A self locking hook does what a safety catch cannot: it stays shut. The mechanism locks closed as soon as the load is applied and can only be released deliberately, with two hands, once the load is off. That makes it the correct choice for lifts where the hook is out of sight, where the load may swing or rotate, or where an accidental release would be serious. The clevis fitting connects directly to the chain end link, giving a shorter and lighter termination than an eye hook and coupling link. Grade 10 alloy steel to BS EN 1677-3, for chain sizes 6 mm through 32 mm.
Key Features
- Positive self locking action: The latch locks under load and cannot be pushed open the way a sprung safety catch can. Release requires a deliberate two handed operation with the load removed.
- Clevis fitting: Connects direct to the chain end link with a load pin, removing the coupling link from the assembly. Shorter, lighter and one fewer component to inspect.
- Grade 10 alloy steel: Meets the Working Load Limit performance requirements of BS EN 1677-3 plus 25% of loads.
- Substantial throat: Dimension B, the throat, runs from 32 mm on the 6 mm size to 150 mm on the 32 mm, so the hook takes large lifting eyes and shackle bows.
- Nine chain sizes: 6, 8, 10, 13, 16, 20, 22, 26 and 32 mm.
- Full traceability marking: Marked with material grade, manufacturer's identification, size, product ID mark and traceability code.
Technical Specifications
| Product Code |
Chain Dia (mm) |
A (mm) |
B (mm) |
E (mm) |
F (mm) |
L (mm) |
M (mm) |
N (mm) |
Ø (mm) |
R (mm) |
| G100CSLH6 |
6 |
8 |
32 |
28 |
31.5 |
131 |
73 |
15 |
7.6 |
96 |
| G100CSLH8 |
8 |
9.5 |
36 |
36 |
40 |
163 |
90 |
21.5 |
9.8 |
121 |
| G100CSLH10 |
10 |
12 |
46 |
45 |
46 |
194 |
108 |
26 |
13 |
144 |
| G100CSLH13 |
13 |
15 |
59 |
53.6 |
66 |
251 |
137 |
32.5 |
15.8 |
182 |
| G100CSLH16 |
16 |
18.5 |
70 |
61 |
75 |
303 |
168 |
38 |
19.5 |
220 |
| G100CSLH20 |
20 |
25 |
85 |
76.5 |
80 |
337 |
190 |
50 |
24 |
235 |
| G100CSLH22 |
22 |
25.5 |
98 |
76 |
104 |
386 |
202 |
52 |
28 |
271 |
| G100CSLH26 |
26 |
30 |
118 |
99 |
107 |
484 |
251 |
60 |
33.5 |
343 |
| G100CSLH32 |
32 |
35 |
150 |
135 |
142 |
601 |
329 |
75 |
40.7 |
423 |
All dimensions in millimetres. B is the throat opening. Working Load Limits by chain size are given on the Cobra Plus specification data. The 26 mm and 32 mm sizes are available to order.
BS EN 1677-3 | Grade 10 | Self Locking | LOLER Ready
Manufactured from Grade 10 alloy steel and meeting the Working Load Limit performance requirements of BS EN 1677-3 plus 25% of loads. BS EN 1677-3 is the standard specific to self locking hooks. Each hook is marked with material grade, manufacturer's identification, size, product ID mark and traceability code, and supplied with a certificate. Under LOLER 1998, lifting accessories require thorough examination by a competent person at intervals not exceeding 12 months, or 6 months where used to lift persons.
Suitable Applications
Self locking hooks earn their extra cost wherever the consequence of a load coming off the hook is serious. That covers blind lifts where the hook cannot be observed, loads that rotate or swing in transit, work over occupied areas or public spaces, lifting near people, long duration suspended loads, offshore and marine lifting, and anywhere a slack sling might otherwise let the load slip. The clevis fitting keeps the assembly short, which matters where headroom is limited. For routine ground level lifting where the hook is watched throughout, a sling hook with a safety catch is more economical and quicker to use.
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 Self Locking Hook
- Match to the chain size: Select by nominal chain diameter and fit the clevis pin fully into the chain end link.
- Check the locking action before use: Open and close the latch. It must lock positively and release only with the deliberate two handed action. A latch that opens with one hand or under light pressure has failed.
- Seat the load in the throat: Load bears in the throat, never on the tip. Confirm the latch has locked before taking the weight.
- Release only with the load off: The mechanism is designed not to release under load and forcing it will damage it.
- Keep the mechanism clean: Grit and paint in the latch mechanism are the usual causes of failure to lock. Clean and lightly oil.
- Do not modify: Never weld, heat, machine, drill or repaint. Paint in the mechanism will stop it locking.
Warning: Never use a self locking hook whose mechanism does not lock positively. Never attempt to release the latch under load. Never tip load. Never repaint, as paint entering the mechanism prevents it locking correctly.
Safety Information
- Confirm the locking mechanism engages positively before every lift.
- Use only with Grade 10 chain and components of the matching size.
- The load must bear in the throat, never on the tip.
- Do not release the mechanism while the hook is under load.
- Withdraw from service any hook whose latch does not lock, is seized, bent or missing.
- Withdraw any hook showing throat opening, distortion, cracks or wear beyond the manufacturer’s stated limit of original dimensions.
- Never weld, heat treat, machine or repaint.
- Do not use above +200 °C or below -20 °C.
- Thorough examination by a competent person required at intervals not exceeding 12 months under LOLER 1998.
Inspection and Maintenance
The locking mechanism is what distinguishes this hook and it is what needs attention. Test the locking action before every lift, not just at inspection, because a mechanism fouled with grit or paint can fail between examinations. Keep the latch and pivot clean and lightly oiled, and be particularly careful that the hook is never repainted in service, since paint in the mechanism is the single most common reason self locking hooks stop locking. Beyond the mechanism, inspect as any other hook: measure throat opening against the original dimension, check the tip and throat for gouges and wear, check the clevis pin for straightness and full engagement, and confirm the marking is legible. Withdraw anything worn beyond 10% of original dimensions.
Frequently Asked Questions
Q: Is a self locking hook worth the extra over a sling hook?
It depends entirely on the lift. If the hook is watched throughout and the load lands where you can see it, a sling hook with a safety catch does the job. If the hook is out of sight, the load rotates, or the lift passes over people or public areas, the self locking hook removes a failure mode that a sprung catch does not. Price the risk, not the hook.
Q: How does the locking mechanism actually work?
The latch is held closed by the geometry of the mechanism, and applying load holds it more firmly shut rather than pushing it open. Releasing requires a deliberate two handed operation which cannot be done accidentally and cannot be done while the hook is loaded.
Q: Why does repainting matter so much?
Paint entering the latch pivot and mechanism can stop it locking fully while still looking closed, which is the worst possible failure because it is invisible. It also conceals cracks and wear. If the blue finish has worn, that is cosmetic. Do not repaint a lifting component.
Q: Clevis or eye fitting?
Clevis connects directly to the chain end link with a pin, which is shorter, lighter and has one fewer component. Eye connects via a coupling link, which adds length but makes the hook easier to swap. If headroom is tight, choose clevis.
Q: What does BS EN 1677-3 cover?
It is the part of the EN 1677 series specific to self locking hooks, setting out the performance and safety requirements for the locking mechanism as well as the hook itself. A hook marked to 1677-3 has been assessed against those locking requirements, not just general hook strength.
