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Introduction

Ever been at a garage/boot/stoop/yard sale, flea market, or junk shop and seen a weird thing that looks like a cash register and a typewriter mated? These are electromechanical calculators which our dads and granddads used in the office because electronic calculators were far off in the future.

There are many of these now on eBay, but many of them are less than functional. The last time they were used was probably in the 1960s, and all the grease has probably congealed and picked up dust and twigs and things. Also, decades of being moved around and not being serviced means that parts go out of alignment or get broken by the well-meaning and the inquisitive.

Worse, the manuals and repair guides for these machines are either rare or nonexistent. My dad tells me that a man came round the office every month to maintain the calculators. It's likely that any repair information stayed inside the company.

And so, this disassembly guide will help you take this calculator to pieces so that the pieces can be cleaned, repaired, or replaced. And hopefully you'll learn a bit about the mechanisms that make these machines go.

The specific calculator we're going to be taking apart is the Monroe KA. The KA is of the K series of Monroe calculators produced from 1921 to 1928, with the A meaning Automatic, that is, with an electric motor attached. This model came with various sizes of accumulator and counter, and can multiply and divide (manually) by successive addition and subtraction.

  1. Prepare your workspace. Cover it with clean white paper or a white mat board. Light the area more than you think you'll need, and preferably from multiple directions.
    • Prepare your workspace. Cover it with clean white paper or a white mat board. Light the area more than you think you'll need, and preferably from multiple directions.

    • Ready a cardboard box and lots of press-to-close bags to store the parts you pull off. Keep associated parts in their own bag, label each bag, and don't skimp on the number of bags!

    • Remove cats, small children, and capybaras from workspace. They like small parts, and you will be generating a lot of them.

  2. Let's first remove the carriage, which is the top part with all the number wheels on them. Position the calculator so that its keyboard faces you. This orientation defines the left and right sides of the calculator.
    • Let's first remove the carriage, which is the top part with all the number wheels on them.

    • Position the calculator so that its keyboard faces you. This orientation defines the left and right sides of the calculator.

    • Unscrew the lower left screw on the left side of the carriage.

    • If it just keeps turning, you may need to insert a screwdriver on the other end of the shaft that this screw is connected to, the one on the lower right of the right side of the carriage. Don't turn it! Just turn the left side.

  3. Put that screw in a bag immediately!
    • Put that screw in a bag immediately!

    • Label the bag as bag number 1. We'll find the serial number of the calculator shortly.

    • Pat yourself on the back. You are now officially organized.

    • In the 1920's, screw threads were standardized just as they are today. The one you just unscrewed is a #8-36.

    • All the screws are machine screws, using fine threads, and are slotted. Phillips head screws had not yet been invented!

    • The heads of the 1920's screws are basically cylinders. Today, the equivalent would be called a pan-head screw.

    • I'm not sure the lengths were standardized. If they were, I'm not too impressed with their accuracy. This one is 0.298 inches long (the threaded length), which is 19/64 inches. Yeah, they don't make screws in those sizes. If you want a replacement, go with the closest length.

  4. Pull back on these carriage latches and pivot the carriage up. This shaft runs the length of the carriage. Push it out to the right. You'll probably have to pivot the carriage up and down to help it come out. Ninety years of exposure to air can't have been good for it. Now lift the carriage completely off.
    • Pull back on these carriage latches and pivot the carriage up.

    • This shaft runs the length of the carriage. Push it out to the right. You'll probably have to pivot the carriage up and down to help it come out. Ninety years of exposure to air can't have been good for it.

    • Now lift the carriage completely off.

    • This other part comes off with it.

  5. The underside of the carriage, and the other part. The shaft is not shown. Put all of these into a box so they don't disappear.
    • The underside of the carriage, and the other part. The shaft is not shown. Put all of these into a box so they don't disappear.

  6. Remove these two screws. They are #6-40, about 3/8". On the back, remove these two screws. They are also #6-40, but about 1/4". On the front, remove these two screws. They are also #6-40, 1/4".
    • Remove these two screws. They are #6-40, about 3/8".

    • On the back, remove these two screws. They are also #6-40, but about 1/4".

    • On the front, remove these two screws. They are also #6-40, 1/4".

    • Bag all these screws in bag #1.

  7. Now just pull the right side panel off. Look at those insides!
    • Now just pull the right side panel off.

    • Look at those insides!

    • OMG it's dirty and dusty in there. Wow, yuck.

  8. Remove these two screws. They are #6-40, 1/4". They go into bag #1.
    • Remove these two screws. They are #6-40, 1/4".

    • They go into bag #1.

  9. Scratched into the back panel you'll find the serial number. Mine is 143032. Write yours on every parts bag and on the box you're using to store the bigger parts.
    • Scratched into the back panel you'll find the serial number. Mine is 143032. Write yours on every parts bag and on the box you're using to store the bigger parts.

  10. In order to remove the front panel, you'll need to remove the carriage shift handle. However, this will likely have rusted in place.
    • In order to remove the front panel, you'll need to remove the carriage shift handle. However, this will likely have rusted in place.

