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Discussion Starter · #1 · (Edited)
A little holiday gift to the forum. One of the more common questions I see on the Internet and in person is “What makes a hacking watch different?” The explanation is when the crown is pulled out the second hand stops so the watch can be synchronized to another time source. Further talk usually leads to the description of the iconic movie scene of soldiers or pilots huddled with their leader and synchronizing their watches to his mark.
Since one of my interests as a collector has been the American made movements that were used in the A-11 and FSS military watches, I have acquired examples from all four companies, Bulova, Elgin Hamilton and Waltham. I thought you might like to see the parts of each that actually do the legendary hacking.

First up is the movement I’ve shown before in my thread on Waltham collecting. In the Waltham 6/0 movements the hacking lever runs across the center of the train and terminates in a flat paddle that brushes against the ends of the balance wheel weights. Its other end rests against the tip of the winding stem.


Running position.

When the stem is pulled out for setting, its tip retracts and allows the hacking lever to rotate into the balance stopping it.


Hacking position.

The lever’s pivot and return spring lay in a machined recess that is not present on non-hacking movements. Everything is held in place by a screwed down plate.



Another well-known hacking movement is the Hamilton 987S which was used in their military watches as well as their civilian Sentinel and Secometer models (although being pre-war, I don't think the Sentinel had the hacking feature). The hacking feature of the 987S was similar to Waltham’s.


Running position.

The main difference is the lever is made from a curved piece of wire instead of being formed from a flat blade of metal. The end of the winding stem holds the lever away from the balance during normal running and allows a spring to push it into contact when pulled out for setting.


Hacking position.

Again everything lives in recesses cut into the pillar plate covered by a screwed down plate.



I have never seen a picture of the mechanical parts of Hamilton’s other famous hacking watch, the Bomb Timer. From descriptions I believe the hacking lever is not a part of the movement but a part of the case and contacts the outside edge of the 980 balance when depressed. Hopefully someone can add a pic of their case.

In my experience the most common and inexpensive hacking movement is the model 539 from Elgin. Elgin had massive war production and post-war it was put in civilian models as well as being recased by many jewelers and watchmakers. The 539 uses the basic lever brushing the balance wheel method but the lever is held to the pillar plate by a shouldered screw that also acts as its pivot. The spring is straight and is held in a slot in the plate by friction.


Hacking position.

Normally a 539 should have a special winding stem with a flat end instead of the usual pointed tip. As you can see here a regular stem works well enough but is not proper.


Running position.

In their later hacking movement, the 730A used in the B W Raymond RR model, Elgin simplified the hacking mechanism ever more. I don’t have a movement yet but this is a drawing from the Elgin Service Manual. The lever and spring are all one piece of bent metal that’s held aside by the end of the stem to allow the balance to beat.



I don’t supposed anyone here would be surprised that Bulova produced a bit of an odd duck as their A-11 movement. The 10AKCSH based on their 10AK movement with the addition of a center second train (CS) and a hacking feature (H). Instead of actuating the hacking lever with the end of the winding stem, Bulova added a pair of levers extending around the outside edge of the dial side of the movement.


Hacking position.


Running position.

An intermediate lever bears against the end of the set lever and its far end moves the hacking lever. The far end of the hacking lever extends through a hole in the pillar plate and contacts or releases the balance wheel. You can see the polished end of the hacking lever at the left side of these two photos as it touches and releases the balance weight.


Hacking position.


Running position.

This should let everyone pick out those little details in the seller’s pics that will verify that the hacking lever is present. You can usually catch a glimpse of the lever's tip under the main wheel next to the balance, or a bright dot by the rim of a Bulova balance. As far as whether a particular movement should hack: Waltham 6/0 ’42, -B and –C movements with center seconds all have the machining for the hacking parts although I have received some missing all the pieces. I believe but don’t know for sure that Hamilton made both hacking and non-hacking versions of the 987S. All Elgin 539s and some 532s are hacking movements. All Bulova 10AKCSH movements were hacking of course but there are no special markings to distinguish them from regular 10AKs and most of the mechanicals only show from the dial side.

Finally, I have a tip for anyone working on hacking movements, put the stem in the movement before trying to fit the balance. It saves a lot of time searching for the reason the balance isn't turning freely.

Joel
 

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Super Horology Joel!

Fantastic Joel...
Thanks for the great photos and wonderful
Horology!

Awesome stuff...:thumbup:

I put a link to this in the Library!
 

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Hack/ hacking

Great post- thanks. Now...

why did they choose the word HACK? Is it the Anglicizing of some fancy French term? :confused1:
 
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