A middle ground between the screw collar pin and the safety nut and bolt. The square head lets the pin be tightened with a spanner rather than by hand alone, so it can be set considerably firmer than a collar pin and is far less likely to work loose — while still being quicker to fit and remove than a bolt, nut and split pin assembly.
It suits connections that are semi-permanent: made for a job that lasts days rather than minutes, but broken down afterwards. Five sizes covering the most-used band of the range, 3.25 to 9.5 tonnes.
Key Features
- Square head pin: Tightened with a spanner, so it can be set firmer than a hand-tight collar pin and resists loosening better.
- Quicker than a safety pin assembly: No nut and split pin to fit, so it sits between the two in both security and speed.
- Bow body: Multi-leg slings and varying load directions.
- 6:1 minimum breaking load to BS EN 13889.
- Hot dipped galvanised.
- Five sizes: 3.25, 4.75, 6.5, 8.5 and 9.5 tonnes.
- Fully marked: CE, W.L.L., manufacturer's identification, size and traceability code.
Technical Specifications
| Product Code |
W.L.L. (t) |
A (mm) |
B (mm) |
C (mm) |
d (mm) |
Weight (kg) |
| BPSQB3.25 |
3.25 |
16 |
19.1 |
27 |
64 |
0.79 |
| BPSQB4.75 |
4.75 |
19 |
22 |
31 |
71 |
1.26 |
| BPSQB6.5 |
6.5 |
22.2 |
25 |
36 |
83 |
1.88 |
| BPSQB8.5 |
8.5 |
25.4 |
28 |
43 |
95 |
2.78 |
| BPSQB9.5 |
9.5 |
28.6 |
32 |
46 |
90 |
3.87 |
All dimensions in millimetres. Note dimension d reduces from 95 mm on the 8.5 t to 90 mm on the 9.5 t.
BS EN 13889 | MBL 6 x W.L.L. | Square Head Pin | LOLER Ready
Grade 6 high tensile steel body and pin, quenched and tempered, meeting the Working Load Limit requirements of BS EN 13889. Minimum breaking load is six times the W.L.L. Hot dipped galvanised. Marked with CE, W.L.L., manufacturer's identification, size and traceability code. Under LOLER 1998, thorough examination by a competent person at intervals not exceeding 12 months.
Suitable Applications
Square head shackles suit semi-permanent connections: rigging set up for a job lasting days or weeks then broken down, site installations, temporary works, and anywhere a connection needs to be more secure than hand-tight but will not be left indefinitely. They are also useful where a screw pin has previously worked loose and a full safety pin assembly is more than the situation requires.
More About This Product
Shackles are the most-handled component in any lifting operation, and that is precisely why they wear out first. A sling gets rigged and derigged; a shackle gets rigged, derigged, dropped, driven over, thrown into a box and picked up by whoever needs one. Most lifting gear fails from a single overload; shackles fail from accumulated inattention.
The grade markings matter more than most people realise. A Grade 6 high tensile shackle to BS EN 13889 and a Grade 8 alloy shackle look similar and share the same body shape, but the alloy version carries considerably more at the same size. Once a shackle is in a box with fifty others, the only way to tell them apart is the marking — which is why an unmarked shackle has to be scrapped no matter how good it looks.
Understanding the Load Path
A shackle has two distinct load-bearing elements and they do different jobs. The bow takes the sling; the pin takes the load. Reverse that — put the sling on the pin and the load on the bow — and two things happen. The sling bears on a smaller radius than it was designed for, and any movement in the sling starts to rotate the pin.
On a screw collar pin that rotation is the failure mechanism. A sling shifting under a settling load, or vibration transmitted from plant nearby, will slowly unscrew the pin over minutes or hours. It rarely happens quickly enough for anyone to see it happening.
The second consideration is angle. A shackle loaded in line with the pin carries its full rating. Loaded at an angle across the bow it carries substantially less, and published derating tables cover a limited range of angles — beyond that range no figure is published because none applies. On a multi-leg sling every leg is at an angle by definition, which is why the bow shackle exists and why putting a multi-leg sling into a dee shackle is a genuine mistake rather than a preference.
How to Use the Shackle
- Tighten with a spanner: That is the point of the square head. Firm but not overtightened; the pin should seat, not be forced.
- Load in line with the pin, not across it.
- Recheck tightness periodically: More secure than a collar pin, but not positively locked like a safety pin. On extended installations, check it.
- Watch included angle on multi-leg slings.
- Do not substitute the pin.
- Do not modify: Never weld, heat, machine, drill or repaint.
Warning: A square head pin is more secure than a screw collar but is not positively locked. For genuinely permanent installations or anything subject to sustained vibration, use the safety nut and bolt version.
Safety Information
- Never exceed the marked Working Load Limit.
- Tighten the pin fully with a spanner and recheck periodically.
- Load in line with the pin. Do not side load unless rated for it.
- Never substitute a bolt or non-original pin.
- Derate for included angle on multi-leg slings.
- Withdraw any shackle showing wear beyond the manufacturer’s stated limit, distortion, bow spreading, thread damage or cracks.
- Never weld, heat treat, machine or repaint.
- Thorough examination by a competent person required at intervals not exceeding 12 months under LOLER 1998.
Inspection and Maintenance
As with any shackle, measure the bow at its narrowest point against original dimensions and check for spreading. Inspect the pin thread and the tapped hole for damage, stripping and corrosion, and check the square head itself for rounding, since a rounded head cannot be properly tightened and the shackle loses its advantage over a collar pin. Look for wear at the crown and pin bearing points, withdraw at 10%, and confirm markings remain legible.
Downloads
Frequently Asked Questions
Q: Where does this sit between screw pin and safety pin?
In the middle, deliberately. Tightened with a spanner so it is far more secure than a hand-tight collar pin, but without the nut and split pin of the safety version. It suits semi-permanent rigging: more than a shift, less than forever.
Q: Can I use it for a permanent installation?
For genuinely permanent rigging or anything subject to sustained vibration, use the safety nut and bolt version. The square head resists loosening but is not positively locked, and permanent means nobody will be checking it.
Q: Why only five sizes?
3.25 to 9.5 tonnes covers the band where semi-permanent rigging is most common. Below that, connections tend to be temporary and a screw pin suffices; above it, they tend to be permanent and warrant a safety pin.
