Regulating a Rolex

Rolex Watch

My 16710T GMTII had been running a consistent +2 seconds/day fast since I owned the watch. After owning this particular watch for more than a year, I decided to take this project on myself. I have completed a few DVD watchmaking courses, and have completed both TimeZone Watchschool courses and have since rebuilt about a half-dozen mechanical watches. Subsequently, I don't feel too out of place working with an open Rolex case. Like with any project I take on, I do my research and ask a lot of questions. I was guided by a few folks who have contacted me via the website as well as through members of NAWCC (via email). Since I originally posted this page, my neighborhood Rolex watchmaker (who loves not too far from me) also gave me some pointers as well. I also knew that if I screwed it up, he could unscrew-it.

There are other ways to regulate the speed of a Rolex watch other than removing the caseback. With a Rolex registering 86,400 seconds every day, gravity can assist with keeping the watch on time. This image is frequently posted and referenced around the Internet as one method to use gravity to speed up or slow down a Rolex.

1. To gain a few seconds, lay the watch flat face-up overnight.

2. To lose a few seconds, lay the watch vertically with the crown downwards overnight.

3. To lose a few more seconds, lay the watch vertically with the crown up.

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Hannes puts it more succinctly with this great image. Face up = speed up; one-the-side = seconds slide.

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Mark M. Canon ("Turbinator" on Timezone.com and other watch-related sites) developed an Excel spreadsheet to measure a watch's accurracy. The Excel spreadsheet can be downloaded by clicking this link. Mark can be contacted at mcanon@gmail.com for comments or questions.

WatchTracker App for iOS

Tom Kerrington at roamingtrek@gmail.com makes a fantastic iOS app, Watch Tracker, that tracks timekeeping accuracy over the long term. This app is a must have for anyone who owns both an iPhone and a mechanical watch.

The iOS app is available here.

Despite these known methods for low-tech timing measurement, I decided to adjust the balance such that it is precise. On a Rolex, this is easier said than done. This version of the GMTII uses Rolex's 3185 movement. Like all Rolex movements, the balance wheel is "free-sprung" whereby the balance wheel moves freely without anything inhibiting its rotation. Rolex, Patek, non-ETA Panerai's, as well as a few other watch companies use a free-sprung balance wheel rather than using a regulated balance. Regulated balances are easy to identify as one will see a + or - next to the balance wheel, usually on the balance bridge/cock and an adjusting mechanism that rotates the balance jewel slightly allowing the balance to be slowed down or sped up. ETA and its derivitives use a regulated balance and is prevalent on many top quality watches.


Rolex Watch Regulation BalanceFree-sprung balance wheels are also readily recognizable as the balance wheel either has weights, such as Patek, or adjustable screws in them. Rolex uses four Microstella screws that are two different sizes opposing each other on the balance wheel. Adjusting these small screws requires specialized tools and a steady hand, much more so than adjusting a regulated movement such as the mechanisms found on ETA.

This image shows a Rolex balance wheel and two of the four Microstella screws. The screw on the right is the smaller screw for one-second adjustments, and the larger screw for two-second adjustments is on the left.


Rolex Watch Tool
Microstella Wrench

Adjusting a Rolex balance wheel requires a Microstella wrench. There are two schools of thought on which type of wrench to use. There is the traditional Rolex Microstella wrench (or knock-offs that are very similar). This wrench has an adjustment indictor built into the wrench that shows how much to turn the wrench. Once notch in the wheel = one second adjustment when completed on a pair of screws. This wrench is intended to adjust the Microstella screws while the balance while is mounted in the watch.


Rolex Watch WrenchThere is also this relatively standard type of wrench. The producer of this wrench says that it is best to remove the balance to make adjustments as it is possible to break a balance staff while making adjustments. Removing the balance assembly reduces the possibility of breaking the balance staff while making adjustments. Between the two wrenches, I prefer using the standard Microstella wrench because of the adjustment indicator and I find it is easier to position the wrench onto the Microstella screw.


Tools & Background

After initially posting this page, a number of watchmakers commented on that I am missing a few tools. To do this procedure absolutely correctly requires a pressure tester so that the cased movement is as waterproof as it was prior to opening, and secondly, a timing machine to measure beat rate, beat error, and amplitude. Amplitude (the amount the balance swings in each direction) is important as this will tell you how much variance there is going to be when the watch is face up, face down, and in various other positions. In this .wmv clip on overhauling a 1570 movement, you will see the use of a timing tool. Without a timing tool, you are timing in the dark. (click for larger image).

A great manual describing how to use a timing machine and all the variables involved is posted here.


