Note: If you are one of the purists who thinks it is sacrilege to do anything other than restore old clocks to their original condition then you should stop reading right now.
I came across an old IBM schoolhouse style electric slave clock that wasn’t in working condition with the idea of keeping the clocks’ “look” original and using the existing hands, while converting it to a battery operated quartz movement.
Slave clocks were not designed to keep accurate time. They were designed to be hardwired to a master clock that would adjust the time on the slave clocks every hour.
After some searching on the web, I found several references to people who had converted an old IBM clock to a quartz movement, but very little in the way of how they did it. I sent a few emails out to the larger clock part suppliers found on the web, called a few (including a person who said they were a third generation clock maker) and they all said basically the same thing – you can’t keep the original hands from an electric clock when converting it to a quartz movement.
I decided to forge ahead and give it a try seeing that I already had a clock with a fried motor.
Disclaimer: I am not a clock maker. I have no previous experience working on clocks. None, Nadda. Zip. I am sure there is a better way to accomplish a conversion, but since those in “the know” haven’t had the time to share their secrets on the web, I will provide some information that may be of some benefit to others searching for quartz conversion instructions.
Large clock hands should use a “high-torque” quartz movement. I wanted the second hand to “sweep” vs “tick” to keep close to the “look” of the original clock. This means I needed a “continuous sweep” high-torque quartz movement.
Note: Continuous sweep on a quartz movement isn’t truly continuous – it give the impression of continuous by ticking many times per second). Seiko and Takane both make them.
I went with the Takane MVT312CHT as the total length of the hand shaft length was 7/8″ vs the 1″ of the original. I think a 3/4″ would have worked. I also ordered clock hour, minute, and second hands in as close to the original dimensions as the hands I had.
I couldn’t find any hands that looked close to the original IBM ones. If you aren’t particular, and you don’t care about using the original hands, then your conversion to quartz will be easy. Just store the original hands and use the new ones. I really wanted to use the original hands.
I first removed the back cover plate on the clock and took off all the screws to holding the motor and tubes. You have to remove the hands from the clock before you can finish removing the motor.
The IBM clock crystal on was held on by a steel bezel that circles the outer rim of the clock crystal like a giant spring. It just pulls off and I immediately placed the crystal in a safe place.
I removed the original hands. The second and hour hands are held on with nuts. The hour hand pulls up and off the shaft (this took some very determined wiggling to pry it off).
I compared the original IBM hands with the “new quartz hands” I had ordered and confirmed that none of the original IBM hands will work unmodified on the quartz movement. The hour hand hole is too small to fit onto the quartz movement shaft. The minute hand is round, and it needs to be rectangle in shape. The second hand on a quartz movement has a pin which pushes onto the quartz movement. The original IBM second hand slides onto the shaft and is held on with a small brass nut.
Modifying the Original IBM Clock Hands to Work on a Quartz Movement
This is how I accomplished it on my clock. This is not a “how to” but rather a “how did” – the end result could have easily gone wrong.
HOUR HAND – Enlarged the hole by drilling the center to the same diameter as the quartz hands that fit on the movement. This allowed me to push the hour hand onto the quartz movement.
MINUTE HAND – The original hand hole was round and it needed to be smaller and rectangle in shape. Apparently there are brass “collets” sold which go into the round hole and covert the hand to work on a quartz movement. I’ve seen them available in the U.K. but decided to try and MacGyver it to work. The hands I purchased were very lightweight aluminum. I simply cut the center off of the new hand and epoxied it to the back of the IBM hour hand. This made the hour hand a little thick to place it on the quartz shaft, but I was able to get the nut on to hold the hour hand in place.
SECOND HAND – The original second hand is made of aluminum with a brass center bushing (it looks like a button from the front). I removed the bushing by drilling it out. I then took the brass pin off of the quartz second hand I had ordered and it popped into the hole giving me a second hand that would simply push onto a quartz movement.
You can see the converted clock with the “continuous secondhand sweep” in action in the below video.
It keeps perfect time and there is no noticeable noise whatsoever. (I had read of complaints of loud noise with other conversions).
The only visual difference of the clock is that the second hand has a brass center while the original was painted all red. I could have painted it red, but decided to leave it as is.