel and as soft as they get.

The highest tensile metric bolts you'll find are cap screws (allen key head), these are readily available in up to 14.9 and 12.9 depending on the size.

Safe working limits depend entirely on the geometry of the joint you're using them in.

mpa ?