# How to calculate the failure point of a pin

• pete
In summary, the conversation discusses the calculation of the weight a pin can hold before failing in a device that suspends from a chain. It is suggested to experiment and test the pin and take into account factors such as size, fit, and materials used. The possibility of other failure modes besides shear is also mentioned. A link is provided with information on calculating shear strength and an example is given for a bolt in double shear. The conversation concludes with the idea of making a test pin to determine its capacity.
pete
Hi, I have a device I'm suspending from a chain and the chain attaches to the body with a pin. I'm curious how you would calculate how much weight a pin like that could take before failing. There is a block on the body and a bar on the end of the chain that slots into the block and the pin goes through both and out the other side so it would have to shear the pin in two, in three actually so it seems unlikely but I would like to learn how to work it out myself so I know for sure.
I tried googling it but I got so many different answers that I got a bit confused so I thought I'd come and ask here?

They can be modeled and calculated, but mostly, the manufacturer will test his bolt or pin and then publish the result. Here is an example:
https://www.portlandbolt.com/technical/faqs/bolt-shear-strength-considerations/

First, let me better described what I think you have. There is a vertical channel through the block where the bar is inserted. Then the bar is held in place with a pin that crosses horizontally through the block and the bar.

It is best to determine the shear failure load by experimentation. It will be dependent on the size, fit, and materials used for the block and the bar. Also, there are other failure modes besides shear. If the block is made of a softer material, it could deformed and allow the pin to pulled through.

I like a Google image search for your terms in question. Your mind is very good at picking out pictures of your problem of interest and the pictures may lead to your answer.

https://www.google.com/search?q=SHE...Bs0KHRstCQIQ_AUIECgB&biw=931&bih=570&dpr=1.38

Thanks for the response. Yes, that's it more or less. The block is just over 40mm wide with a 30mm diameter hole through it and the bar which is also 30mm diameter slides into the hole then a 6mm pin goes through the block passing through the center of the bar. The block and bar are aluminum and the pin stainless steel. The aluminum could deform and loosen up the connection but the block or bar would have to tear themselves apart to actually fail so I'm sure the pin would go first.

I was thinking the block being slightly softer may even help prevent sudden failure as it will be harder for it to behave like a guillotine on the pin.

The link you provided has some information on how to calculate it. I'll haven't had time to read it properly yet but will later.

I'm afraid I've never done much maths so I'm not too good a reading stuff like that. To be clear what it means is that the stress on the bolt is equivalent to the force divided by the area. The area of the pin being the radius squared times Pi. I suppose the only difference is that there is no possibility for the pin to bend so when it fails it shears in half, although not in my case with the aluminum. I'm guessing it will all just get twisted up. But really I want it to be well within its capacity so it does not deform.

Maybe the best thing is to just make one up and load it till it fails, then I'll know for sure.

These equations are very neat and make sense but I never understand what units I would put in there to end up with a useful number. Like how much weight can the pin carry.

## 1. What is the failure point of a pin?

The failure point of a pin is the maximum amount of force or stress that the pin can withstand before it breaks or fails.

## 2. How is the failure point of a pin calculated?

The failure point of a pin can be calculated by using the formula for stress = force/area. By determining the maximum force that can be applied to the pin and the cross-sectional area of the pin, the failure point can be calculated.

## 3. What factors can affect the failure point of a pin?

The material of the pin, its size and shape, and the environment in which it is being used can all affect the failure point of a pin. Other factors such as the type of force being applied and the presence of any defects or flaws in the pin can also impact its failure point.

## 4. Can the failure point of a pin be predicted accurately?

While there are mathematical models and simulations that can estimate the failure point of a pin, it is difficult to predict it with 100% accuracy. This is due to the many variables and factors that can affect the failure point, as well as the potential for unforeseen circumstances or external forces.

## 5. How can the failure point of a pin be increased?

The failure point of a pin can be increased by using a stronger material, increasing the size or thickness of the pin, or making design modifications to distribute the force more evenly. Proper maintenance and handling of the pin can also help to prevent any weakening or damage that could lead to failure.

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