    • Liberally apply lubricating penetrant to the screw, the hole on the opposite side, and the joining line.

    • Don't attempt to remove the handle! We'll remove it much later on, and it can stay on while we work on the rest of the machine.

  11. Remove this one #6-40 3/8" screw. Put it in bag #1. Lift upwards and off.
    • Remove this one #6-40 3/8" screw. Put it in bag #1.

    • Lift upwards and off.

  12. True story. When I was around eight years old, my dad brought home a surplus calculator like this one. I opened up this side first, and was confronted with this view of apparently infinite complexity.
    • True story. When I was around eight years old, my dad brought home a surplus calculator like this one. I opened up this side first, and was confronted with this view of apparently infinite complexity.

    • I jiggled the controls a bit, tried to figure it out for about an hour, and when I couldn't make heads or tails of it, I took a hammer to the thing.

    • Don't do that.

    • In part, this teardown is an apology for that moment of violence. It was the 70s. I'm sure disco must be partially to blame.

  13. Tilt the calculator onto its right side so that the motor sticks straight up. Remove these two bolts, placing them in bag 1. Tilt the calculator back down.
    • Tilt the calculator onto its right side so that the motor sticks straight up.

    • Remove these two bolts, placing them in bag 1.

    • Tilt the calculator back down.

    • Pull off the motor, and unplug the wire connecting it to the calculator.

    • Set it aside.

  14. 1x machine screw, #4-48, 1/4", miniature head (1/8" dia)
    • 1x machine screw, #4-48, 1/4", miniature head (1/8" dia)

    • 8x machine screw, #6-40, 1/4"

    • 3x machine screw, #6-40, 3/8"

    • 1x machine screw, #8-36, 5/16"

    • 2x hex head bolt, 5/16-18, 7/8"

    • 2x split lock washer, 5/16"

  15. Start a new bag 2.
    • Start a new bag 2.

    • Pull straight up the 80 numeric keys, the zero key, the repeat and the nonrepeat keys. Most should come off by hand, but you will have to use pliers to pull up the stubborn ones. Put the jaws under the keys and lever them up. Use a rag to protect the calculator from the jaws.

    • Put all the keys in bag #2.

  16. Remove the screws holding the add and subtract keys. They are #4-48, 3/16".
    • Remove the screws holding the add and subtract keys. They are #4-48, 3/16".

    • Pull the add and subtract keys off.

    • Place the add and subtract keys into bag 2.

    • Start a new bag 3 and put the screws in it.

  17. 80x numeric keys
    • 80x numeric keys

    • 1x zeroing key

    • 1x repeat (R) key

    • 1x nonrepeat (blank) key

    • 1x add key

    • 1x subtract key

  18. Remove the indicated six screws. They are #5-44, 1/4". Place the screws in bag 3.
    • Remove the indicated six screws. They are #5-44, 1/4".

    • Place the screws in bag 3.

    • Lift off the whole assembly of decimal indicators and set them aside.

    • They appear to have been painted white on one side and green on the other. But who can tell under all that dirt.

  19. Remove these other six screws. They are also #5-44, 1/4". Place the screws in bag 3. Lever up the top panel, pulling on one side, then the other, until the whole thing comes off. It will come off with the front panel. Set the top/front panels aside.
    • Remove these other six screws. They are also #5-44, 1/4". Place the screws in bag 3.

    • Lever up the top panel, pulling on one side, then the other, until the whole thing comes off. It will come off with the front panel.

    • Set the top/front panels aside.

    • It's impossible to tell from the rusty top, but the top was originally painted a dark green.

  20. This would be a good time to go for a stretch.
    • This would be a good time to go for a stretch.

    • Maybe make friends with a toad.

  21. On the right side, remove this screw in the front (#8-36, 5/8"), and the screw that looks like a shaft in the middle. These screws may have split washers on them. I suspect they were all supposed to have one, but only half of the screws in this step had them.
    • On the right side, remove this screw in the front (#8-36, 5/8"), and the screw that looks like a shaft in the middle.

    • These screws may have split washers on them. I suspect they were all supposed to have one, but only half of the screws in this step had them.

    • That shaft-like screw is essentially a #8-36, 5/8" screw attached to a 1" head, 7/32" in diameter.

    • On the left side, remove this screw in the front (#8-36, 5/8") and the screw that looks like a shaft in the middle. This one is also #8-36, 5/8" but with a 1-1/2" x 7/32" head.

    • All these go into bag 3.

  22. Pull straight up using the front and rear bars, and with a little persuasion the entire keyboard module should come out. Set this entire assembly aside. Set this entire assembly aside.
    • Pull straight up using the front and rear bars, and with a little persuasion the entire keyboard module should come out.

    • Set this entire assembly aside.

  23. On the right side front, unscrew this #8-36, 1" screw and remove the washer. Place them in bag 3.
    • On the right side front, unscrew this #8-36, 1" screw and remove the washer.

    • Place them in bag 3.

