Shackle working load limits
These are Grade 6 (Class 2) carbon steel anchor shackles at a 6 to 1 design factor, which is the common commercial grade. Alloy Grade 8 shackles carry more at the same size and are marked accordingly.
The size stamped on a shackle is the body diameter. The pin is always thicker, so measuring the pin will give you the wrong size.
| Size | Metric | WLL (t) | Pin dia |
|---|---|---|---|
| 3/16 in | 5 mm | 0.33 | 1/4 in |
| 1/4 in | 6 mm | 0.50 | 5/16 in |
| 5/16 in | 8 mm | 0.75 | 3/8 in |
| 3/8 in | 10 mm | 1.00 | 7/16 in |
| 7/16 in | 11 mm | 1.50 | 1/2 in |
| 1/2 in | 13 mm | 2.00 | 5/8 in |
| 5/8 in | 16 mm | 3.25 | 3/4 in |
| 3/4 in | 19 mm | 4.75 | 7/8 in |
| 7/8 in | 22 mm | 6.50 | 1 in |
| 1 in | 25 mm | 8.50 | 1 1/8 in |
| 1 1/4 in | 32 mm | 12.00 | 1 3/8 in |
| 1 1/2 in | 38 mm | 17.00 | 1 5/8 in |
Bow against dee shackles
A bow or anchor shackle has a rounded body and can take a load from more than one direction, which makes it the right choice when several sling legs collect at one point.
A dee or chain shackle has a narrow body and is meant for a straight in-line pull only. Loading one at an angle bends it, and a bent shackle is scrap.
Screw pin shackles are for temporary connections where someone checks them. If the shackle stays in place, or if the load can rotate and unscrew the pin, use a bolt type with a nut and split pin instead.
Side loading reduces capacity
The rated capacity assumes the load pulls in line with the shackle body. Pull it at an angle and the rating falls, because the bow is being bent rather than stretched.
Never side-load a dee shackle at all, and never load a shackle across the pin.
| Angle from in-line | Proportion of WLL |
|---|---|
| 0° (in line) | 100% |
| 45° | 70% |
| 90° (side load) | 50% |
What to inspect before use
Check the shackle carries a legible size and WLL marking and a manufacturer identification. An unmarked shackle is not rated lifting gear whatever it looks like.
Reject any shackle with a bent or stretched bow, a pin that does not seat fully, thread damage, nicks, gouges or corrosion pitting, or more than 10 percent wear at any point.
Never replace a shackle pin with a bolt. The pin is a matched, rated component and a bolt of the same diameter has a different shear strength and thread engagement.
