IBM Simplex Schoolhouse Clock Conversion to Quartz

IBM Clock

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.

IBM Clock Hands

Original IBM Clock hands.

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.

IBM Clock

Back of clock with cover.

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.

IBM Clock Movement

Original IBM clock movement (rear view).

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.

IBM Clock Hands

Hour and minute hand after second hand was removed.

IBM Clock Hands

Side view of hour and minute hand.

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.

IBM Hour Hand

Hour hand hole drilled larger for 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.

IBM Minute Hand

New minute hand. Cut centerpiece to be epoxied to back of original minute hand.

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.

IBM Second Hand

Top and side view of new second hand. Brass head was removed for use in original red second hand.

You can see the converted clock with the “continuous secondhand sweep” in action in the below video.

IBM SIMPLEX Schoolhouse Clock Quartz Conversion

It keeps perfect time and there is no noticeable noise whatsoever. (I had read of complaints of loud noise with other conversions).

IBM Clock

Quartz movement in place.

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.

IBM ClockIBM Clock

19 thoughts on “IBM Simplex Schoolhouse Clock Conversion to Quartz

  1. Nice job.. Definitely like the McGuyver approaches; good solution and great result.
    Might be nice to mention the epoxy you used; it’s so easy to go wrong with choice of epoxy.

    1. Hello,

      Great job! Can you tell me which hands you ordered for the Mcguyvering?
      I’m looking to do the same, unless you know where to order the collet from.

      1. You want to go with hands that will fit the shaft of the movement. To fit the MVT312CHT movement, I used HND1351 & 68024 from I think the hands were $1 each.

  2. I just wanted to thank you for the brilliant idea of epoxing the section of hands that fit into the Quartz movement you’re buying to replace the electric clock movement. I recently purchased a beautiful Telenorma industrial clock with a very distinctive hour hand that I did not want to give up, yet it wouldn’t fit on conventional Quartz movements, until now, thanks to you. Kudos.

    1. There is a nut that comes with the movement that screws from the front face (you can see it on the side view of the clock) that holds the movement in place. If you have problems with it moving, I would just use a little clear silicone on the back of the movement, but I didn’t use anything.

  3. Thanks for writing this up! I’ve been wanting to convert an old Simplex clock for years but haven’t been able to find any kind of help. Last night I finally did it using your steps and all the same parts listed here. Everything went exactly as you describe except when I tried to drill out the hour hand the bushing also came leaving too big of a hole. I simply repeated your minute hand hack and epoxied the new center hole onto the old hour hand.

    Now it’ll just take some getting used to. The dangling cord was very much a part of our kitchen…

  4. Love your clock! Would love to find that same IBM model and do the conversion. What model number is the clock? Thanks for taking the time to post all of this. Very much appreciated!

  5. Awesome! I have 2 of the IBM clocks and currently I just have one wired to a lamp cord and plugged into an AC outlet in my office. I love the IBM logo and sweeping hand. To set it I just wait until the time is right and plug it in. I am definitely ordering one of those sweeping quartz movements and doing a conversion!

  6. Thanks for all the info. I pulled this off but had to go off road for a couple of steps: 1.) On the hour hand there was this little cap on the front side that completely popped off as I was trying to drill the hole larger so I just used the same approach as on the minute hand (with my replacement hour hand); and 2.) I mangled my original second hand so I used the replacement second hand – cut it to length and painted it red. It does not have the same taper as the original but doesn’t look too bad. One thing that takes some patience is adjusting the bends on all the hands so they’ll clear each other and not hit the glass (minute and second hands) – this had me pulling my hair out but I finally got it. Lastly, I used JB Weld (cold weld formula) – comes in a package with a black and red tube.

  7. This is great info. How did you remove the front glass to get access to the hands?

    It looks like there is a sprint around the circumference of the face that could be pulled out to release the glass, but not sure. Is this right?

    1. Yes, you remove the spring. It takes a little practice to get the spring back in, but wasn’t too difficult.

        1. It’s been some time since I did it, but I held one end in place while feeding the spring into the rim. I did it alone, but it might help to have someone else hold the starting end in place. While it took a few tries, it didn’t take more than 5 minutes. Might have just gotten lucky.

  8. Hi, thanks for the great write-up. I’m attempting to convert a vintage Simplex slave clock to battery operated. But I’m stuck at removing the motor at the back of the clock. By the look of your photo (Original IBM clock movement (rear view)), my clock has the same kind of motor. The four corners of the motor seemed to be crimped down tight, how do you remove these? Thanks in advance!

    1. The “pins” are small brass rivets which I worked up and out using a small screw driver. If you look at the photo with the quartz movement, you’ll see some keyhole slots which is where those brass rivets sit. I’m guessing if you removed the two rivets on either side, you could slide the movement in the direction of the removed rivets and the head of the remaining rivets would clear the slot of the keyhole and come out.

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