    • Remove the switch and wire and set it aside.

    • On the left side front, remove the corresponding screw, #8-36, 5/8".

    • Put it in bag 3.

  24. 12x machine screw, #5-44, 1/4"
    • 12x machine screw, #5-44, 1/4"

    • 2x machine screw, #4-48, 3/16"

    • 3x machine screw, #8-36, 5/8"

    • 1x machine screw, #8-36, 1"

    • 3x split lock washer, #8

    • 1x flat washer, #8

    • (continued)

  25. 1x shaft with threaded end, 7/32" dia, 1 5/8" overall length, 1" travel length, #8-36
    • 1x shaft with threaded end, 7/32" dia, 1 5/8" overall length, 1" travel length, #8-36

    • 1x shaft with threaded end, 7/32" dia, 2 1/8" overall length, 1 17/32" travel length, #8-36

  26. Start a new bag 4. Remove the retaining clip. Rotate the clip so that the gap is facing up. Now hook your needlenose pliers into the ears and pull down slowly but firmly. Hopefully the clip will remain on the jaws of the pliers, but it may decide to escape. In that case, go find it. Remove the washer.
    • Start a new bag 4.

    • Remove the retaining clip. Rotate the clip so that the gap is facing up. Now hook your needlenose pliers into the ears and pull down slowly but firmly. Hopefully the clip will remain on the jaws of the pliers, but it may decide to escape. In that case, go find it.

    • Remove the washer.

    • Remove the middle gear.

    • Place all these into bag 4.

  27. With your finger, pull the cover plug release lever towards the front of the calculator. Still holding the lever, pull the cover plug off its shaft. Place the cover plug in bag 4.
    • With your finger, pull the cover plug release lever towards the front of the calculator.

    • Still holding the lever, pull the cover plug off its shaft.

    • Place the cover plug in bag 4.

    • In case of no electricity, the cover plug would be removed and a crank would be inserted. I have never found any of these machines still having the crank.

  28. Gear, 77t, with two timing markers
    • Gear, 77t, with two timing markers

    • Flat washer, 1/2" od, 5/16" id

    • Retaining clip, 0.040" wire

    • Cover plug

  29. Start a new bag 5. In the same way you removed the middle gear, remove the retaining clip and washer from the crank gear.
    • Start a new bag 5.

    • In the same way you removed the middle gear, remove the retaining clip and washer from the crank gear.

    • Place clip, washer, and gear in bag 5.

  30. Gear, 77t, with one timing marker
    • Gear, 77t, with one timing marker

    • Washer, 5/8" od, 7/16" id

    • Retaining clip, 0.040" wire

  31. Start a new bag 6. On the right side front of the machine, unhook the repeat/nonrepeat detent spring on both sides. Unscrew this screw, #8-36, 5/16" with a 0.1" long, 7/32" diameter shoulder.
    • Start a new bag 6.

    • On the right side front of the machine, unhook the repeat/nonrepeat detent spring on both sides.

    • Unscrew this screw, #8-36, 5/16" with a 0.1" long, 7/32" diameter shoulder.

    • Remove the latch lever, and put it with spring and screw in bag 6.

    • Unscrew this screw, #8-36, 5/16" and put it in bag 6.

    • Pull off the zero/repeat/nonrepeat key assembly. Put it in bag 6.

    • This assembly can be seen in the 1920 patent US1432616.

  32. 1x machine screw, #8-36, 5/16"
    • 1x machine screw, #8-36, 5/16"

    • 1x machine screw, #8-36, 5/16" with 0.1", 7/32" diameter shoulder

    • 1x expansion spring, 0.020" wire, 3/16" od, 13/16" length

    • Repeat/nonrepeat/zero assembly (2 parts)

    • Latch lever

  33. Start a new bag 7. On the left side rear of the machine, unhook the top two springs from the indicated post. Unscrew this screw. There is a nut on the other side of the frame, so be sure to catch it.
    • Start a new bag 7.

    • On the left side rear of the machine, unhook the top two springs from the indicated post.

    • Unscrew this screw. There is a nut on the other side of the frame, so be sure to catch it.

    • Remove the bell mechanism. Place all parts in bag 7.

  34. Remove this part as well, and put it in bag 7. Unscrew the bell. It is a #6-40, 1/4" screw.
    • Remove this part as well, and put it in bag 7.

    • Unscrew the bell. It is a #6-40, 1/4" screw.

    • Place bell and screw in bag 7.

  35. On the left side, we will be removing this lever. It is held on its shaft with a retaining clip and a washer. The clip is actually just what appears to be one loop of a thick spring. Find the gap in the wire, then use the dental pick and a very small screwdriver to pry apart the gap enough so that you can remove it with the needlenose pliers. Don't worry about bending or breaking this thing. I think in the rebuild we'll replace these with retaining rings.
    • On the left side, we will be removing this lever.

    • It is held on its shaft with a retaining clip and a washer. The clip is actually just what appears to be one loop of a thick spring. Find the gap in the wire, then use the dental pick and a very small screwdriver to pry apart the gap enough so that you can remove it with the needlenose pliers.

