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Questions regarding maximum yield stress for standard hardened steel dowel pins Question
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Posted by: john2003

03/01/2006, 18:24:59

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Hello everyone,

I would like to ask if anyone could please help me with the following situation.

I am using a standard hardened steel "pull out" dowel pin from www.mcmaster(DOT)com as a bearing shaft. I need to know the maximum load the dowel / shaft can support without taking a permanent set and/or becoming permanently deformed or bent. I need the shaft to always spring back to its original position after the load is removed.

I emailed Mcmaster, but they were not able to give the maximum Yield strength of the dowels.

Does hardening increase the maximum Yield stress? If so, is there a way to calculate or estimate how hardening affects the yield stress ? If I know the yield stress, then I can compare the maximum yield to the bending stress given by my beam design program, and I think this will tell me if the dowel can support the load without taking a set.

Here is what Mcmaster said about the dowels and material...

"Hardened Steel- Made from hardened steel such as C1541, or 4037 and 4140 alloy steel. Core Rockwell hardness is C47-C58 (surface hardness is RC 60). Shear strength is the amount of force that the side of a pin can withstand before breaking. Single shear strength is the amount of force applied against a fastener in one place causing the fastener to break into two pieces. Single shear strength is 130,000 psi. An internally threaded tapped hole in one end of these pins lets you pull them out with a removal screw or a threaded puller such as 92330A (see page 3083 ) and reuse them. All meet ASME B18.8.2. Length tolerance is .010"."

I would appreciate any advice or suggestions on how I can get a close estimate on this, and what would be a reasonable safety factor to apply. Nobody could get hurt if the device fails, but I just need it to be reliable. I have to consider several factors when choosing a shaft size, and everything fits in a tight space.

There are tradeoffs and space constraints when going to a bigger shaft, so I need to know how to estimate this in order to make the best compromise. It's desirable to use the smallest shaft diameter possible, that will support the load with a reasonable safety factor & not take a set.

Thanks for your help.
John







Modified by Administrator at Wed, Mar 01, 2006, 18:59:51


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Re: Questions regarding maximum yield stress for standard hardened steel dowel pins
Re: Questions regarding maximum yield stress for standard hardened steel dowel pins -- john2003 Post Reply Top of thread Forum
Posted by: Kelly_Bramble

03/01/2006, 19:12:13

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For starters, expecting McMaster to signup to any specification is not a reasonable expectation. If you have lives at stake, I would bound my DP selection to a source that has tracable parts. Nothing against McMaster...

I would bound my part selection to an ASTM, MS, NAS, or ? specification. With an appropriate spec. and tracability, your calculations will have teeth. From which ever specification you settle on, do your math and put in an approriate FS. For fatique, you will want 20 or more, static loading, 10 should be ok.
Don't forget to verify you mating material.







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Re: Re: Questions regarding maximum yield stress for standard hardened steel dowel pins Smile
Re: Re: Questions regarding maximum yield stress for standard hardened steel dowel pins -- Kelly_Bramble Post Reply Top of thread Forum
Posted by: gyoung27

10/10/2007, 11:34:08

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Shouldn't you be more interested in the MINIMUM YIELD STRESS?

I wouldn't bet on McMaster-Carr testing their population of dowel pins and only sending you the ones with the highest yield stress, and even if they were to do that, what are the odds that they're all going to have the maximum yield stress attainable in the material?

Perhaps it would be a good idea to take the lowest yield stress value of all the possible dowel pin materials they listed for you calculations... 'cause you don't know what they sent you!








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