A wire rope eye without a thimble is an eye that is slowly destroying itself. The rope bends round whatever it is connected to — a shackle pin, a hook — and that connection is harder than the rope. Under load the rope is crushed against it, the wires deform, and the eye fails long before the rest of the rope has done any real work.
A thimble is a grooved steel liner that sits inside the eye. The rope runs in the groove at a controlled radius, and the shackle bears on the thimble rather than on the wire. It costs 44p and it roughly doubles the working life of the eye.
**This is the lifting grade thimble.** It meets BS EN 13411-1, which the commercial thimble (TC) does not — that one is explicitly not for lifting. Check which you are buying.
Key Features
- Meets BS EN 13411-1: The standard for thimbles in lifting applications, plus the withdrawn BS 464. This is the one to use on a lifting sling.
- Controlled bend radius: Holds the rope at a radius it can tolerate rather than letting it bend tightly around a pin.
- Takes the bearing load: The shackle or hook bears on steel, not on wire rope.
- Hot dipped galvanised: Full corrosion protection, better than the electro galvanising on the commercial range.
- 15 sizes: 1/4" to 2", covering the full wire rope range.
- Very inexpensive: From 44p. There is no economic case for omitting one.
Technical Specifications
| Product Code |
Rope Dia (inch) |
A (mm) |
B (mm) |
L (mm) |
C (mm) |
S (mm) |
Weight (kgs/100) |
| TBS6 |
1/4 |
7 |
45 |
26 |
18 |
4 |
4.1 |
| TBS8 |
5/16 |
8 |
54 |
33 |
22 |
4 |
6.5 |
| TBS10 |
3/8 |
10 |
64 |
38 |
25 |
4.8 |
9.5 |
| TBS12 |
1/2 |
14 |
80 |
44 |
32 |
5.6 |
13 |
| TBS16 |
5/8 |
16 |
98 |
59 |
41 |
7.9 |
30 |
| TBS19 |
3/4 |
21 |
124 |
73 |
51 |
9.5 |
51.5 |
| TBS22 |
7/8 |
22 |
133 |
83 |
57 |
9.5 |
69.0 |
| TBS25 |
1 |
27 |
162 |
108 |
70 |
10.3 |
99.5 |
| TBS28 |
1 1/8 |
29 |
178 |
111 |
76 |
12.7 |
129 |
| TBS32 |
1 1/4 |
33 |
197 |
133 |
95 |
12.7 |
145 |
| TBS35 |
1 3/8 |
38 |
229 |
152 |
105 |
15.9 |
238 |
| TBS38 |
1 1/2 |
41 |
254 |
165 |
114 |
17.5 |
340 |
| TBS41 |
1 5/8 |
43 |
254 |
165 |
114 |
17.5 |
499 |
| TBS44 |
1 3/4 |
51 |
286 |
178 |
127 |
25.4 |
532 |
| TBS50 |
2 |
64 |
330 |
203 |
140 |
28.6 |
695 |
The heavy duty US style equivalent is the TUS range, meeting BS EN 13411-1 and US Fed. Spec. FF-T 276-b type 3, in 17 sizes from £0.41 to £113.31.
BS EN 13411-1 | Suitable for Lifting | Hot Dipped Galvanised
Mild steel, hot dipped galvanised, meeting the performance requirements of BS EN 13411-1 and the withdrawn standard BS 464. Suitable for use in lifting applications with wire ropes. Note the TC commercial thimble range is not for lifting use.
Suitable Applications
Fitted in the eye of any wire rope termination that will be connected to a shackle, hook or pin: wire rope slings, guy wires and stays, winch ropes, standing rigging, and any assembly where the eye takes repeated connection and disconnection. On a wire rope sling the thimble is effectively standard, and an eye made without one should be questioned.
More About This Product
Wire rope terminations are where most of a wire rope assembly's cost and nearly all of its risk sits. The rope itself is a commodity; the termination is where craft is involved and where efficiency is either preserved or thrown away.