    • Don't worry about bending or breaking this thing. I think in the rebuild we'll replace these with retaining rings.

    • Retaining rings hadn't been invented by the time these calculators were built. The Seeger retaining ring was invented in Germany around 1927 by Hugo Heiermann.

    • Remove the washer (5/16" outer diameter).

    • Also unhook the end of the spring from its post.

    • Place retaining clip, washer, and lever into bag 7.

  36. Unhook this spring at the indicated point. As with the previous lever, remove the retaining wire and washer (1/2" outer diameter) along with the lever.
    • Unhook this spring at the indicated point.

    • As with the previous lever, remove the retaining wire and washer (1/2" outer diameter) along with the lever.

    • Put everything in bag 7.

  37. Start a new bag 8. As before, remove retaining wire, washer, and lever. The washer is 5/16" o.d.
    • Start a new bag 8.

    • As before, remove retaining wire, washer, and lever. The washer is 5/16" o.d.

    • Put these parts in bag 8.

  38. Again, remove retaining wire, washer (1/2" o.d.) and lever. Place in bag 8.
    • Again, remove retaining wire, washer (1/2" o.d.) and lever.

    • Place in bag 8.

  39. Tip the calculator onto its right side and unscrew four of the five feet from the bottom.
    • Tip the calculator onto its right side and unscrew four of the five feet from the bottom.

    • You may not have to use a screwdriver. I could just turn the feet and they unscrewed.

    • Place the feet in bag 8.

  40. Just pull it right off and set it aside. The bottom mat may stick to the frame. Just pull on it until it comes off. Flip the calculator so it is upside down.
    • Just pull it right off and set it aside. The bottom mat may stick to the frame. Just pull on it until it comes off.

    • Flip the calculator so it is upside down.

  41. Start a new bag 9. On the left side (which is now on the right, since you've flipped the thing over, but we'll still call it the left side) unscrew the set screw, #6-40, 3/16", from the collar.
    • Start a new bag 9.

    • On the left side (which is now on the right, since you've flipped the thing over, but we'll still call it the left side) unscrew the set screw, #6-40, 3/16", from the collar.

    • I would unscrew it completely. Put it in bag 9.

    • Rotate the collar and move it down the shaft a bit. This is to loosen it. You probably won't have to use penetrating lubricant or lubricating penetrant.

  42. Flip the calculator back right side up. On the left side, remove this screw. It is 3/16-32, 1", 1/4" diameter shoulder. Put it in bag 9.
    • Flip the calculator back right side up.

    • On the left side, remove this screw. It is 3/16-32, 1", 1/4" diameter shoulder. Put it in bag 9.

    • On mine, the spring is broken. Not sure where it was supposed to attach.

    • Remove the lever. You may have to maneuver it a bit to get it free. Put it in bag 9.

  43. On the inside part of the left frame, unhook this end of the large spring. Back on the outer side of the left frame, bend this cotter pin and pull it out of its hole. Put it in bag 9. Don't worry if it breaks, because it is easily replaced. Pull the entire lever assembly with shaft straight out. Pull it smoothly along the direction of the shaft, possibly using another hand to push the shaft collar off the other end.
    • On the inside part of the left frame, unhook this end of the large spring.

    • Back on the outer side of the left frame, bend this cotter pin and pull it out of its hole. Put it in bag 9. Don't worry if it breaks, because it is easily replaced.

    • Pull the entire lever assembly with shaft straight out. Pull it smoothly along the direction of the shaft, possibly using another hand to push the shaft collar off the other end.

    • Put the collar in bag 9, and set the lever/shaft assembly aside.

  44. On the left side, remove this screw, #8-36, 3/4", 7/32" shoulder. There is a washer, 7/16" o.d., between the lever and the frame. Make sure you catch it.
    • On the left side, remove this screw, #8-36, 3/4", 7/32" shoulder.

    • There is a washer, 7/16" o.d., between the lever and the frame. Make sure you catch it.

    • Remove the lever. Put all parts in bag 9.

  45. Unhook the spring from its post. Remove the screw, #8-36, 3/8", 7/32" shoulder.
    • Unhook the spring from its post.

    • Remove the screw, #8-36, 3/8", 7/32" shoulder.

    • Remove lever and place it with screw in bag 9.

  46. You deserve it.
    • You deserve it.

  47. Remove these two screws, #4-48, 1/4" and put them in bag 9. Remove the retaining bar.
    • Remove these two screws, #4-48, 1/4" and put them in bag 9.

    • Remove the retaining bar.

    • Get a few paper towels, because the rock bars will be very greasy.

    • Remove the rock bars, wrapping them in the paper towels. We can clean them later.

    • Also put the retaining bar in with them.

  48. Start a new bag 10. The oiling tube leads down to a hole in a collar. On the left side rear, remove this screw and put it in bag 10.
    • Start a new bag 10.

    • The oiling tube leads down to a hole in a collar.

