Clock Key Sizes – Everything You Need to Know

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When it comes to winding and setting antique or vintage clocks, having the right tools is essential. Clock keys play a crucial role in ensuring the smooth operation of these timepieces. In this article, we will delve into the world of clock key sizes and provide you with all the necessary information to understand, choose, and use the correct key for your clock.

Understanding Clock Keys

What are Clock Keys?

Clock keys are specialized tools used to wind and set various types of clocks. They typically consist of a handle or shaft and a removable bit that matches the shape and size of the clock’s winding arbor or keyhole. Clock keys are available in different sizes to accommodate the diverse range of clocks available.

Importance of Clock Keys

Clock keys are essential for maintaining the proper functioning of mechanical clocks. They allow you to wind the clock’s mainspring, which stores the energy necessary for the clock’s movement. Additionally, clock keys are used to set the time and perform other adjustments on certain clocks.

Common Clock Key Sizes

Small Clock Key Sizes

Small clock keys are typically used for petite or delicate clocks, such as mantel clocks or carriage clocks. These keys are often labeled with numbers ranging from 1 to 5, with 1 being the smallest size. Small clock keys are usually less than 2 inches in length.

Medium Clock Key Sizes

Medium clock keys are commonly used for wall clocks and larger mantle clocks. They are labeled with numbers ranging from 6 to 10, with 6 being smaller than 10. Medium clock keys generally measure between 2 to 3 inches in length.

Large Clock Key Sizes

Large clock keys are designed for floor clocks, grandfathers, and other large, weight-driven clocks. They are labeled with numbers from 11 to 14, with 11 being smaller than 14. Large clock keys typically measure over 3 inches in length.

How to Determine the Correct Clock Key Size

Measuring the Clock Keyhole

To determine the correct clock key size, you can measure the keyhole of your clock. Use a caliper or ruler to measure the width and depth of the keyhole. Compare these measurements to the specifications provided by clock key manufacturers to find the appropriate size.

Consulting the Clock Manufacturer

If you’re unsure about the correct key size, it’s always best to consult the clock manufacturer or an experienced horologist. They can provide you with accurate information and recommendations based on the specific make and model of your clock.

Where to Find Clock Keys

Clock Specialty Stores

Clock specialty stores often carry a wide range of clock keys, catering to different sizes and types of clocks. These stores have knowledgeable staff who can assist you in finding the right key for your clock and offer expert advice on maintenance and repairs.

Online Retailers

Online retailers provide convenient access to clock keys. Many reputable websites offer a comprehensive selection of clock keys, making it easy to browse different sizes and compare prices. When purchasing online, ensure that the retailer has a reliable return policy and good customer reviews.

Antique Shops

Antique shops and flea markets can sometimes be treasure troves for clock enthusiasts. They may have vintage or specialty clock keys that are not readily available elsewhere. However, it’s important to exercise caution and ensure that the key fits your clock properly before making a purchase.

Tips for Using Clock Keys

Handle with Care

Clock keys are delicate tools that require gentle handling. Avoid applying excessive force while winding or setting the clock. Always turn the key smoothly and steadily, ensuring you do not damage the winding arbor or keyhole.

Proper Alignment

When inserting the clock key into the keyhole, make sure it aligns correctly with the winding arbor. Misalignment can lead to key slippage or damage to the key and the clock mechanism. Take your time and ensure a proper fit before turning the key.

Regular Maintenance

Regular maintenance is essential for the longevity of your clock. Clean the clock key regularly to prevent the buildup of dirt and grime. Additionally, consider professional clock servicing at regular intervals to ensure optimal performance and prevent any potential issues.


Clock keys are vital tools for maintaining the functionality of mechanical clocks. By understanding the different sizes, determining the correct size, and using them properly, you can ensure your clock runs smoothly for years to come. Remember to handle clock keys with care, seek expert advice when needed, and keep up with regular maintenance to enjoy the timeless beauty of your clock.


What if I can’t find the exact clock key size?

If you can’t find the exact clock key size, it’s generally recommended to choose the closest size available. However, it’s essential to exercise caution and ensure a proper fit to avoid damaging the clock mechanism. Consulting a clock specialist or the manufacturer can provide further guidance.

Can I use a different size clock key?

Using a different size clock key is not ideal, as it may lead to improper winding and potential damage to the clock. It’s best to use the correct key size whenever possible to ensure the smooth operation and longevity of your clock.

Are clock keys universal?

Clock keys are not universal. The size and shape of clock keyholes can vary between different clock models and manufacturers. It’s crucial to find the right key that matches the specific clock you intend to use it with.

How often should I replace my clock key?

Clock keys are durable tools and do not typically require frequent replacement unless they become damaged or lost. However, regular maintenance and cleaning are essential to keep the key in good condition and ensure it functions properly.

Can I use a clock key on a non-clock object?

Clock keys are designed specifically for winding and setting clocks. Using a clock key on a non-clock object may not be suitable, as the key may not fit properly and could potentially cause damage. It’s best to use clock keys solely for their intended purpose.

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