The numbers are worth knowing. A properly made swaged or spelter termination retains close to the rope's full breaking load. A correctly fitted wedge socket retains a high proportion. A gripped termination with the right number of grips, correctly spaced and torqued, retains rather less — and a gripped termination done carelessly retains very little indeed. The rope has not changed; the termination has.
Termination Efficiency and the Thimble's Job
Efficiency is the proportion of the rope's breaking load a termination preserves, and it varies more than most people expect. That is why a lifting sling is swaged in a workshop and a guy wire is gripped in the field — the applications tolerate different efficiencies.
On a gripped termination three things determine the result and all three are commonly got wrong. The number of grips rises with rope diameter and is specified, not estimated. The spacing is specified by the manufacturer and set out in the instruction sheet. The torque must be applied and then reapplied after the assembly has been loaded once, because wire rope beds down under first load and grips that were tight become loose. A gripped termination inspected a week after fitting and never retorqued is a common finding.
And the orientation: saddle on the live rope, U-bolt on the dead tail. Reversed, the U-bolt crushes the part of the rope carrying the load. The rigger's phrase is never saddle a dead horse, and it exists because the mistake is easy to make and hard to see afterwards.
The thimble does a different job. Without one, a rope eye bends around the pin at a radius far tighter than the rope tolerates, and is crushed between pin and load. The thimble holds the eye at an acceptable radius and takes the bearing itself. A flattened thimble at inspection means the eye has been carrying load it was never meant to.
How to Use the Thimble
- Match the thimble to the rope size: An oversized thimble sits loose and can fall out; an undersized one will not seat.
- Seat the rope fully in the groove: All the way round, with no gap between rope and thimble at the crown.
- Secure the eye correctly: Ferrule, splice or the correct number of rope grips. The thimble protects the eye but does not form it.
- Check the thimble stays seated: A thimble that has worked loose in the eye is doing nothing.
- Use the lifting grade for lifting: TBS or TUS, not the TC commercial range.
- Replace rather than reuse a distorted thimble.
Warning: The TC commercial thimble range is not for lifting applications. For any lifting use, specify the TBS or TUS lifting grade. The two look similar and the difference is not visible on the product.
Safety Information
- Use only lifting grade thimbles (TBS or TUS) in lifting applications.
- Match the thimble size to the rope.
- The rope must seat fully in the groove all the way round.
- The thimble protects the eye; the ferrule, splice or grips form it.
- Withdraw any thimble that is distorted, cracked or has worked loose.
- Inspect the thimble and the rope eye together, since they wear as a pair.
- Where used in a lifting assembly, thorough examination by a competent person at intervals not exceeding 12 months under LOLER 1998.
Inspection and Maintenance
Check the thimble is still fully seated in the eye and has not worked loose or rotated. Inspect it for distortion, particularly flattening at the crown where the shackle bears, and for cracking at the point of maximum curvature. Look at the rope where it sits in the groove: if the thimble has deformed, the rope has been taking load it should not have. Check the galvanising for breakdown on assemblies used outdoors. A distorted thimble is a few pence to replace and is telling you something about the loads the eye has seen.
Downloads
Frequently Asked Questions
Q: Do I really need a thimble?
On any wire rope eye that connects to a shackle, hook or pin, yes. Without one the rope bends tightly around the pin and is crushed under load, and the eye fails long before the rest of the rope. At 44p it roughly doubles the eye's life.
Q: What is the difference between the BS and commercial thimbles?
The BS style (TBS) meets BS EN 13411-1 and is suitable for lifting. The commercial thimble (TC) is explicitly not for lifting applications — it is for fibre rope and general non-lifting work. They look similar and the difference is not visible, so check the code.
Q: BS style or US style?
Both meet BS EN 13411-1. The US style (TUS) additionally meets US Fed. Spec. FF-T 276-b type 3 and is a heavier section, which suits harder service. If you need US specification compliance, or a more robust thimble, choose TUS.
Q: The thimble has flattened. Does it matter?
Yes, on two counts. The thimble is no longer protecting the rope at the correct radius, and its deformation tells you the eye has been loaded harder than it should have been. Replace the thimble and inspect the rope eye carefully.
