Winding a mainspring outside the movement requires strict control, proper tools, and safe technique. This guide demonstrates how to wind a strike-side mainspring using a homemade winding block, cable ties, and a let-down tool. This method is ideal when a dedicated mainspring winder is not available and provides a safe, controlled way to compress the spring for reinstallation.
For related restoration steps, you may also find value in guides such as the Vienna Regulator restoration or the Ingraham 8-Day movement repair.
Tools and materials needed
Mainspring winding block
A wooden block with a central post and two safety-pin holes. This provides a stable platform for winding and prevents the spring from escaping.
Let-down tool
Used instead of a winding key. A let-down tool provides a full-hand grip, preventing injury if the arbor slips.
Leather gloves
Essential for protecting your hands from sharp edges and sudden spring movement.
Cable ties
Two cable ties linked together are used to contain the spring once it is compressed.
Safety nails or pins
Inserted into the block to limit spring expansion when working with very strong chime springs.
Preparing the winding block
Secure the block
Clamp the block firmly to the bench. Mainsprings exert significant force, and the block must not move during winding.
Remove the safety nails
The nails are used only when dealing with extremely strong springs. For standard strike springs, remove them before beginning.
Positioning the mainspring
Attach the loop end
Place the loop end of the mainspring over the nail or post on the block. This anchors the spring during winding.
Prepare the cable ties
Two cable ties linked together should be placed nearby. These will be slipped around the spring once it begins to compress.
Winding the mainspring
Use the let-down tool
Never use a winding key. A let-down tool provides a secure grip and prevents the arbor from slipping and injuring your hand.
Hold the great wheel firmly
Use your gloved hand to hold the great wheel down against the block. If it lifts or shifts, the spring can jump out of position.
Begin winding
Turn the let-down tool slowly and steadily. As the spring tightens, it will begin to draw inward toward the center post.
Insert the cable ties
Once the spring is partially compressed, slip the cable ties behind the loop end and around the spring. Tighten them gradually as you continue winding.
Continue winding and tightening
Alternate between winding the spring and tightening the cable ties. Maintain firm pressure on the great wheel at all times.
Let the spring settle into the ties
When the spring is fully compressed, slowly allow the let-down tool to unwind in your hand. The cable ties will now hold the spring securely.
Checking the spring fit
Test the loop end alignment
Place the loop end over the post to ensure the spring is compressed enough to fit back into the movement.
Adjust if necessary
If the spring is still too large, wind it slightly more and tighten the cable ties again.
Using safety nails for strong chime springs
When to use the nails
Triple-chime clocks have extremely strong mainsprings. If your hand becomes fatigued or begins to slip, insert the nails into the block.
How the nails help
The nails limit how far the spring can expand if you need to rest or reposition your grip. They act as a temporary containment barrier.
Maintain pressure
Even with the nails in place, keep your gloved hand firmly on the great wheel to prevent the spring from jumping out of the post hole.
Why winding in-hand is unsafe
Lack of control
Winding a mainspring in your hands leaves no way to insert a clamp or cable tie safely. You run out of hands immediately.
Risk of injury
If the arbor slips, the spring can unwind violently and cause serious injury.
Difficulty inserting clamps
Without a block, you cannot slide a mainspring clamp under the coils. The spring remains too tight and too unstable.
Frequently Asked Questions
Can I wind a mainspring without a block?
It is possible but unsafe. A block provides stability, containment, and a way to insert cable ties or clamps.
Why not use a winding key?
A winding key offers poor grip. If it slips, the spring can unwind instantly and injure your hand.
Are cable ties strong enough?
Yes. Quality cable ties are strong enough to contain a fully wound strike mainspring when tightened properly.
Do I need safety nails for all springs?
No. They are mainly for very strong chime springs. Strike and time springs usually do not require them.
Can I reuse cable ties?
No. Always use new ties. Old ties may have stress marks or weakened plastic.
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