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In summary, the conversation discusses how to determine the pull out strength of a thread when attaching two parts with bolts. The suggested method involves calculating the shear area and multiplying it by the shear strength of the softer component in the bolted joint. It is also important to consider the strength of the materials being used and to include a safety factor in the calculation. Additional resources such as Engineer's edge and MIL-HDBK-60 are recommended for further information.
- #1
Spoolx
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Hi All,
I was browsing the internet and came across this forum, I was thinking to myself one day and decided to do a google search.
My question is basically, how do I determine how much weight a bolt can take before it pulls out of the thread.
For example, I want to attach Part A to Part B with bolts and I am trying to determine the proper size. I am sure there is a formula that will tell me how much weight a bolt can take based on what material it is threaded in to, but I can't seem to find it.
I have my machinists handbook out but am having no luck, a point in the right direction would be much appreciated. I also have an old physics book and even if you could point me to the section of the book that deals with this concept, that would be appreciated also.
Thanks
Rich
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- #2
Mech_Engineer
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Generally to determine pull out strength of a thread you will basically calculate the shear area (pi * shear diameter * length of engagement), and multiply by the shear strength of the softer component in the bolted joint.
You must decide which is the stronger material (or if they're both about the same)- the internal thread or external thread. If the internal thread (threaded hole) is stonger, your shear diameter should be about the minor diameter of the thread. If the external thread (bolt) is stronger, the shear diameter will be the major diameter of the thread. If both materials are about the same in terms of strength, use the pitch diameter of the thread.
This is a quick estimate, so make sure and build some safety factor in there as well. Generally as long as your length of engagement is >= 1.5x the nominal diameter of the thread, the fastener will snap before the threads pull out. However this is dependent on the materials being used.
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Q_Goest
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Engineer's edge has a decent write up including some calculators.
http://www.engineersedge.com/torque.htm
http://www.engineersedge.com/calculators/torque_calc.htm
http://www.engineersedge.com/fastener_thread_menu.shtml
- #4
Spoolx
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thanks a bunch guys
- #5
ty2nu
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MIL-HDBK-60 is good place to start.
Related to How much weight can a bolt take before the threads pull out?
1. What is the maximum weight a bolt can hold before the threads pull out?
The maximum weight a bolt can hold before the threads pull out depends on various factors such as the material and size of the bolt, the type of thread, and the surface it is attached to. It is important to consult the manufacturer's specifications for the specific bolt being used.
2. How do I determine the maximum weight a bolt can hold?
To determine the maximum weight a bolt can hold, you need to consider the shear strength and tensile strength of the bolt. Shear strength is the amount of force a bolt can handle before breaking, while tensile strength is the amount of force a bolt can handle before it starts to deform. The lower of the two values is the maximum weight the bolt can hold.
3. Can I increase the weight a bolt can hold by using a larger diameter bolt?
Yes, using a larger diameter bolt can increase the weight it can hold. This is because a larger diameter bolt has a larger cross-sectional area, which can distribute the weight more evenly and reduce the stress on the threads.
4. What happens if I exceed the maximum weight a bolt can hold?
If you exceed the maximum weight a bolt can hold, the threads may start to pull out, causing the bolt to fail. This can lead to structural damage and potential safety hazards. It is important to always use bolts that are rated for the weight and load they will be subjected to.
5. Are there any other factors that can affect the weight a bolt can hold?
Yes, other factors that can affect the weight a bolt can hold include the quality of the threads, the installation method, and the environmental conditions. It is important to ensure that the bolt is properly installed and maintained to ensure its maximum weight-holding capacity.
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