A company called Horolovar makes suspension springs for 400 day clocks. Various thicknesses are available. If the spring is too thick the clock will gain time, and if too thin it will lose time
Suspension Spring Thickness for Schatz 400 Day and 1000 Day Clocks
Schatz clocks have a model number inside a circle on the back plate (49, 53, 54 or JUM/7). The other numbers on the back of a Schatz clock are the date code (month and year). Here are the suspension spring thicknesses for Schatz 400 day and 1000 day clocks:
- Schatz standard size clock (49 on back plate): .004 inch
- Schatz miniature (53 on back plate): .0023 inch (Note 4-8-12: I now recommend a 0.0024 inch thick spring)
- Schatz 1000 day clock (54 on back plate): .0024 inch
- Schatz midget 400 day clock (JUM/7 on back plate): .0022 inch
Suspension Spring Thickness for Kundo 400 Day Clocks
- Kundo full sized clock (about 12″ tall): .0032 inch
- Kundo miniature clock (about 9″ tall, including the oval base model): .0023 inch (Note 4-8-12: I now recommend a 0.0024 inch thick spring)
- Kundo midget (similar to the miniature but the anchor pin has an offset bend and makes contact with the fork slightly behind the back plate): .0022 inch
For other clocks, you will need the Horolovar 400 Day Clock Repair Guide to determine the proper spring thickness. Note: measuring the old spring’s thickness is not a reliable method, as the spring may not be a Horolovar brand spring. The Repair Guide and suspension springs are available from Norkro.com and other clock parts suppliers.
The thicknesses given above are for genuine Horolovar suspension springs, which most clock suppliers sell. You may want to ask to be sure you are getting Horolovar suspension springs.