    • On the left side rear, remove this screw and put it in bag 10.

    • Put the oiling tube into bag 10.

    • Remove this 3/8" nut and put it into bag 10.

  49. This could probably have been seen from the bottom if we had taken it off first.
    • This could probably have been seen from the bottom if we had taken it off first.

    • The model number on this one is KA-163, which indicates a 16 digit accumulator and 3 registers (the accumulator plus two counters).

    • The rest is the serial number.

  50. Unscrew the 3/8" hex standoff from the threaded shaft. You may need to use wrenches to prevent the shaft from rotating, but probably not.
    • Unscrew the 3/8" hex standoff from the threaded shaft.

    • You may need to use wrenches to prevent the shaft from rotating, but probably not.

    • Place the standoff in bag 10.

  51. Pull the motor mount away from the frame. You may have to wiggle it and gently pry it off. Set it aside. Remove the three 36t/12t gears by just sliding them out. Put them in bag 10.
    • Pull the motor mount away from the frame. You may have to wiggle it and gently pry it off.

    • Set it aside.

    • Remove the three 36t/12t gears by just sliding them out. Put them in bag 10.

  52. On the right side rear, remove these two screws. Put the screws in bag 10. Unhook the spring from its lever and put the spring with part into bag 10.
    • On the right side rear, remove these two screws.

    • Put the screws in bag 10.

    • Unhook the spring from its lever and put the spring with part into bag 10.

    • Remove the axle half-bushing and put it in bag 10.

  53. On the left side rear, remove these two screws.
    • On the left side rear, remove these two screws.

    • Remove the half-bushing. Note that it has a larger arc and it has a hole in it where the oil from the oiling tube drips in.

    • Place screws and half-bushing into bag 10.

  54. With just a little persuasion, pull off the entire carry/drive shaft assembly. The motor drive gear should slide off.
    • With just a little persuasion, pull off the entire carry/drive shaft assembly.

    • The motor drive gear should slide off.

    • Set these assemblies aside.

  55. On the right side rear, remove this screw, 3/16-32, threaded length 1/2", and the spring at the indicated point. There is nut on the other side, so it will be helpful to use a wrench to hold the nut. The screw on mine doesn't come off the lever. There is a large bushing between the lever and the frame which does not come off, either.
    • On the right side rear, remove this screw, 3/16-32, threaded length 1/2", and the spring at the indicated point. There is nut on the other side, so it will be helpful to use a wrench to hold the nut.

    • The screw on mine doesn't come off the lever. There is a large bushing between the lever and the frame which does not come off, either.

    • Place in bag 10.

  56. Remove screw, 3/16-32, threaded length 13/32". As before, there is a nut on the other side. There is also a washer, 3/8" od, 0.047" thickness, between the lever and the frame.
    • Remove screw, 3/16-32, threaded length 13/32". As before, there is a nut on the other side.

    • There is also a washer, 3/8" od, 0.047" thickness, between the lever and the frame.

    • The screw has an eccentric shoulder on it.

    • Place all parts in bag 10.

  57. Remove two screws, #8-36, 10/32" and 3/16-32, threaded length 7/16". Remove lever assembly.
    • Remove two screws, #8-36, 10/32" and 3/16-32, threaded length 7/16".

    • Remove lever assembly.

    • Place all parts in bag 10.

  58. What's in bag 10?
    • What's in bag 10?

  59. Start a new bag 11. From now on, we'll assume that all parts you pull off, as long as they are small enough, go into the current bag.
    • Start a new bag 11.

    • From now on, we'll assume that all parts you pull off, as long as they are small enough, go into the current bag.

    • From right side rear, remove 5/16" hex nut, #6-40, 0.095" thick.

    • On the inside of the right side rear, remove 5/16" hex nut, 0.156 thick, and screw, #6-40, 1/4".

    • Remove the lever that the screw was holding in.

  60. Pull the clutch assembly away from the frame, then rotate down, and pull off. Remove this gear. It will just slide off.
    • Pull the clutch assembly away from the frame, then rotate down, and pull off.

    • Remove this gear. It will just slide off.

  61. All these pieces slide off. Watch out for this tiny little key! It keeps the clutch parts aligned as they slide back and forth.
    • All these pieces slide off.

    • Watch out for this tiny little key! It keeps the clutch parts aligned as they slide back and forth.

  62. What's in bag 11?
    • What's in bag 11?

  63. Start a new bag 12.
    • Start a new bag 12.

    • On the inside right rear, remove this screw, #8-36, 1/2", and the eccentric nut.

  64. On the right side rear, remove these three screws, #8-36, 5/16". The middle screw holds down a part which has a hook for a spring. Unhook the spring from the hook. Pull the lever back and manipulate the loose part that you just unscrewed from the third screw to remove it.
    • On the right side rear, remove these three screws, #8-36, 5/16".

    • The middle screw holds down a part which has a hook for a spring. Unhook the spring from the hook.

    • Pull the lever back and manipulate the loose part that you just unscrewed from the third screw to remove it.

