Steps to Repair a Broken Wire on a Hermle Clock Balance Unit

(Data provided by claude.ai)

Steps to Repair a Broken Wire on a Hermle Clock Balance Unit

The Hermle floating balance uses a fine wire suspension system that can break. Here's a detailed guide to repairing it:

Understanding the Balance Wire System

The wire is 0.009" and a guitar string works as a replacement. A 0.010" fits but is too tight. The wire anchors are tricky - there are 2 anchors - but the wire doesn't meet itself or tie together. You wind around the anchors having stretched it straight to thread it through the tube.

Tools and Materials Needed

• Replacement wire: 0.009" diameter stainless steel wire (or 0.009" guitar string)
• Needle-nose pliers or tweezers
• Wire cutters
• Cleaning solution (lighter fuel, One Dip cleaner, or carb cleaner)
• Magnifying glass or loupe
• Steady hands and patience

Step-by-Step Repair Process

1. Remove the Balance Unit

• Carefully remove the balance assembly from the clock movement
• Work on a clean, soft surface to avoid losing small parts
• Handle the hairspring (if present) with extreme care to avoid distortion

2. Clean the Balance Unit Clean the balance first with carb cleaner then in One Dip cleaner. You can put the One Dip in a jar, place the floating balance in it, then put it in an ultrasonic with some water in it. One Dip is an excellent degreaser and will dry without any residue.

CAUTION: Never use oil on the balance wire system. The floating balance must remain completely dry except for any jewel oil at the pivot points.

3. Remove the Old Wire

• Carefully note how the original wire was threaded before removal
• Remove any broken pieces of wire from both anchor points
• Inspect the wire anchors (crimping slots) for damage

4. Prepare the New Wire Select a wire about 0.25mm (approximately 0.009") in diameter. Cut a piece longer than needed - you can trim excess later.

5. Install the New Wire - Bottom Anchor First Crimp the wire in the wire slot at the bottom of the bracket. This requires:

• Threading the wire end into the lower crimping slot
• Using pliers to gently compress the slot to secure the wire
• Ensure the wire is firmly held but not crushed

6. Thread Through the Balance Tube Wind around anchors having stretched it straight to thread through the tube:

• Thread the wire through the balance tube
• The wire passes through the center of the balance wheel assembly
• Keep the wire straight as you thread it

7. Secure the Top Anchor Pull the wire taut and crimp at the bracket top:

• Pull the wire tight but not excessively tight
• Secure it in the upper crimping slot
• Trim any excess wire

8. Adjust Wire Tension Adjust the tension by gently bending up the top of the bracket overhang. This is critical for proper operation.

9. Verify Proper Float Check to see that the whole unit truly floats on the spring. Neither the top nor the bottom of the balance tube should touch the bracket. The balance should hang freely on the wire without any contact.

10. Check Rotation You should have 180 degrees rotation each direction. The balance wheel should swing freely at least 180 degrees in each direction.

Testing the Repaired Balance

Balance Performance Test: Disengaged rotation from a 270 degree displacement should be 3-5 minutes. This means:

• Rotate the balance wheel 270 degrees (3/4 of a full turn)
• Release it and time how long it continues to swing
• It should continue oscillating for 3-5 minutes
• If it stops sooner, there's likely too much friction somewhere

Critical Checkpoints

Check the Guard Pin and Safety Roller: Check to see that the guard pin is not dragging inside or outside the C roller. A counterclockwise swing brings the guard pin just clear of the outside of the C safety roller. A clockwise swing brings the guard pin inside the C where it rides just clear again.

Verify Jewel Condition: Inspect the jewels at top and bottom for cracks or damage. Check the wire and jewel as both can cause problems.

Important Warnings

• Do not oil the balance wire system - Oil attracts dirt and creates friction
• Handle the hairspring carefully - Do not distort or otherwise damage the hairspring when handling
• Avoid violent temperature changes - Some people suggest using evaporating gas like Ether for cleaning, but this could crack the jewels via violent cooling

Alternative: Replacement Balance Units

If rewiring proves too difficult or the balance is damaged in other ways, complete replacement balance units are available. Complete floating balance assemblies are available for various Hermle movements including #130, #140, #150, #340, #350, and #1050 models. Many professionals recommend replacement over repair for worn units, as the newer balances often incorporate improvements.

Final Notes

This repair requires patience and a steady hand. If you're uncomfortable working with such delicate components, consider having a professional clock repairer handle it, or opt for a complete balance replacement. The rewiring process is technically feasible for a skilled hobbyist, but the critical nature of proper tension and alignment means there's little room for error.