Where Hard-to-Reach Bolts Occur
In railway construction and maintenance, certain rail bolts present genuine accessibility problems: bolts beneath the rail foot, bolts inside the confined space of clip seats, and bolts in special track structures such as crossings and guard rail assemblies. The difficulty is not the torque value, which is usually modest, but the geometry. A standard socket wrench needs swing space, a straight extension bar needs clearance, and the operator needs a visible line of sight for thread alignment. When none of these exist, the job requires dedicated tooling and a method that keeps both the operator and the fastening safe.
Tooling for Restricted Access
| Access condition | Recommended tooling |
|---|---|
| Bolt below the rail foot, vertical clearance only | Low-profile socket with universal joint and extension bar |
| Bolt in a clip seat, obstructed by clip and shoulder | Bent-handle or offset socket wrench |
| High torque required in confined space | Hydraulic or electric torque wrench with offset or low-profile head |
| Heavy-haul and port crane track, many bolts | Compact impact wrench or pneumatic ratchet wrench |
| Insulated or explosion-proof zones | Insulated-handle tools or non-sparking alloy tools |
Long-handled and bent-handle socket wrenches and ratchet wrenches, combined with universal joints or extension bars, transmit torque from various angles while keeping the operator clear of the track. For high-strength bolts that need substantial torque, low-profile or offset hydraulic and electric torque wrenches apply the required preload without swinging space. Compact impact wrenches and pneumatic ratchet wrenches are particularly effective on heavy-haul railways and port crane tracks, where their short bodies and flexible angles allow high-speed tightening in restricted areas.
Working Around Obstructions Safely
When a bolt is partially obstructed by other components, the correct move is to remove the blocking element temporarily or, where the rail itself blocks access, to lift the track under controlled conditions. Both operations must follow the local safe working procedure, with the track possession or protection in place, and the removed elements must be reinstated and the fastening re-verified before traffic resumes. Under no circumstances should the operator attempt to bend the tool or force an incorrect angle, because the resulting side load damages both the thread and the tool.
Torque Control and Verification
Reaching the bolt is only half the job. Clean threads, uniform torque application and post-installation verification are equally critical: a bolt tightened through a universal joint at an angle loses effective preload compared with straight tightening, so the torque setting must be corrected for the joint efficiency, or the final preload verified with a calibrated torque wrench. Post-installation checks prevent localised loosening, which is what causes gauge deviation and fastener failure in service. Fish bolts, which join rails at every joint, are the most common hard-to-reach bolts on track, and their typical dimensions follow the rail section:
| Fish bolt type | Dimensions | Weight (kg) |
|---|---|---|
| HS26/55 | M22 x 55/40, nut M22, H22/S39 | 0.45 |
| HS26/65 | M22 x 65/45, nut M22, H22/S39 | 0.475 |
| HS26/90 | M22 x 90/45, nut M22, H22/S39 | 0.549 |
| HS32/55 | M22 x 55/40, nut M22, H22/S39 | 0.469 |
| HS32/65 | M22 x 65/45, nut M22, H22/S39 | 0.503 |
| HS32/90 | M22 x 90/45 | 0.577 |
Environment-Specific Requirements
In environments with insulation requirements, such as rail sections carrying track circuits, insulated-handle tools prevent electrical hazards during maintenance. In explosion-proof zones, such as certain tunnel and industrial sidings, non-sparking alloy tools prevent ignition risk. The tooling rule is simple: match the tool to the hazard class of the location before matching it to the bolt size.
Common Misconceptions
A universal joint does not transmit the full torque setting at an angle; the preload loss must be compensated or verified after tightening.
Removing an obstructing component is not optional when the tool cannot engage the bolt squarely; forcing the angle damages the thread and the tool.
Impact wrenches are not a substitute for torque control on safety-critical bolts; they are used for speed, and the final preload is still verified.
Insulated tools are not only for electricians; on track with signalling circuits they are the standard protection for maintenance crews.
FAQ
Q1: Which bolts on track are typically hard to reach?
Bolts beneath the rail foot, bolts inside clip seats, and bolts in special track structures such as crossings and guard rail assemblies. Fish bolts at rail joints are also difficult where the fishplate and ballast leave little working room.
Q2: What tools are used for confined-space bolt tightening?
Long-handled or bent-handle socket and ratchet wrenches with universal joints and extension bars, low-profile or offset hydraulic and electric torque wrenches, and compact impact or pneumatic ratchet wrenches for high-volume work.
Q3: How do you keep correct preload when tightening at an angle?
Compensate the torque setting for the joint efficiency of the angled drive, or verify the final preload with a calibrated torque wrench. Post-installation verification is mandatory on safety-critical fastenings.
Q4: Is it safe to remove blocking components to reach a bolt?
Yes, under controlled conditions: follow the safe working procedure, protect the track, remove only what is necessary, and reinstate and re-verify the fastening before traffic resumes.
Q5: What are typical fish bolt dimensions at rail joints?
Common types are HS26 and HS32 series bolts, M22 diameter with thread lengths of 55, 65 or 90 mm, weighing between 0.45 and 0.58 kg depending on the rail section they serve.
Q6: When are insulated or non-sparking tools required?
Insulated-handle tools are required where track circuits or other electrical hazards are present, and non-sparking alloy tools in explosion-proof zones such as tunnels and industrial sidings.