  65. On the left rear, remove these three screws, #8-36, 5/16". The screw on the right is difficult to get to. Use a long thin screwdriver to loosen the screw a tiny bit, then a smaller screwdriver to remove the screw. The screw on the right holds down two parts.
    • On the left rear, remove these three screws, #8-36, 5/16".

    • The screw on the right is difficult to get to. Use a long thin screwdriver to loosen the screw a tiny bit, then a smaller screwdriver to remove the screw.

    • The screw on the right holds down two parts.

    • The screw on the left has a hook for a spring which runs along the length of the machine. You will likely be able to remove a short segment of the larger surrounding spring. Hook the end of the interior spring around the bushing after removing the short outer spring segment.

  66. On the left side rear, remove this screw, #8-36. Remove this screw, #8-36 with 1/4" shaft. Slide the gear off. Note that this gear has a recess for the screw.
    • On the left side rear, remove this screw, #8-36.

    • Remove this screw, #8-36 with 1/4" shaft.

    • Slide the gear off. Note that this gear has a recess for the screw.

    • Slide another gear off the right side. This gear does not have a recess. Note: I might have gotten this gear from a few steps farther down, need to verify this.

  67. On the right side rear, remove this hex nut, 5/16" x 0.095". Remove from the inside the corresponding screw with shaft.
    • On the right side rear, remove this hex nut, 5/16" x 0.095". Remove from the inside the corresponding screw with shaft.

    • From the inside, knock out this screw, 3/16-32.

    • Now remove the clutch support that you just freed from the screws.

  68. What's in bag 12?
    • What's in bag 12?

  69. Start a new bag 13. On the left rear side, remove this screw, 3/16-32, 7/16", holding two levers.
    • Start a new bag 13.

    • On the left rear side, remove this screw, 3/16-32, 7/16", holding two levers.

    • Unhook the lever springs. Note that the lever with the shorter arm and shorter spring goes in front.

    • There is also a washer between the screw head and the first lever, 9/32" od, 7/64" thick.

  70. Remove this screw, 3/16-32, 1/2".
    • Remove this screw, 3/16-32, 1/2".

    • Remove the lever and the bushing between the lever and the frame.

  71. Remove this screw, #8-36, 1/2", along with its plate and the washer, 5/16" od, 1/8" thick, that is between the plate and the frame.
    • Remove this screw, #8-36, 1/2", along with its plate and the washer, 5/16" od, 1/8" thick, that is between the plate and the frame.

  72. Remove the driver wheel assembly. Pry up the two axles gently from their four semi-circular seats and set aside.
    • Remove the driver wheel assembly. Pry up the two axles gently from their four semi-circular seats and set aside.

  73. Remove this screw, #8-36, 1/2", with eccentric nut. Remove the levers on both right and left side. Note that the tabs on the tops of the levers both face to the left, and that the lever from the left side has its middle tab bent inwards.
    • Remove this screw, #8-36, 1/2", with eccentric nut.

    • Remove the levers on both right and left side. Note that the tabs on the tops of the levers both face to the left, and that the lever from the left side has its middle tab bent inwards.

  74. What's in bag 13?
    • What's in bag 13?

  75. Start a new bag 14. On right side and left side rear, remove four screws, #8-36, 5/16". Remove the semicircular half-bushings.
    • Start a new bag 14.

    • On right side and left side rear, remove four screws, #8-36, 5/16".

    • Remove the semicircular half-bushings.

    • Pry up and out the selecting gear assembly. There are two clips holding the axle, just pull.

    • Set the selecting gear assembly aside.

  76. On the inside left, remove the screw, #8-36. There is a hex nut, 5/16" x 5/32", on the other side of the frame. Remove clip and lever.
    • On the inside left, remove the screw, #8-36. There is a hex nut, 5/16" x 5/32", on the other side of the frame.

    • Remove clip and lever.

    • Note the order: screw, clip, lever, frame, nut.

  77. On the right inside, remove this screw, #8-36. There is a hex nut, 3/16" x 5/32", on the other side of the frame. Remove lever and clip.
    • On the right inside, remove this screw, #8-36. There is a hex nut, 3/16" x 5/32", on the other side of the frame.

    • Remove lever and clip.

    • Note the order, which is different from the left side: screw, lever, clip, frame, nut.

  78. What's in bag 14?
    • What's in bag 14?

  79. Start a new bag 15.
    • Start a new bag 15.

    • On the right side, remove this screw, 3/16-32 x 5/8".

  80. On the left side, remove this screw, 3/16-32 x 5/8" and split washer, 5/16" od x 0.085".
    • On the left side, remove this screw, 3/16-32 x 5/8" and split washer, 5/16" od x 0.085".

  81. On the left side, unhook this spring from its post on the frame. Leave the other end on the part. This other spring is on two posts, remove it completely. It is 3/16" in diameter, with a wire size of 0.012".
    • On the left side, unhook this spring from its post on the frame. Leave the other end on the part.

    • This other spring is on two posts, remove it completely. It is 3/16" in diameter, with a wire size of 0.012".

