Second Hand Setting Function

[Ethan Lipsig]

I have noticed that on some wristwatches and pocket watches, the second hand stops or runs backwards when setting the time back. This feature is useful in that it permits one to set a watch to the second. What is this feature called and how does it work mechanically?

[Cary Hurt]

Ethan,

I'm not aware of a watch where the seconds hand moves backward, but many watches, (often those primarily intended for navigation), are equipped with a feature wherein the seconds hand stops when the crown (or lever) is moved to the setting position. This is usually referred to as a hacking feature, and in most vintage wristwatches, it consists of some mechanism that actually stops the movement of the balance or the escape wheel. There are many ways to accomplish this, some more elegantly designed than others.

Regards,

Cary

[CZHACK]

If I understand correctly, a mechanical watch should never be set back but only forward (in particular for repeaters). Mike

[M. Cross]

Probably true for repeaters, Mike, but I've never heard that said regarding other mechanical movements. Someone posted not long ago an original Waltham advertisement stating it made no difference which way you turned the hands, as it would not harm a movement.

Regards! Mark

[Ethan Lipsig]

This is getting interesting. I can assure you that a C.H. Meylan I was setting this morning ran backwards as I applied a little backward torque to the crown while in the setting position. I know I have seen this happen frequently with wristwatches.

I never have understood there to be any harm in setting non-repeaters back in time.

[Cary Hurt]

Ethan,

I've seen watches whose seconds hand would reverse, at least briefly, but I'm not aware of that as a designed function. I will say that my experience with Meylan and similar grade watches is limited, and that watches of this stature sometimes include features that are beyond my understanding, both in purpose and design.

In hack-set wristwatches, the function often just involves a mechanical interference with the balance wheel. I recently dealt with a WW2 era Waltham, and the hacking device was a narrow spring stock finger that pivoted with the sliding set lever, coming into contact with the balance when the crown was pulled to the setting position.

And, like you, I have always believed the warnings about not setting mechanical watches (apart from repeaters) counter-clockwise to be carryovers from the world of clocks, where such things do indeed matter.

Regards,

Cary

[terry hall]

Old timers tell me that when the cannon pinion is too tight this will happen....

it is not a design feature... and IMHO different from the Hack mechanisms

[Tom McIntyre]

I am with Terry on this one. If the second hand goes backward, the watch needs service to loosen the cannon pinion.

[Ethan Lipsig]

Yikes. What I thought was a deluxe feature is turning out to be a significant problem. I asked my watchmaker for his views. He advised me that the defective cannon pinion is bad news all round. It tears up winding and clutch wheels. Tiny gears/delicate teeth, huge torques to force the cannon pinion to slip. Winding backwards is hard on the watch. The pinion even when slipping and adjusting hands in reverse puts a completely un natural force through the train all the way through the train to the escape. Sometimes it will cause the train to skip and run the watch in reverse. This is more commonly the case in certain wristwatch train layouts. It's not a feature as such more of a disaster in motion.

So, contary to what I had thought, there is a good reason not to set time backwards in nonrepeaters: if the cannon pinion is too tight, the parade of horribles my watchmaker described could happen.

[Don Dahlberg]

You can learn about the motion works here http://www.timezone.com/library/horologium/horologium0039

In a normal watch the center wheel arbor is attached to the cannon pinion by friction. The cannion pinion drive the minute hand and through a set of gears, the hour hand. When you put a watch into the setting position, another gear comes in connect the motion works to the winding stem and crown. This allows you to move the hands. In order that you not interact with the center wheel and the time train, the cannon pinion should slip. It does not matter which way you set a watch, because either way, the cannon pinion should slip and the train should still keep moving at the normal pace. Since the second hand is attached to the 4th wheel of the train, it should keep going at one revolution per minute.

If the cannon pinion is too tight and does not slip, then setting the watch would be driving the time train and do damage, but I cannot imagine that the escapement would allow it to run backwards.

Are there other systems where the second hand is part of the motion works rather than part of the train? If so, then it would run backwards with the minute and hour hands. I have never seen or worked on such a watch, but I only work on pre-WWII watches.

Don