Machine Bolts vs. Grade A307

[300redbeard]

I know machine bolts come in various grades. On construction documents should 'machine bolts' call outs be referenced to comply with ASTM A307?

 

[Lutfi]

The answer is yes and no. It all depends what you are intending to use the bolds. If you have machined hinges or elements to be bolted to machine type tolerances, I would use the machine grades (i.e. grade 5 of 8). However, for structural steel applications, I would stick with ASTM grades.

Going from memory, while the grades might be close or equal between the two, there are dimensional differences (for example, the hex heads are not exactly the same).

Please correct me if I am wrong.


Regards,
Lutfi

 

[BAretired]

If using A-307 bolts, nuts should be snug-tightened and prevented from working loose using locknuts or lock washers.

BA

 

[Splitrings]

A307 is typically a structural bolt used in wood projects. Most "machine bolts" I would guess would meet SAE bolt standards; Grade #1, #2, #5, #8.

 

[Billybaru]

Note in the fastener distributor lingo, machine bolts typically refer to ASTM A307 Grade A Hex Bolts. These bolts have a min tensile of 60,000 psi, about half the strength as a grade 5 cap screw.

 

[JStephen]

I think there are testing differences or QC issues between the various specifiations, so it's not just a matter of comparing ultimate strength or yield strength.

 

[300redbeard]

Thank you all for your help.