    • On the right side rear, unscrew this hex spacer. It has a #8-36 thread.

  82. What's in bag 15?
    • What's in bag 15?

  83. The only thing now preventing the two frames from being separated is this gear. It is fixed to the shaft with a taper pin.
    • The only thing now preventing the two frames from being separated is this gear.

    • It is fixed to the shaft with a taper pin.

    • A taper pin is a pin that tapers from a wide end to a narrow end used to affix parts onto a shaft. The machinist would put the gear on the shaft, drill a hole, then taper the hole by using a tapering reamer. Then the machinist would put the taper pin in, give it a few gentle whacks with a hammer, and grind off any end sticking out too much.

    • Taper pins were better than set screws because a taper pin leaves no possibility for the parts to rotate.

    • They're also a pain to remove after 90 years.

  84. Before you get started on removing the taper pins, you must go for a luxurious stretch.
    • Before you get started on removing the taper pins, you must go for a luxurious stretch.

  85. Do this outside, or in a well-ventilated area. Take a heat gun and blow heat on the part for about two minutes to get it up to maximum temperature.
    • Do this outside, or in a well-ventilated area.

    • Take a heat gun and blow heat on the part for about two minutes to get it up to maximum temperature.

    • Spray the part with penetrating lubricant. It will smoke slightly, and it won't ignite.

    • If the lubricant evaporates, spray some more on, until the lubricant shows no sign of evaporating anymore, meaning that the temperature of the part has dropped significantly.

    • Repeat the heat - lubricant cycle three more times.

    • The idea is to break the bond between the taper pin and the part, and get some lubricant in the tiny microscopic gap in between.

  86. Take the part over to the arbor press.
    • Take the part over to the arbor press.

    • You must support the part against something that will provide maximum surface area to the part, but also allow the taper pin to move at the bottom.

    • A piece of aluminum with a semicircular depression is perfect. You can do this either with a drill, then sawing off halfway through the diameter of the hole, or with an endmill of the right diameter.

    • Then cut a smaller notch the length of the depression to allow the pin to move. Again, this could be done with a drill and a saw, or an endmill.

  87. With calipers, measure the width of each end of the pin. You want to find the smaller of the two ends. The smaller the pin, the more difficult this is.
    • With calipers, measure the width of each end of the pin. You want to find the smaller of the two ends. The smaller the pin, the more difficult this is.

    • On my machine, the smaller pins had one end ground flush to the part, and the other sticking out. The end that stuck out was the smaller end.

    • Many of the larger taper pins have a rounded end and a flat end. The rounded end is the larger end.

    • Position the part in the arbor press so that the part is supported by the jig you made, and the small end of the pin is up.

    • Press on the pin with the arbor press. If you are close to using all of your strength and the pin has still not moved, give it a few more heat - lubricant cycles.

    • If the thing still doesn't move, you may be pressing on the wrong end. In which case, see the next step.

  88. If you tried to press the pin out, and it just won't come out, or maybe the pin is actually ground flush on both ends so there's nothing to press, then you will have to get a 1/16" end mill (not a drill) and drill out a bit of each end.
    • If you tried to press the pin out, and it just won't come out, or maybe the pin is actually ground flush on both ends so there's nothing to press, then you will have to get a 1/16" end mill (not a drill) and drill out a bit of each end.

    • Give it a few cycles of heat - lubricant.

    • Then use a 1/16" flat pin punch and hammer at the pin. But don't use your full strength: that will just compress the pin and expand it, making it more stuck.

    • If that still doesn't work, you'll have to drill out the entire pin, which is unfortunate because now you will have to replace the pin when you assemble the machine.

  89. Now, assuming that the arbor press did move the pin, you can gently knock the pin out with a 1/16" flat pin punch and a hammer. Now, assuming that the arbor press did move the pin, you can gently knock the pin out with a 1/16" flat pin punch and a hammer. Now, assuming that the arbor press did move the pin, you can gently knock the pin out with a 1/16" flat pin punch and a hammer.
    • Now, assuming that the arbor press did move the pin, you can gently knock the pin out with a 1/16" flat pin punch and a hammer.

  90. Start a new bag 16. Remove the taper pin from the gear on the upper left side. Bag the taper pin. It should be about 0.086" on the wide end, 0.071" on the narrow end, and about 0.410" long. That is a taper of about 1/2" per 12", which is not a modern standard taper pin size -- 1/4" per 12" is the standard today. However, If the wide end were 0.080" then we'd get a standard taper. Perhaps the wide end was widened a bit by the installation?
    • Start a new bag 16. Remove the taper pin from the gear on the upper left side.

    • Bag the taper pin. It should be about 0.086" on the wide end, 0.071" on the narrow end, and about 0.410" long. That is a taper of about 1/2" per 12", which is not a modern standard taper pin size -- 1/4" per 12" is the standard today.

    • However, If the wide end were 0.080" then we'd get a standard taper. Perhaps the wide end was widened a bit by the installation?