Rolex Watch Balance Tools

The tools required are similar to the tools reqired for removing a Rolex caseback. In addition to the caseback removal tools there are also a Microstella wrench, and a Dumont #7 pair of watchmakers tweezers required for this procedure. The Dumont #7 tweezers differ than the norm because the point curves. These tweezers are used to hold the balance wheel while the Microstella wrench turns the screws. These tools are available from Otto Frei, Jules & Borel, as well as other watch supply houses.



The Microstella screws are designed such that if the screw is adjusted inward, the balance speeds-up, similar to an ice-skater doing a spin; skaters bring their leg in to speed up. The screw adjusted outward towards the balance wheel rim will slow the balance down.

An adjustment on a small screw = 1 second/day and an adjustment on a large screw = 2 seconds/day

Any adjustment on one screw requires the same adjustment on the opposing screw or else the balance will be adjusted out of poise.

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(click scans for larger size) Scans from Tony Axelzon, used with permission.




To determine how much to turn the screw, the wrench has an index marked by a freely moving balanced indicator inside the wrench. This vintage image illustrates the wrong way to hold the wrench and the balance. The tweezers are not supported and can easily break the balance staff.



This image from the Rolex Factory Service brochure that is included in the latest Rolex packaging shows more than what Rolex does to regulate a watch; it shows how to hold the tweezers to keep the balance steady. This watchmaker is using the balance bridge to steady the tweezers. Use the balance bridge to guide the tweezer tongs onto the balance wheel.

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Okay... The Steps

Before removing the caseback (steps here), first detemine how much ajdustment watch requires and calculate whether one has to adjust the larger screws (two-seconds a notch in the Microstella wrench) or the smaller screws (one-second a notch). Then, secondly, determine whether you have to turn the screws inward to speed up the balance, or outward towards the rim of the balance wheel to slow down the balance. I found that making adjustments to the larger screws first makes the biggest difference.

Turning the screw clockwise = screw going inward = speed up
Turning the screw counter-clockwise = screw going outward = slow down

Practice using the Microstella wrench and determine how far and in what direction you need to turn the screws before actually adjusting the balance, similar to how a golfer does practice swings before going to the tee.

Unscrew the winding crown, and pull it out all the way such that the second hand, and the balance stops.


Using a workspace that allows your eyes to be at the same level as the balance (eg a high steady table), carefully rotate the balance using the #7 tweezers to the screw that requires adjusting.

Rolex balanve wheelBe sure to notice the two divet locations (red arrow above) for you to discern the opposite Microstella screw. Sometimes the balance wheel will slip free and spring back-and-forth, losing your reference on which Microstella nut you were adjusting.

Be sure not to touch the hairspring. There is plenty of room beween the balance and hairspring, but do not be fully caffienated with coffee when doing this procedure. Additionally, be sure to be using a loupe so you can see the wrench being slipped onto the Microstella screw.

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Steady the balance by using tweezers before turning the screw. Use the balance bridge to steady the tweezers as noted by the blue arrow. Then carefully slide the Microstella wrench onto the nut (black arrow) and turn the screw the direction required. When doing this, look at the amount that the screw is being turned as practiced with the golf swings above.

When the first nut is adjusted, then gently rotate the balance to the opposite side of the balance and repeat the same steps. The balance will move slowly as it is being braked. remember the location of the divets in the balance wheel spoke (red arrow) which will help you remember which nut you adjusted. There are only two of these divets marked on the balance wheel.

Update: I found that after some practice, I did not need the use of the tweezers. I would use the Microstella wrench to move the balance (albeit very gently) 180 degrees to adjust the opposite screw.

Once completed, depress the crown so that the balance runs freely and replace the caseback. Do not fully tighten the caseback as there will probably be some further adjustments with perhaps the smaller Microstella nuts after placing the watch on the timing machine (mentioned below). It took me three tries before I found the correct combination. After replacing the caseback, wear the watch for a full 24 hours before determining whether more adjustment is necessary and before fully closing the caseback.

After adjusting my watch, there is a definite feeling of accomplishment. Akin to open heart surgery, this procedure does take a steady hand, clear head, and the proper tools, but it is possible for watch owners to regulate their own Rolexes. The procedure was easier than picking any of the parts in the Operation game. If you can play this game without the buzzer going off, you certainly can turn the Microstella on a Rolex balance.



Update: I purchased a TYMC timing machine from Orbita and it is a great little device. Below is an image of my GMT 116710 on the machine. By the looks of it, no regulation is required.

This is the screen with the 116710 face up. The S/d is standard deviation / Day. The 308 degrees is amplitude, and the beat error is .1ms, very well within specification.

Timing Machine