Great deals on TJ parts on Amazon!

Looking for parts for your Jeep Wrangler TJ? Checkout the selection of TJ parts Amazon has to offer, many with 2-day Prime shipping!

Click the image below to browse TJ parts on Amazon.

Jeep Wrangler TJ Parts on Amazon

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.

Bolted joints and how they're designed

Mike_H

Off-Camber is scary
Supporting Member
Joined
Feb 28, 2017
Messages
8,872
Location
Grand Rapids, MI, United States

Obi-Wan

TJ Enthusiast
Supporting Member
Joined
Apr 6, 2022
Messages
124
Location
Tatooine, Outer Rim
I just got my MET degree last week. It's way to soon to start reading about shear force, yield, elongation, grain structure, thread desgin, material selection etc.

If you're the nerd type, google Shigley's Mechanical Engineering Design. This guy literally wrote the definitive book of mechanical engineering.

My brain needs a vacation o_O
 
Last edited:
  • Like
Reactions: JMT, BlueC and Irun
OP
Mike_H

Mike_H

Off-Camber is scary
Supporting Member
Joined
Feb 28, 2017
Messages
8,872
Location
Grand Rapids, MI, United States
I just got my MET degree last week. It's way to soon to start reading about shear force, yield, elongation, grain structure, thread desgin, material selection etc.

If you're the nerd type, google Shigley's Mechanical Engineering Design. This guy latterly wrote the definitive book of mechanical engineering.

My brain needs a vacation o_O
I have that book. I worked with an older gentleman in my younger years that had Shigley as a prof at U of M.

Congrats on the degree. With an MET degree, there is a good chance you'll perform a lot of the testing that is described in the article I posted
 
  • Like
Reactions: Obi-Wan

mrblaine

Crew Member
Supporting Member
Joined
Nov 20, 2015
Messages
22,959
Location
Quail Valley, CA
This is a very good article, written by an automotive engineer. I know I've seen these discussions before, specifically about suspension joints. Read it, understand it, read it again. It's fact... Not opinion.


Let's give @mrblaine a break...
I really enjoyed the section on how the hole size relative to fastener diameter plays a huge role in how to design a slip critical connection.
 

mrblaine

Crew Member
Supporting Member
Joined
Nov 20, 2015
Messages
22,959
Location
Quail Valley, CA
It amazing how many folks think a bolt is typically used for its shear strength and not clamping force.
To be fair, some come by it honestly since the aircraft industry tends to confuse folks with an entirely different set of standards than typically found in the automotive world. They build around the concept of the bolt coming into shear in the event of torque loss and being able to handle that load while in shear as a safety aspect we don't need. They also have grip range specific fasteners to keep the threaded section out of the load area for the same reason.
 
  • Like
Reactions: pc1p and B00mb00m

B00mb00m

The Church of Cutting Brakes of Atlas-Front Digs
Supporting Member
Ride of the Month Winner
Joined
Jul 26, 2019
Messages
3,158
Location
Washington
To be fair, some come by it honestly since the aircraft industry tends to confuse folks with an entirely different set of standards than typically found in the automotive world. They build around the concept of the bolt coming into shear in the event of torque loss and being able to handle that load while in shear as a safety aspect we don't need. They also have grip range specific fasteners to keep the threaded section out of the load area for the same reason.
True, upon every installation the mechanic is free to range up or down a grip to insure threads are not in bearing and min number of threads are engaging the locking feature..

Good article!
 
  • Like
Reactions: Mike_H

mrblaine

Crew Member
Supporting Member
Joined
Nov 20, 2015
Messages
22,959
Location
Quail Valley, CA
True, upon every installation the mechanic is free to range up or down a grip to insure threads are not in bearing and min number of threads are engaging the locking feature..

Good article!
About the same level of confusing as using overhead lifting standards for rigging as the go to standard for recoveries. They are not related, never will be.
 
