×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

how to calculate a shear pin

how to calculate a shear pin

how to calculate a shear pin

(OP)
Hi,

I want to install a shear pin as a security device.
I think i do not use the proper way to calculate....
I've got a 3/4 shaft with 100 lbs-in of torque.
I need a shear pin made of bronze (shear constraint 6.5x10^6 psi).
I've found a pin dia of 0.005". something wrong i guess?!?
Can you help me.
Thanks

RE: how to calculate a shear pin

You appear to be using a stiffness modulus instead of the ultimate shear strength of the pin.  The strength is undoubtedly less than 100,000 psi.  Find Fsu, the ultimate shear strength, or find the ultimate tensile strength and estimate the shear strength as about 60 percent of the ultimate tensile strength.  Use this value in place of the 6,500,000 psi.

RE: how to calculate a shear pin

(OP)
thanks lcubed,
Make more sens with a 0.069 dia pin....
I thought that the shear modulus was the appropriate value.
(machinery's hanbook 26th edition page 384)
I use 60 000 psi (ultimate tensile strength)

RE: how to calculate a shear pin

I calculate your stress to be 35660 psi, which is about .6 x 60000, so that looks like a reasonable diameter to use.  Be aware that there is always some variation in strength of materials, and you may need to use a safety factor, or do some testing, depending upon the criticality of your application.  
Also, you said you had 100 in lb of torque, and we are discussing a pin which should shear at about that load.   If you want to carry that load, but shear at some higher value to prevent damage, you will need a larger pin.

Glad I could be of help.

Regards,
Lcubed

RE: how to calculate a shear pin

Mechanics of Materials, Beer & Johnson, Appdx B list:
Phosphor Bronze cold rolled shear 40 ksi


D=0.092" or 3/32"

RE: how to calculate a shear pin

You will need to 'neck' the pin to ensure it shears (fails)where you want it to.  Also it is best to house it in hardened bushes either side of the neck, if the aim is to simply replace it if it breaks.

 This method was widely used to protect overhead push-chain conveyors, some 20-30yrs ago before the advent of 'tripping' clutches

RE: how to calculate a shear pin

nzoldun,
I agree with your hardened bushing suggestion but I would differ with the "necking down" logic. The face to face contact zone will pretty well define the shear plane of the pin. I think the real reason some pins are necked down is to custom tailor or fine tune the shear area.

We make hay balers and the things still use shear bolts, some of which shear on an all too frequent basis depending on the operator!

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources