@ShedHead - Drake - you asked me about the shear strength of a 5/8" grade 8 bolt in pounds when used as a hitch pin. Its a rabbit hole for sure. Much out there on the interweb.
We don't need an engineer here. The idea is to have a general bias towards using equipment for which engineers and technical people have assigned ratings, and then knowing that the loads we are putting on that equipment has a "safety factor". Current thought is to stay conservatively (and this is subjective and empirical figure that may change as knowledge changes) at a 2:1 safety factor in a horizontal pull. Overhead lifting may use a 5 or 6 to 1 safety factor. Climbers may use a 10:1 safety factor. Will you be fine with a off the shelf hitch pin? Probably, but the grade is unknown so at least make sure it is a reputable brand. But for a couple dollars at the hardware store, why not use a Grade 8 bolt?
Now onto shear strength:
"unlike tensile and yield strengths, there are no published shear strength values or requirements for
ASTM specifications." (Source:
https://www.portlandbolt.com/technical/faqs/bolt-shear-strength-considerations/)
In general to find shear strength you multiply the tensile strength per square inch by the tensile stress area and then by .6 for shear strength (because shear strength is typically 60% of tensile strength). (source:
https://www.portlandbolt.com/technical/faqs/calculating-shear-strength-of-grade-8-bolts/)
Conditions:
- here we are discussing a bolt inserted into the holes but not tightened enough to provide a clamping force. If the bolt is clamping the receiver and insert together, you get strength from the clamping friction though to some extent you reduce the bolt shear strength because it is in tension (think about cutting a lose vs. tight piece of string). When you tow, the hitch weight results in some clamping friction between the receiver and insert.
- here we are discussing a shoulder bolt inserted into the holes where the shoulders touch all bearing surfaces (i.e. the threads are outside the receiver.
- Here we are discussing double-shear. When you simply bolt one thing onto another, that is single shear.
The minimum tensile strength of a
grade 8 bolt is 150,000 psi. A 5/8 coarse thread (11 threads per inch) bolt has a has Tensile Stress Area of .226 sq in. (150,000 x .226) x .6 = 20,340 single shear strength (where it should fail). In "double shear" it should take
40,680 to fail this 5/8" coarse thread grade 8 bolt.
By comparison, the minimum tensile strength of a
grade 5 bolt is 120,000 psi. A 5/8 coarse thread (11 threads per inch) bolt has a has Tensile Stress Area of .226 sq in. (120,000 x .226) x .6 = 16,2720 single shear strength (where it should fail). In "double shear" it should take
32,544 to fail this 5/8" coarse thread grade 5 bolt.
This
www.pirate4x4.com/tech/billavista/NutsandBolts/Nuts&Bolts_signed.pdf was a fun read today. Had not seen it before. Credibility of author unknown.
This is a informative reference:
FastenalTechnicalReferenceGuide.pdf
This is a reference that uses lots of words but kinda says nothing:
Hitch Pin Weight Capacity and Sheer Strength