A replacement torsion spring fits the shaft, but the latch returns the wrong way. Another spring moves freely at the start and drags near the end of travel. Before changing the wire size or material, check whether the drawing and assembly instructions describe the same winding direction, viewing direction and angular positions.
For a buyer, “right-hand spring” and “clockwise movement” are not enough to approve a replacement. One describes the helix; the other describes motion from a particular viewpoint. The useful specification connects both to the fixed leg, moving leg and required load positions. This guide focuses on ordinary helical torsion springs; double torsion assemblies need their own load and mounting review.
Start with Dingli's spring product range, then check the assembly rather than selecting by appearance alone. The goal is a part that provides the required return action throughout the specified travel.
Specify the view before describing clockwise motion
A shaft rotation described as clockwise from one end appears counterclockwise from the other. An instruction without a viewing reference can therefore be interpreted differently by the designer, supplier and assembly team.
Put a viewing arrow on the drawing, identify the fixed leg and moving leg, and show the loading arrow separately from the desired return action. Use distinct labels for the shaft view and spring legs. Include the winding hand in text and show enough coil geometry for the supplier to confirm it.
Ask a practical question during review: can someone who has never seen the mechanism identify which leg moves, from which starting position, and in which direction? If not, the instruction still relies on local knowledge. A photograph helps with leg shape, but perspective and hidden coils can make it inadequate for confirming hand.
The real product photo illustrates leg geometry. It does not establish winding hand or a rated operating angle.
Match the winding hand to the loading action
The usual design approach for a helical torsion spring is to load it in the direction that winds the coil tighter. This direction principle is stated in Lee Spring's torsion spring guidance.
“Loading” means moving from the unloaded condition toward the specified operating condition. It should not be confused with the mechanism returning after release. Also avoid assuming that bringing the visible leg tips closer together always identifies the correct loading direction: bent or offset legs and different angle conventions can make that shortcut misleading.
Review the actual coil and mounting geometry with the supplier. If the mechanism must load in the opposite direction or travel across the free position, describe that requirement explicitly so the design and validation can address it. Do not force an unidentified sample backwards to test a guess.
A mirrored assembly also deserves a separate check. Turning a part over does not change its helical hand. Whether it can serve the opposite mounting position depends on leg bends, restraints, contact points and loading action.
Separate free leg position, preload and working travel
A free leg angle is a shape description. Angular deflection describes movement from a defined reference. These are related quantities, but a spring with a 90° free leg position is not automatically rated for another 90° of travel.
Use a state table to keep the purchase specification and inspection fixture consistent. The symbols below are a communication convention, not a mandatory drawing standard.
| Item | What to define | Common confusion |
|---|---|---|
| Free leg position | Unloaded leg geometry, angle convention and reference view | Treating a shape angle as allowable travel |
| Preload deflection θp | Deflection from free state to the installed start, with direction | Omitting preload from the final deflection |
| Working travel θw | Movement from installed start to end position, with direction | Giving mechanism travel without its starting state |
| Total deflection θtotal | For loading in the same direction, θtotal = θp + θw | Adding angles when the mechanism instead unloads |
| Torque inspection positions | Specified fixed and moving leg positions, with torque requirements | Stating an angle without its reference |
For illustration only, 20° of preload followed by 30° of travel in the same loading direction gives 50° of total deflection from free state. This arithmetic does not establish an allowable angle, torque rating or service life for a particular spring.
If travel unloads the spring or crosses its free position, record signed angular positions instead of applying that sum blindly. For acceptance, show the installed start and end positions directly on the drawing and specify the torque range and measurement conditions at each.
Check shaft and housing clearance at the loaded end
As the coil winds tighter, its inside diameter decreases; a close-wound body can also lengthen. These geometric changes are covered in Lee Spring's design considerations. Passing a free-state shaft fit check therefore does not prove clearance throughout travel.
Review the minimum inside diameter at the maximum working deflection against the shaft dimensions and tolerances. Include alignment and the finished mating surfaces. A mandrel percentage recommended for one catalog series should not be copied into every custom design.
