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

35 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.
      thanks!
      Rosie

      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 norkro.com. I think the hands were $1 each.

        1. I have an old Edwards school clock I’d like to do the same with – if I read correctly the parts list is:
          1 – Takane MVT312CHT
          1 – Norkro HND 1351
          1 – Norkro HND 68024
          Is that correct?

          Also – thank you for posting this!

          1. If this is a similar sized clock, you will want to use a “high-torque quartz movement.” If it has a second hand and you want it to to be a “continuous sweep” (vs ticking) Then the Takane MVT312CHT will work, but the also sell different shaft depths which could work depending on the depth of the clock case. If you are going to modify and use the original clock hands, you just need any hour, minute, second hands that fit the movement you purchase. You will just be using the hands you buy for parts – so the actual item number doesn’t matter. When you order the movement, just tell them you need hands that fit the movement. Some kits come with hands included.

  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!

    1. This particular IBM slave clock is 13 1/2″ and has 95925 on the very top of the face above the 12.

  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.

          1. Having the same problem here.. 1. Place the spring into the rim of clock 2. Press the glass inside the spring circumference
            is this correct?

          2. You place the glass dome into the clock housing and the bezel is then inserted around the glass to hold it in.

  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.

  9. Great instructions! I’ve got the exact IBM clock that I will convert to battery per your instructions. Question; how long does the battery last?

      1. Wow, 2 years – I was not expecting it to last that long. The parts came in and I was able to convert my clock. After I took the motor off, the white clock face was not secured to the metal back so I had to secure it using double-sided tape. I also had to drill the center hole down a little on the second hand and glue the pin to it. The pin would not fit through the hole, also the hole was slightly raised on mine. Other than that, everything turned out great.

  10. It looks to be about 6 years since you converted the clock or posted this….how has your movement held up over time using the Takane High Torque Clock Movement? any failure with the movement or hands?

    1. I actually converted (3) within 6 months and they are all working flawlessly. They do seem to gain about 2 minutes per year, but that’s to be expected.

  11. I just completed the conversion of a 9″ clock – wanted a smaller one for my home office, and shopped eBay hard for one. Got a Simplex model that has for whatever reason a pretty highly yellowed plastic face. I cleaned that up a little using Windex which seemed to work well and didn’t harm the number printing on the face.

    I sanded down and repainted the case using Rustoleum silver hammertone paint, which worked pretty well. Original case was a matte-finished silver, and the hammertone looks period correct with the wrinkle-finish stock hands.

    The shaft hole for the quartz movement is FAR smaller than the opening in the steel case for the clock. I considered this for a bit, but instead of rigging up some sort of bushing to positively center it, I just got an appropriately-sized stainless washer for the front of the hole and mounted my movement (used the same one listed in the original article). This approach works fine.

    However, the length of the shaft was now too long and the hands were too far out from the face and the crystal would interfere. So instead of finding the right shaft length, it was back to the hardware store for more washers for the back of the movement this time to space it out some and shorten the length of shaft that protruded from the front, face side. This isn’t an optimal solution, and I’d encourage anyone doing this with the 9″ face clock to measure the original shaft length and see if there’s a more appropriate shaft length that comes closer to the original.

    I struggled mightily with the hands. First tip – on my clock (perhaps because of the vintage or the smaller size) the second hand unscrews directly. There’s no nut. I puzzled over this for a while. Fortunately, I didn’t screw up the second hand – that came later 🙂

    I drilled out the brass collet on the hour hand. I think anyone who does this will struggle; brass is notorious for grabbing as you drill it. I didn’t use lubrication, that probably would have helped a lot. There’s just not much depth on the collet underside to grab onto with any sort of vice, and the press/swage fit of the brass collet into the stamped metal hour hand isn’t tight enough to resist the same forces that cause the bit to grab the brass as you drill. Good luck on this one.

    I think the solution of adhering the new minute hand’s square-shanked hole onto the old hand’s back is conceptually a good one. All of the new hands trim very easily with scissors – don’t be afraid, dive right in. Be careful aligning the holes; there’s not too much extra clearance on the old hole and without care, you could block part of the new hole. I used cyanoacrylate adhesive (Krazy glue, though not that brand) and it worked very well. No need to remove the paint on old or new surface; in fact, I’d recommend keeping the paint intact as bare aluminum (at least the new hand and maybe the old one too) is notoriously hard to paint and bond.