  • Like
Reactions: pc1p

mrblaine

Crew Member
Supporting Member
Joined
Nov 20, 2015
Messages
22,959
Location
Quail Valley, CA
It amazing how many folks think a bolt is typically used for its shear strength and not clamping force.
I spent some time one day pondering how many shear connections there were on a TJ versus how many slip critical. If I came up with any shear versions, I don't recall them with a single exception. If you have the factory tow hitch, the hitch pin is and that's it.

My favorite connection on the TJ? The two pins with threaded ends that hold on the door surrounds. They are awesome. They put points on the ends to help guide them through the holes and line everything up. The problem is they can't have a sharp point like that in the cabin for impact safety in a crash so they shortened the pin to keep the point up inside the threads which decreased thread engagement down to about 1 full thread. Perfect.
 

srimes

TJ Enthusiast
Supporting Member
Joined
May 19, 2021
Messages
883
Location
Oregon
I spent some time one day pondering how many shear connections there were on a TJ versus how many slip critical. If I came up with any shear versions, I don't recall them with a single exception. If you have the factory tow hitch, the hitch pin is and that's it.

My favorite connection on the TJ? The two pins with threaded ends that hold on the door surrounds. They are awesome. They put points on the ends to help guide them through the holes and line everything up. The problem is they can't have a sharp point like that in the cabin for impact safety in a crash so they shortened the pin to keep the point up inside the threads which decreased thread engagement down to about 1 full thread. Perfect.

Hinge pins. Door, tailgate, hood.. Something being called a "pin" is a good hint. Quick disconnect sway bar links... that's all I got
 
OP
Mike_H

Mike_H

Off-Camber is scary
Supporting Member
Joined
Feb 28, 2017
Messages
8,872
Location
Grand Rapids, MI, United States
We really do need more discussion about the section in there on hole size relative to fastener diameter.
I don't know how many people are picking up on this...but I'm laughing to myself.

You're right though...a lot of the dumb fastener discussions I remember revolve around hole size for a specific diameter. I can think of a couple very specific situations where size would matter, but they are teetering dangerously close to the realm of silly implausibility (sort of like dump truck springs on a TJ).
 

sab

"Semper Discens"
Lifetime Supporting Member
Joined
Jun 12, 2021
Messages
468
Location
DITHOT
I don't know how many people are picking up on this...but I'm laughing to myself.

You're right though...a lot of the dumb fastener discussions I remember revolve around hole size for a specific diameter. I can think of a couple very specific situations where size would matter, but they are teetering dangerously close to the realm of silly implausibility (sort of like dump truck springs on a TJ).
I picked up on it.
 

B00mb00m

The Church of Cutting Brakes of Atlas-Front Digs
Supporting Member
Ride of the Month Winner
Joined
Jul 26, 2019
Messages
3,158
Location
Washington
I don't know how many people are picking up on this...but I'm laughing to myself.

You're right though...a lot of the dumb fastener discussions I remember revolve around hole size for a specific diameter. I can think of a couple very specific situations where size would matter, but they are teetering dangerously close to the realm of silly implausibility (sort of like dump truck springs on a TJ).
I pride myself in subtle sarcasm and I missed this one.

Ahh yes the venerable wallowed track bar hole discussion.
 
  • Like
Reactions: Mike_H

mrblaine

Crew Member
Supporting Member
Joined
Nov 20, 2015
Messages
22,959
Location
Quail Valley, CA
Hinge pins.
Hinge pin, but that is part of the hinge which is held onto the vehicle at both sides with slip critical connections.
Door where? The latch is held to the body with SCC just like the hinges.
tailgate,
Latch, strike pin, and hinge are again, SCC except for the hinge pins.
Hood latch to hood, hood hinges to hood, hood hinges to tub are all SCCs with the exception of the hinge pins.
Something being called a "pin" is a good hint. Quick disconnect sway bar links... that's all I got
You can have all the pins you like, until you fasten what they work with to whatever with fasteners to complete the function, all you have are pins.