Check axial space around washers, retaining rings and shoulders as well as the moving leg's swept area. A spring can feel excessively stiff when the added resistance actually comes from a rubbing leg or a constrained body. Record where contact occurs before changing the spring geometry.
Dingli's spring winding process and surface treatment information are useful starting points for discussing manufacturing and fit conditions. Any geometry change should be followed by a new torque and assembly review.
Compare torque at a defined contact point
A leg-tip force is not the same quantity as spring torque. For a force acting in the plane perpendicular to the spring axis, the moment about that axis is:
M = F × r⊥
M is torque, F is force, and r⊥ is the perpendicular distance from the axis to the force's line of action. Using N and mm gives N·mm. The full leg length is not automatically the effective moment arm; contact location and force direction determine the relationship.
If two samples feel different by hand, first compare them at the same leg position, contact point and force direction. Where the contact moves during travel, the effective moment arm may also change. An operating-force requirement should identify the measurement location and direction.
State angular rate units explicitly. N·mm/° and N·mm/rad cannot use the same numerical value interchangeably. Within an agreed approximately linear operating range, ΔM = kθ × Δθ describes a torque increment. It does not replace acceptance measurements at specified positions or establish fatigue life.
Contact points and force directions must be specified separately; they cannot be measured from this product photograph.
Make sample approval an assembly check
Approve the relationship between part and mechanism, as well as the free dimensions. Use the specified shaft, supports and contact features. The following sequence helps distinguish an incorrect hand from a reference-angle mistake or interference.
- Before installation, verify hand, leg geometry and free position against the correct drawing revision.
- At the installed start, record preload direction, contact points and starting torque.
- At an intermediate position, observe return action and any change in contact or friction.
- At the end, check total deflection, shaft clearance, axial space and the required torque.
- After unloading, record the returned position and investigate unexpected changes under the agreed conditions.
Use a guarded, controlled fixture for initial movement checks. A few slow movements can reveal fit problems, but they do not demonstrate cycle life. A life requirement needs a separate test plan defining the loading range, frequency, environment and failure criteria.
Keep observations tied to the same view. A short assembly sequence or marked photographs can explain a rubbing point more clearly than “too strong” or “does not return.” Include shaft dimensions and the torque positions when asking the supplier to investigate.
Turn the drawing review into a clear next step
A useful torsion spring specification connects winding hand, loading action, angular positions and mounting clearances. Together, these details explain the intended behavior and make a replacement easier to assess before production.
Cixi Dili Spring Co., Ltd., founded in 1995, works with customer drawings or samples for torsion and other custom spring requirements. For an assembly with reversed return action, end-of-travel binding or changed operating force, send the mounting sketch, sample images and inspection requirements through custom spring support. Material, torque limits, operating angles and validation should be agreed for the application.
Contact jackchen@dinglispring.com or WhatsApp +86 13586942004 to discuss the assembly requirements.
Frequently asked questions
Does a left-hand spring always mean clockwise operation?
No. Clockwise depends on the viewing direction and on which leg moves. Specify hand, reference view, fixed leg and loading arrow together instead of using a viewpoint-free shortcut.
Can turning a right-hand spring over replace a left-hand part?
Turning it over does not change its helical hand. Review leg bends, restraints, contact positions and loading action before deciding whether it can meet the opposite assembly requirement.
Does a 90° free leg position permit 90° of working travel?
No. Free position describes unloaded geometry. Permissible deflection depends on the spring design and operating conditions, and must be confirmed separately with the torque and acceptance requirements.
Why does binding appear only near the end of travel?
The loaded coil can have a smaller inside diameter, while axial space or leg clearance may become limiting. Inspect the actual end position rather than relying only on the free-state inside diameter.
Can a supplier work from a sample without a complete drawing?
A sample can start the discussion. Also provide the viewing reference, fixed and moving legs, start and end positions, shaft dimensions and target torque. Agree the resulting drawing and acceptance conditions before approving production.