    However, I was mightily disappointed to find that the flats machined on the minute hand shaft of the movement to mate with the newly-modified hand were too shallow to allow the thickness of the old hand with the new hand portion with flats that was adhered onto it. There wasn’t enough thread extending past the top of the hand to allow the nut to engage. I tried and struggled for a while. And I don’t think I did badly with the cyanoacrylate; it is very low viscosity stuff and forms a very thin bondline (I’d imagine would have been better for this application than epoxy). So what to do? This was the hackiest part and the part that will cause problems for anyone else and might cause me future problems. I used a Dremel with an abrasive wheel to try to add a little depth. It was sloppy, very sloppy. I couldn’t think of a good way to do it. Dremel even at low speeds was too aggressive, and a file was too slow and put what I felt like was too much force on the shaft. And I worried and still worry about all that fine brass dust that the Dremel generated that got down between the concentric shafts in the movement. Would love to hear how people solved this if they encountered it, because it’s a bad solution.

    On to the second hand – lots of problems here, too. There doesn’t appear to be any reasonable way in my example to use the stock second hand. I tried and fiddled and played and worked and ended up mangling it. No matter, I went to the movement supplier and ordered 5 or 6 new second hands (they’re cheap) that looked like they might work. There aren’t that many styles available that are long enough (and this was the 9″ clock, it would be even a smaller selection of suitable hands with the 13″ as in the article, but maybe it’s not an issue with that size). The one that looked closest to stock (and it really wasn’t a bad match) was black and had the brass center rivet/pin, so I painted it. Found a good match to the original color at a big box store, drilled a small hole in the end of a scrap of lumber, stuck the second hand pin in there and sprayed away. A caution here is that new solvent based coatings over old coatings can swell and wrinkle the old finish, and I think this is worse with thickly applied coatings, so sneak up on it with very thin coats. I wrinkled mine, but stripped it off in those places with sandpaper and recoated. Not the greatest job at the end (the sanding deformed the hand and I had to rebend it which is never the best) but it was fine.

    The biggest issue with the second hand was installation. The newly painted hand didn’t seem to engage the small pin in the movement. I tried some of the others in the assortment I ordered and some of them fit and engaged, and some of them didn’t. Disappointing after getting this far and ostensibly now having exactly the correct setup with the new hand. Anyhow, I had no idea what was going on or how to fix it. I guessed (correctly it ends up) that the hole in the pin on the hand was too large to press fit onto the pin in the movement and provide enough friction for it to work. So how to fix it? I struggled with it for a while, and used the extra second hands that I had ordered to test solutions. What ended up working is inserting a pin or needle into the pin in the second hand and using pliers to crimp the fine tubing that makes up the pin onto the needle. The needle prevents the tubing from collapsing completely, allowing you to wiggle the needle to enlarge it a bit again if you need to. This ended up working well.

    I did have to fiddle with the hands a bit, bending them slightly to allow them to clear each other as the traveled around. Also, you do need to align the hour and minute hands so that at the even hour (use 12 o’clock) the hour and minute hand are perfectly aligned at the hour mark and with each other. Because the collect in the hour hand was loosened when I was drilling it, this was easy to adjust to the correct position.

    Anyhow, thought I’d share my experiences if it helps anyone else.

  12. Just started this project. Came out of my office building when they remodeled. The building was built in 1962. The hands came off easily. It is getting the old slave gears etc off that is puzzling. Thoughts?

    1. I used Norkro Clock Company and I think they also sell on ebay. It’s important to use a high torque movement because of the size of the hands – the Takane MVT312CHT worked well for me.

  13. I have a double faced ibm slave clock. Do you have any resources for finding a replacement spring that holds the crystal in place?

    1. I have never seen a source for the replacement spring. If I was in need of one, I would look on ebay for buying a clock with broken glass or buy a complete clock and sell the glass dome (which is also hard to find).

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