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Seconds at 6, explained
I have seen a number of questions asked over the years about what the “seconds at 6†issue is. I’ve also seen a lot of misstatements by members about whether or not seconds at 6 will impact the watch you are considering. To put the issue to rest, I wanted to piece together a post from other older posts that will consolidate the relevant information. I am not a watchmaker by any stretch, and the information below is information found on this very site, and is already available. It is taken from other members also, and credit has been given to them for photo's and quotes where applicable.
Also, I have never owned a seconds at 6 watch, so I dont have personal experience with it.
What is the seconds at 6 problem?
The Asian 7750 mechanical chronograph movement is designed with running seconds at the 9 o’clock position. To cause the subdial at 6 to act as the running seconds indicator, a gear train must be installed and the movement must be modified. The same thing must be done in the case of a seconds at 12 o’clock movement too.
Here is what truster watchsmith 14060 or 16610? had to say in a thread about the original A7750 movement:
for starters, here is a look at the "old-style" seconds-at-6 A7750. The running seconds transfer gears are crudely fashioned, with wheels that just revolve around press-fit pivots. This design lends itself to a higher friction load which, coupled with the inevitable A7750 dirt and grit, can eventually just freeze the movement up (more friction than the geartrain can overcome). Another common problem is that the pivots could actually come loose, leading to misaligned or dislodged transfer gears. So historically these movements, straight from the factory, kept poor time (extremely affected by position) or just stopped altogether.
Below are some pictures also taken from 14060 or 16610?’s thread where the gear train can be seen.
What kinds of watches are impacted by the seconds at 6 problem?
Only watches with Asian 7750 mechanical chronograph movements, that have the running seconds on the subdial at 6 o’clock.
Chronographs with seconds at 9 are not affected.
Quartz watches are not affected, such as my IWC Ingenieur Quartz.
Non-chronographs with running seconds at 6 are not affected, such as hand-wind models like the Omega Railmaster or IWC F.A. Jones.
Seagull ST-19 chronograph movements, aka Venus Lemania (not debating the accuracy of this other moniker)
What are some watch models that are affected by the seconds at 6 problem?
Rolex Daytona
IWC Portuguese Chronograph
IWC Ingenieur Chronograph
Audemars Piguet Royal Oak Offshore Chronographs with seconds at 12
Are there modifications that can be made to make a seconds at 6 watch more reliable?
Graphite treatment
Graphite can be applied to the gear train to relieve some of the friction that can cause the movement to run slowly or stop. This is a temporary fix as eventually the graphite will be worn through.
Jewel modification
Additional jewels can be added to the gears in the gear train to reduce friction. This is a relatively expensive modification and it is very time consuming, but it appears to be a much longer-term solution than graphite treatment.
What about the newer 29 jewel movements that say they do not suffer the seconds at 6 problem?
According to 14060 or 16610? in his aforementioned post, the new movement essentially adds additional jewels to the gear train, just like the jewel mod mentioned directly above. His post summarized is that the movement appears to be working well in the watches he has serviced. However, he also notes that “there is still the matter of getting the gear heights adjusted precisely and taking steps to prevent pivot separation. The newer movement is no different from the old in these areas, and it requires skill and precision to get everything just right.†The pictures below are again from his post on the topic.
Jewel modded movement
Gears with their added jewels
Reference threads
Bonesey’s Rolex Daytona / Yacht-Master I & II Guide
The "New and Improved" Seconds-at-6 Movement Explained
By-Tor’s Review, FAQ& buying guide of ROLEX Daytona "Seconds at 6"
Domi’s time bomb solved, explaining the jewel mod
I have seen a number of questions asked over the years about what the “seconds at 6†issue is. I’ve also seen a lot of misstatements by members about whether or not seconds at 6 will impact the watch you are considering. To put the issue to rest, I wanted to piece together a post from other older posts that will consolidate the relevant information. I am not a watchmaker by any stretch, and the information below is information found on this very site, and is already available. It is taken from other members also, and credit has been given to them for photo's and quotes where applicable.
Also, I have never owned a seconds at 6 watch, so I dont have personal experience with it.
What is the seconds at 6 problem?
The Asian 7750 mechanical chronograph movement is designed with running seconds at the 9 o’clock position. To cause the subdial at 6 to act as the running seconds indicator, a gear train must be installed and the movement must be modified. The same thing must be done in the case of a seconds at 12 o’clock movement too.
Here is what truster watchsmith 14060 or 16610? had to say in a thread about the original A7750 movement:
for starters, here is a look at the "old-style" seconds-at-6 A7750. The running seconds transfer gears are crudely fashioned, with wheels that just revolve around press-fit pivots. This design lends itself to a higher friction load which, coupled with the inevitable A7750 dirt and grit, can eventually just freeze the movement up (more friction than the geartrain can overcome). Another common problem is that the pivots could actually come loose, leading to misaligned or dislodged transfer gears. So historically these movements, straight from the factory, kept poor time (extremely affected by position) or just stopped altogether.
Below are some pictures also taken from 14060 or 16610?’s thread where the gear train can be seen.
What kinds of watches are impacted by the seconds at 6 problem?
Only watches with Asian 7750 mechanical chronograph movements, that have the running seconds on the subdial at 6 o’clock.
Chronographs with seconds at 9 are not affected.
Quartz watches are not affected, such as my IWC Ingenieur Quartz.
Non-chronographs with running seconds at 6 are not affected, such as hand-wind models like the Omega Railmaster or IWC F.A. Jones.
Seagull ST-19 chronograph movements, aka Venus Lemania (not debating the accuracy of this other moniker)
What are some watch models that are affected by the seconds at 6 problem?
Rolex Daytona
IWC Portuguese Chronograph
IWC Ingenieur Chronograph
Audemars Piguet Royal Oak Offshore Chronographs with seconds at 12
Are there modifications that can be made to make a seconds at 6 watch more reliable?
Graphite treatment
Graphite can be applied to the gear train to relieve some of the friction that can cause the movement to run slowly or stop. This is a temporary fix as eventually the graphite will be worn through.
Jewel modification
Additional jewels can be added to the gears in the gear train to reduce friction. This is a relatively expensive modification and it is very time consuming, but it appears to be a much longer-term solution than graphite treatment.
What about the newer 29 jewel movements that say they do not suffer the seconds at 6 problem?
According to 14060 or 16610? in his aforementioned post, the new movement essentially adds additional jewels to the gear train, just like the jewel mod mentioned directly above. His post summarized is that the movement appears to be working well in the watches he has serviced. However, he also notes that “there is still the matter of getting the gear heights adjusted precisely and taking steps to prevent pivot separation. The newer movement is no different from the old in these areas, and it requires skill and precision to get everything just right.†The pictures below are again from his post on the topic.
Jewel modded movement
Gears with their added jewels
Reference threads
Bonesey’s Rolex Daytona / Yacht-Master I & II Guide
The "New and Improved" Seconds-at-6 Movement Explained
By-Tor’s Review, FAQ& buying guide of ROLEX Daytona "Seconds at 6"
Domi’s time bomb solved, explaining the jewel mod
