Which Shackle? So you know the working load limit… Are you done?

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BOW SHACKLE

In the last post we introduced some background on shackles and federal standards for shackles.  https://www.mantusmarine.com/wp-content/uploads/2013/11/shackle-document.pdf

In this post we will explore the subject of working load vs breaking strength in stainless steel shackles…   Many, when sizing gear look for one number “THE WORKING LOAD”  because once the working loads match up with, say, that of chain, all is dandy – right?  Maybe not so easy after-all,  here are a few examples that exemplify how confusing the subject could be:

Hayn  Hi- Mod Shackle

Pin size 0.5 inch
Material 316 Stainless Steel  (Process undetermined)
Working load limit not specified
Breaking load 13,200 lbs
Safety Factor not available
Price: $48.99 (defender.com)

Wichard Anchor / Bow Shackle 15/32

Pin Diameter: 15/32″ (0.47) inch
Material Forged Stainless Steel
Working Load: 4,576 lbs
Breaking Load: 13,200 lbs  
Safety factor 2.88  (If you look at Wichard Catalog this ratio between the working load and breaking strength is anywhere between 1.7 on some items and 4 on some others, no specification documents were referenced)
Price: $50.99 (defender.com)

Suncor Anchor /Bow Shackle  1/2 – ( a reference is made to ASME B30.26-2004) One should read this document there are almost no requirements on the manufacturer. Except it does suggest the working load should be 1/5 or 20% of the breaking strength. The same as recommended by the Federal Spec RR-C-271E 12 DEC 2010.

Pin Diameter: 0.51″
Material  315 Stainless Steel (Process undetermined Cast/Forged)
Working Load: 2,500 lbs
Breaking Load: 12,500  lbs
Safety Factor 5
Price: $22.99 (defender.com)

US Rigging 1/2 inch shackle

Pin Diameter 0.51″
Material 316 Stainless (Process undetermined Cast/Forged)
Working load: 2730 lbs
Breaking load 13,650 lbs
Safety Factor 5
Price: $12 (defender.com)

All these shackles have very similar dimensions and identical base material, and appropriately have similar breaking strengths, yet the working load of the Wichard Shackle is almost double that of others. This is where the customer might get confused and think that this shackle is twice as strong… Both the  RR-C-271E 12 DEC 2010 and the ASME B30.26-2004 call for the safety factor in shackles to be 5  i.e. working load limit needs to be 20% of the breaking strength. Since manufacturers do not always use working load in this way its worth while to be aware of this fact when outfitting your boat…..  cheers, and stay safe out there….