Why 12 point head bolts and not 6 point ?

[Cressida]

I usually purchase and use 6 point sockets to avoid rounding off standard bolt heads.

I may have to pull the head on an older Camry (5SFE) and notice it has 12 point head bolts from the factory. I think that means I need to use a 12 point socket.

My question relates to why would the engineers have selected 12 point head bolts instead of the normal 6 point standard bolt heads? Since access is not going to be a problem, I can't understand what would be the advantage in using 12 point bolt heads. Perhaps it is just to distinguish them enough so that people notice that they are not normal bolts - surely that can't be the reason - anyone know or have ideas?

Update, this may be one reason:

"The 12 point design permits this style fastener to be tightened down with a 12-point socket wrench, permitting higher torques to be applied compared to a standard hex drive socket head fasteners."

 

[bigt61]

Easier access in tight spots.

 

[demarpaint]

Originally Posted By: bigt61
Easier access in tight spots.


Yes. It also pays to have a set of each.

 

[Olas]

My head bolts need long reach 12 point spline bits. I like to think its to prevent amateurs from getting themselves in trouble

 

[Trav]

No difference other than ease of access in tight places e.g. they can buried in deep holes without increasing the holes diameter for drive tools, U joint flanges, axle shafts, etc. They are more aesthetically pleasing though and can make a project look well finished.

 

[Hokiefyd]

Originally Posted By: Cressida

Update, this may be one reason:

"The 12 point design permits this style fastener to be tightened down with a 12-point socket wrench, permitting higher torques to be applied compared to a standard hex drive socket head fasteners."


This is what I've always understood. 12-point fasteners and sockets have double the contact points as compared with 6-point systems. This allows for higher torque loads with less of an associated increased risk of rounding the head.

 

[Kestas]

I believe the 12-pt design allows for higher torque with less chance of rounding the head. There are probably other benefits like easier to fit on the socket, within 1/12 of a turn instead of 1/6 of a turn.

When I was involved with aircraft, 12-pt bolts were used liberally.

 

[Johnny2Bad]

Originally Posted By: Kestas
I believe the 12-pt design allows for higher torque with less chance of rounding the head. There are probably other benefits like easier to fit on the socket, within 1/12 of a turn instead of 1/6 of a turn.

When I was involved with aircraft, 12-pt bolts were used liberally.


Used in Aircraft because, all things being equal, the 12-point is lighter. Might sound silly to choose something for a gram or three difference, but with the number of fasteners on an aircraft, it adds up. After all, this is an industry where they strip the paint off before repainting, to save the weight of the original paint.

Passenger with extra luggage:
"How many pounds overweight can the plane be before it crashes?"
Flight Engineer:
"One."

 

[bdcardinal]

I have been acquiring parts to rebuild the 5.0 in my 1995 Mustang. I have a pretty much complete set of ARP fasteners for it and all are 12 point.

 

[CR94]

Originally Posted By: Trav
... they can buried in deep holes without increasing the holes diameter for drive tools ...
Good point!

 

[andyd]

It has to do with ease of assembly by the robots

 

[JetStar]

Originally Posted By: Kestas
I believe the 12-pt design allows for higher torque with less chance of rounding the head. There are probably other benefits like easier to fit on the socket, within 1/12 of a turn instead of 1/6 of a turn.

When I was involved with aircraft, 12-pt bolts were used liberally.


+1 easier to wrench in limited access and tool indexing ease, increased torque capability which allows smaller head OD relative the shank, easier to safety wire, plus they just plain look cool.

 

[spackard]

After rust takes its toll, a 6 point fastener and tool have a better chance of loosening than a 12 point fastener and tool. Fasteners covered in oil don't suffer from rust. That's my story and I'm sticking to it.

 

[A_Harman]

If it was up to me, all bolts would be designed with 12-point heads. 12-point heads have twice the number of corners that would have to be rounded off before you can't loosen them. They take up less space than hex heads. The head diameters are the same as Allen heads. I have solved a few notable bolted joint design problems over the years using Ferris head capscrews.

 

[zeng]

Whilst 6 point bolts may come in Grades 8(high strength), 5 and 2 (low strength) materials, 12 point bolts come in Grade 8 (or higher strength materials) only.

 

[Trav]

6pt comes in grades up to 12.9. The amount of clamping force is the same as a 12pt fastener of the same grade.

 

[zeng]

Not sure if aviation ultra high tensile strength (metric size) Grades 13.9 and 14.9 bolt materials comes in 6 points too ?

 

[Trav]

I know they make them but never seen one in 6 pt cap only allen head, I know they use 14.9 on heavy paper making roll end supports but never heard of 13.9.