    • Now you can pull apart the frame. The gear will slide off its shaft. You may have to pry off the big iron piece in the middle, and move one side of the frame, then the other, but eventually the sides will separate.

    • In the picture, the second shaft from the right, the one with the spring, will also come off. Make sure the spring doesn't roll away!

    • You can pull of the rightmost rectangular part and the shaft second from the right. Set the rectangular part aside, and bag the spring.

  91. You can also remove and set aside the shaft with threaded ends all the way on the left. Now the left frame is free. Set it aside.
    • You can also remove and set aside the shaft with threaded ends all the way on the left.

    • Now the left frame is free. Set it aside.

  92. From the right frame, carefully pry off the iron crosspiece. Set it aside.
    • From the right frame, carefully pry off the iron crosspiece. Set it aside.

  93. On the right frame, unscrew this screw. There is a thin nut on the other side of the frame that you should try to hold steady or loosen slightly. If that doesn't work, just slowly turn the screw, since the nut will add lots and lots of friction.
    • On the right frame, unscrew this screw. There is a thin nut on the other side of the frame that you should try to hold steady or loosen slightly. If that doesn't work, just slowly turn the screw, since the nut will add lots and lots of friction.

    • Remove the spring from its post on the frame, and remove the lever.

    • The nut should now slide out.

  94. What's in bag 16?
    • What's in bag 16?

  95. Start a new bag 17. Remove the inner taper pin and gear from the shaft at the back.
    • Start a new bag 17.

    • Remove the inner taper pin and gear from the shaft at the back.

    • Slide the shaft out of the right frame.

    • Remove the remaining taper pin and gear from the shaft.

    • Set the shaft aside.

  96. Loosen, but do not remove, this set screw. Slide the ring over a bit. On the right frame, there is a cam ring that is loose. Remove it, if you haven't already. You should now be able to jiggle these levers loose, Remove their springs first. You will probably have to slide the shaft a bit out, also.
    • Loosen, but do not remove, this set screw. Slide the ring over a bit.

    • On the right frame, there is a cam ring that is loose. Remove it, if you haven't already.

    • You should now be able to jiggle these levers loose, Remove their springs first. You will probably have to slide the shaft a bit out, also.

  97. Remove this #8-36, 3/8" screw. It has a flat head, which (for some reason) means it has a triangular-profiled head. Now remove the assembly off the frame and bag it.
    • Remove this #8-36, 3/8" screw. It has a flat head, which (for some reason) means it has a triangular-profiled head.

    • Now remove the assembly off the frame and bag it.

  98. Remove taper pin and part from the right side of the shaft.
    • Remove taper pin and part from the right side of the shaft.

    • The taper pin is larger than the previous ones: 0.112" at the big end, 0.096" at the small end, and 0.517" long. This places the taper at nearly 3/8" per 12", which is not standard.

    • Again, though, if the wide end were 0.107", then the pin would be standard.

    • Slide the shaft out of the frame, and slide the bushing off the shaft.

  99. Remove taper pin and part from the other end of the shaft.
    • Remove taper pin and part from the other end of the shaft.

  100. What's in bag 17?
    • What's in bag 17?

  101. Start a new bag 18. On the front of the right frame, remove this 1" hex standoff with 3/16-32 threaded male end. There is also a washer, o.d. 0.379 x 0.048. In the middle inside of the right frame, remove this 3/8 nut. There is a split washer on the inside and a regular washer on the outside, plus a screw-in post with 3/16-32 threads.
    • Start a new bag 18.

    • On the front of the right frame, remove this 1" hex standoff with 3/16-32 threaded male end. There is also a washer, o.d. 0.379 x 0.048.

    • In the middle inside of the right frame, remove this 3/8 nut. There is a split washer on the inside and a regular washer on the outside, plus a screw-in post with 3/16-32 threads.

    • On the back of the right frame, unscrew the #8-36 screw holding the gear.

  102. On the front of the left frame, unscrew the 1.5" hex standoff with 3/16-32 threaded male end. Remove its accompanying washer. In the middle of the left frame, unscrew this #8-32 spring post, remove its accompanying washer and the part it was holding on. In the front inside of the left frame, remove this 3/8 nut and the spring post 1/4-28 screw.
    • On the front of the left frame, unscrew the 1.5" hex standoff with 3/16-32 threaded male end. Remove its accompanying washer.

    • In the middle of the left frame, unscrew this #8-32 spring post, remove its accompanying washer and the part it was holding on.

    • In the front inside of the left frame, remove this 3/8 nut and the spring post 1/4-28 screw.

  103. Remove this ordinary #6-40 screw and its nut. Remove the padded rest part.
    • Remove this ordinary #6-40 screw and its nut. Remove the padded rest part.

    • We've pulled everything we can off the frames, and have completed the disassembly of the main body.

  104. So it's a good time for a break. Maybe go on a pirate ride. Be sure you secure your iPhone.
    • So it's a good time for a break. Maybe go on a pirate ride.

    • Be sure you secure your iPhone.