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Mechanical Clock Keys
Mechanical clock keys are the clock parts that are most frequently lost. Once the clock key is no longer with the clock, it always seems to disappear. With the below information you can order a new key utilizing the clock key size chart.
Getting the Right One
We have mechanical clock keys in all the sizes available. Between the key chart or the movement type information below, you have a good chance of finding the perfect key. The movement type includes if the clock is made in Germany or USA and when it was made.
This is the fastest and most easiest way to get the clock key. The further back in time we go with clocks, the more we would need to rely on the key chart instead. There will be a stamp with the country of origin on the back plate of the movement and this can help us get the key.
Clock Key Size Chart Explanation
- 1.75mm = 000 Key
- 2.0mm = 00 Key
- 2.25mm = 0 Key
- 2.5mm = 1 Key
- 2.75mm = 2 Key
- 3.0mm = 3 Key
- 3.25mm = 4 Key
- 3.5mm = 5 Key
- 3.75mm = 6 Key
- 4.0mm = 7 Key
- 4.25mm = 8 Key
- 4.5mm = 9 Key
- 4.75mm = 10 Key
- 5.00mm = 11 Key
- 5.25mm = 12 Key
- 5.5mm = 13 Key
- 5.75mm = 14 Key
- 6.0mm = 15 Key
Clock keys have there own number system from 000 to 16 as seen in the Clock key size chart. However the number does not indicate what size is what number and can be confusing. So how do you use the Clock key size chart to get the right key?
It would make more sense if the key size was the MM of how wide the key was to fit, but this is not how it works. This section is to figure out what key number to order so the clock can be wound up. Subsequently, the clock key gets lost the most out of any other clock part.
Of course, it can be tricky to find the right key for your clock because there are many sizes. The Clock key size chart will give us the right size key to order.
Double End Clock Keys
In addition, some keys have two sizes on one key and this is called a double end key. By and large, the clock key size chart will work for both the wind up part of the clock and also the smaller F / S portion. When the clock has a F / S regulator portion it will be at the 12 o’clock on the dial.
Alternately, if there is a small arbor inside of a hole at 12, this is the time regulator control and the key would have two ends. Thus, it may say F / S at this location or A / R. F / S stands for Fast or Slow, or it could say A / R to stand for Advance or Retard and is referring to the timing of the clock.
Of course, if the clock is running fast in time, turn more to the Slow or Retard direction to slow it down. Refer to the Clock key size chart with your measurements to find a key to work with this function.
Getting the Right Clock Key Size
Given these points, to get the key needed, measure the shaft the key is to go on to, then use the Clock key size chart to get the key size needed.
Please do not call asking what key the clock needs, as you will be told it would still have to be measured. In short, measure the shaft that the key goes onto in MM and then use the clock key size chart to match it up.
The Lazy Way Instead of the Clock Key Size Chart
The Clock key size chart has all of the sizes listed however sometimes certain key sizes are known. Generally speaking, almost all post 1960 mechanical clocks, made in Germany take a size #8 key or crank, unless the movement is round.
Ordinarily the round ones take a number 4. The American time strike antique units mostly take the size 7 key. Match your measurements to the Clock key size chart to be sure.
How to find the Right Key for Hermle Movements
Clock Key Required by Hermle Movement Number
Use this Clock Key Chart to quickly identify the correct key number and type based on your Hermle movement ID number. Ensure a perfect fit for winding your clock!
Keys for German Units Post WW2
German made post WW2 movements that are square or rectangle will take a number 8 key or crank.
If the clock movement is round and made in Germany the key size is number 4. Some round ones will take a number 3 but if getting a 4 it will still fit and wind the clock either way.
Keys for USA Units 1900 – 1950
American clocks made from around 1875 until after the second war almost always take the size 7 clock key. The number 7 keys fits the 8 day time / strike units pretty much every time and this is what USA made the most of. This rule may not apply to Westminster (3 places to wind) or time only (one place to wind) clock movements.
Keys for Korean and Chinese Clocks
Size 7 for these units usually. All the 31 day clocks with Asian movements and also US replicas made in India, all take size 7.
The Over Wound Myth
Of course, if a clock is not working, people wind it up all the way in attempts to make it run. Everyone winds it up, but the clock still doesn’t work, so it remains wound up.
The only way a clock can be overwound is if someone winds it up for so long that the mainspring becomes stuck.
How Do I Know What Size My Clock Key Is?
Understanding the correct size of your clock key is crucial for maintaining and operating your timepiece. The key size affects how well you can wind the clock and keep it running smoothly. If you’re unsure about your clock key size, this guide will help you determine the right one and ensure your clock remains in good working order.
1. Why Is Knowing Your Clock Key Size Important?
Understanding the size of your clock key is essential for several reasons. First and foremost, the right key ensures that you can wind your clock efficiently. If the key is too small, it won’t grip the winding arbor correctly, making it challenging to wind the clock. Conversely, a key that is too large may slip, potentially damaging the clock’s mechanism. Therefore, knowing your clock key size prevents unnecessary wear and tear on your clock and ensures accurate winding.
