Bolt grades....

[jwilliams3]

I recently purchased an adjustable hitch.

It takes 2 bolts to mount it secure to its channel.



What bolts are good for this task?



Is it ok to use a High grade bolt for this? Or are Higher grades subject to shear easily?

 

[Hoefler]

I would contact the manufacturer for the recommended bolts. They know the specs it was built for. Most receivers are installed using grade 5 coarse thread bolts, will equalizing heads use grade 8 fine thread. The fine thread will hold their torque better than coarse thread and will take higher torque . Grade 8 bolts can fatigue and fracture in the wrong application, such as a joint that will flex, they are perfect for pinching attachments where friction does the majority of the work. , like bolting through a bar inside a channel. If this connection does not stay tight and is subject to work, grade 5 would be better suited, while it might distort a little, the grade 8 cannot take the pounding and will break. Hope this helps.

 

[RustyJC]

Many (most?) of the hitch manufacturers use Grade 5 fasteners for their ductility. If you think about it, the engineer can upgrade the Grade 5 fastener's size to get the equivalent tensile clamping force of a smaller, but adequate, Grade 8 fastener and benefit from the increased ductility and decreased notch and corrosion sensitivity of the Grade 5.



I've seen photos of RV 5th wheel hitches that have been involved in major collisions. In many of these, the fasteners have distorted to absorb the forces, but I've never seen one that's pulled apart or fractured.



Rusty

 

[jwilliams3]

Ok,

Looks like I am better off with a grade 5 because they will flex more correct?



Basically all I want these bolts to do is to retain the unit and not snap off.

There is not going to be over say 20ft lbs on the bolts them selves.



Its for a sledpulling application to keep a pintle eye in its channel.

 

[RKerner]

Many (most?) of the hitch manufacturers use Grade 5 fasteners for their ductility. If you think about it, the engineer can upgrade the Grade 5 fastener's size to get the equivalent tensile clamping force of a smaller, but adequate, Grade 8 fastener and benefit from the increased ductility and decreased notch and corrosion sensitivity of the Grade 5.

Also, the application of whether the bolt is in single shear or double shear comes into play for determining bolt grade/size and shank length. Putting the thread minor diameter into shear will work in most cases until loads start flexing the bolt. Grade 8 fasteners have applications and when applied properly, will work as planned. In the world of cost reduction, Grade 8's are not used until absolutely necessary. Most fasteners fail due to a relaxation of bolt tension/clamp load which then works on minor diameters which is the second weak spot of the bolt. The radius under the bolt head is the other primary weak area.

Ok,

Looks like I am better off with a grade 5 because they will flex more correct?



Basically all I want these bolts to do is to retain the unit and not snap off.

There is not going to be over say 20ft lbs on the bolts them selves.



Its for a sledpulling application to keep a pintle eye in its channel.

I'm looking at two adjustable hitches right and they use hitch pins for the ball to channel attachment. These pins transfer the load to the vertical portion of the hitch which then goes into the reciever, so they are load bearing. Maybe you could post a pic which would aid suggestions for which type of fastener to use.