Grade 8.8 or equivalent clevis pins 5

[galaxy212]

Hi All,

Is there a reason why clevis pins are not graded? I have a steel rope anchor point that I want to secure with a clevis pin but all of the ones I can find on line are stainless steel or free cutting steel with no where near the strength of graded fasteners??

Cheers

 

[MintJulep]

Probably in recognition of the reality that they may be replaced in the real world by crap bolts, a length of ready-rod, rebar or whatever else is on-hand.

 

[StoneCold]

Maybe you should be using a shackle and shackle pin? That would have a specific rating.

Regard
Stonecold

 

[dhengr]

Galaxy212:
A shackle and its pin are designed and tested as a complete/integral system/unit, with a specified factor of safety w.r.t. unit’s safe working load. I certainly would assume that the manuf’er. should be able to tell you what material their product is made of. I would think you can use any pin material you want, as long as you design the new system so your pin is not the failure mechanism. This redesign should also include the pin itself, the pin hole and pin plate (padeye) to assure compatibility of the entire lifting/force system. A new pin of greater strength, with a smaller dia., or some such, is not always an optimal solution. Particularly if it over stresses some other part of the force reacting system.

 

[berkshire]

Galaxy 212
Aircraft clevis pins are graded as follows: Made of alloy steel per specification MIL-P-5673 and cadmium plated per QQ-P-416A, Type lI, Class 3. Provided with drilled hole for cotter pin. Used with clevis forks and in secondary controls which are not subjected to continuous operation.
You might also look at an aircraft clevis bolt. Of course I have no idea what size you need, and these may be way too small.
B.E.

You are judged not by what you know, but by what you can do.

 

[tbuelna]

As berkshire noted, there are mil-spec clevis pins available that use high-strength materials:

http://www.everyspec.com/MS-Specs/MS3/MS35000-MS35999/download.php?spec=MS35810B.008840.pdf

http://www.everyspec.com/MS-Specs/MS2/MS20000-MS20999/download.php?spec=MS20392F.007616.PDF

Of course, these clevis pins won't cheap.

 

[OSIRIS7]

Please take in mind that a clevis pin has to be calculated on shear. Whereas, bolting materials are specifically made for tension stresses. These graded bolting materials are often strengthened bij cold deforming them. Put such a bolt under shear stress, and it probably will fail way before you reach the tensile strength that is given for that material.

 

[galaxy212]

Thanks for the responses. I think next time I will use a shackle and pin. The equipment has been manufactured for clevis pins and space is tight so I can't really change. The SF on the maximum shear force with SS for the diameter of pins I am using is more then adequate, our company standard is to go for grade 8.8 fasteners though. By von mises, graded bolts have a significantly higher shear strength than other than SS so there is logic in it. Its frustrating that I know have to worry about bolt clamping in a connection that was not intended to be clamped because there are no readily available graded clevis pins.

 

[berkshire]

Did you also look at Clevis bolts, I mentioned these in my first post. they are essentially a shoulder bolt with a shallow round head or thin hex head. They are available in Europe in 8.8 grade, see my link.
B.E.


You are judged not by what you know, but by what you can do.

 

[galaxy212]

Thanks Berkshire, interesting part but it would make locking limited to thread lock because of the short thread length, is it intended to go straight into a tapped hole, I'm not really seeing where this part would be used in machine design over of bolt ?

 

[berkshire]

galaxy212 (Mechanical)
The short thread length is because the nut involved is a shear nut.
These bolts are designed to be a direct replacement, for a clevis pin in a clevis fork, which is loaded in shear only.
They are also available with a drilled shank for use with a castellated nut for extra security .
B.E.


You are judged not by what you know, but by what you can do.

 

[tbuelna]

galaxy212-

One thing to be careful about if you are going to replace a clevis pin with a shear bolt is to make sure the shear bolt has the correct grip and thread length to ensure the threaded portion of the bolt is never loaded in shear. This is the reason shear bolts have short, fixed thread lengths. When selecting the grip length of a shear bolt, make sure the body fully extends thru both lugs, and then use as many washers as necessary to ensure the nut does not bottom out on the short bolt threads when tightened.

Good luck.
Terry