2. How Are Clock Key Sizes Measured?
Clock keys are typically measured using a standardized numbering system. This system ranges from small to large, with each size corresponding to a specific measurement in millimeters. The size is determined by the diameter of the clock’s winding arbor, which is the part of the clock where the key fits. For instance, a size 6 key fits a winding arbor with a diameter of 3.75 millimeters. By measuring the arbor, you can accurately determine the correct key size.
3. What Tools Do I Need to Measure My Clock Key Size?
To measure your clock key size, you will need a few simple tools. A caliper or a precise ruler is ideal for measuring the diameter of the winding arbor. Additionally, you may use a clock key gauge, a tool designed specifically to measure clock key sizes. By using these tools, you can determine the exact size of your winding arbor, ensuring that you select the correct key.
4. Step-by-Step Guide to Measuring Your Clock Key Size
Determining your clock key size involves a straightforward process. Here’s how you can do it:
- Locate the Winding Arbor: First, identify the winding arbor on your clock. This is usually found on the clock’s face, where the key is inserted for winding.
- Measure the Arbor’s Diameter: Using a caliper, carefully measure the diameter of the arbor. Ensure the caliper is placed accurately to avoid any errors in measurement.
- Consult the Key Size Chart: Once you have the measurement, consult a clock key size chart. Match your measurement with the corresponding key size. For example, if your arbor measures 3.75 millimeters, you’ll need a size 6 key.
- Test the Key: If possible, test a key of the determined size on your clock. It should fit snugly, with no slipping or difficulty in turning.
5. What If I Don’t Have the Original Key?
If you’ve lost the original key or never had one, don’t worry. You can still find the correct size. Measure the winding arbor as described above and use the measurement to select a new key. It’s important to get the size right the first time to avoid damaging your clock.
6. Where Can I Purchase the Correct Clock Key?
Once you’ve determined the correct size, you’ll need to purchase a replacement key. At Clockworks.com, we offer a wide range of clock keys in various sizes to suit different types of clocks. Whether you need a standard size or a specialty key, you can find it in our catalog. Simply visit our website, navigate to the clock keys section, and select the size you need. We provide detailed descriptions and specifications for each key, making it easy for you to find the perfect match.
7. How Can I Ensure Longevity and Proper Maintenance of My Clock Key?
Proper maintenance of your clock key is as important as knowing its size. After every use, ensure that the key is stored in a dry place to prevent rust. Additionally, avoid using excessive force when winding your clock, as this can wear down the key and the winding arbor. Regular maintenance of both the clock and the key will ensure they last for years to come.
8. Are There Different Types of Clock Keys?
Yes, there are several types of clock keys, and each serves a different purpose. The most common are double-ended keys, which have different sizes on each end for winding and setting the time. Some clocks, especially antique ones, may require specialized keys. It’s essential to identify the type of key your clock requires before making a purchase. At Clockworks.com, we offer a variety of key types to match your specific needs.
9. What Should I Do If My Clock Key Doesn’t Fit Properly?
If you find that the key doesn’t fit properly, it could be due to several reasons. First, recheck the arbor’s diameter to ensure you’ve measured correctly. If the measurement is correct and the key still doesn’t fit, there may be an issue with the clock’s winding mechanism. In such cases, it’s best to consult with a clock repair expert. At Clockworks, we not only sell parts but also offer clock repair services. You can contact us at [email protected] for assistance.
10. Final Thoughts
Knowing the size of your clock key is fundamental to the proper functioning and maintenance of your timepiece. By following the steps outlined above, you can easily determine the correct key size and avoid potential damage to your clock. For a wide selection of clock keys and expert advice, visit Clockworks.com. We’re here to help you keep your clock ticking smoothly.
I have a Seth Thomas clock that is super heavy. It was manufactured for stowell & co and dates back between 1890-1910. The key has been lost and was wondering what size I need for it
How wide, in MM, is from one flat side of the winding arbor to the other side?
James Stoudenmire
40yr Clockmaker
Author of Clockworks.com
I need a #10 key or key crank for a Paul Rogers & Son, Berwick, ME Grandfather Clock.
Please advise options?
Thank you.
This one, size 10
https://www.clockworks.com/product/grandfather-clock-key-crank
James Stoudenmire
40yr Clockmaker
Author of Clockworks.com
Where exactly do I find the key chart?
The Clock key size chart has all of the sizes listed however sometimes certain key sizes are known. Generally speaking, almost all post 1960 mechanical clocks, made in Germany take a size #8 key or crank, unless the movement is round.
Ordinarily the round ones take a number 4. The American time strike antique units mostly take the size 7 key. Match your measurements to the Clock key size chart to be sure.
1.75mm = 000 Key
2.0mm = 00 Key
2.25mm = 0 Key
2.5mm = 1 Key
2.75mm = 2 Key
3.0mm = 3 Key
3.25mm = 4 Key
3.5mm = 5 Key
3.75mm = 6 Key
4.0mm = 7 Key
4.25mm = 8 Key
4.5mm = 9 Key
4.75mm = 10 Key
5.00mm = 11 Key
5.25mm = 12 Key
5.5mm = 13 Key
5.75mm = 14 Key
6.0mm = 15 Key
The content of this website is copyright by Clockworks and written by James Stoudenmire in year 2022