The “Day” complication is a feature only found on the NH36 variation of the NH series of movements. This is an ideal replacement movement for a Seiko 7S26 or 4R36. This is a quick guide to removing and replacing the day disk which can often be called the day wheel. Day Disk Mods (NH36) will require the removal of the dial and hands. You may want swap the the day disk for the following reasons.

  • Your are changing a broken movement
  • Upgrading your movement from 7S26 – NH36
  • Case swapping to a case with a different crown position.
  • To retro fit an aftermarket day disk

Tools & Consumables

  • Movement Holder
  • Screw Driver
  • Tweezers
  • Rodico
  • Pegwood

Removing the Day Disk – Day Disk Mod NH36

The day disk/wheel is retained by a small clip. This needs to be removed to remove the day wheel. The clip is located around the pinion in the centre of the movement.

The clip is a c shape, you will need to locate the opening in the “C”. Use a red 1.20mm screwdriver, this is the ideal size. Lay it flat on the date wheel at the opening . Insert the blade of the screwdriver gently in to the opening of the clip. This blade should make its way under the clip. Once you are successfully underneath it you can carefully work your way around the pinion. The clip will reach a height where it can be removed easily with a pair of tweezers.

Movements - SKX & 5KX -  removing the of a Seiko NH36 / 7S26  -
Removing the clip.
Movements - SKX & 5KX -  removing theclip with tweezers of a Seiko NH36 / 7S26  -
Lifting the Clip away with tweezers.

The clip may twist away from you around the Pinion. This will become frustrating and you will need to perceiver here. To over come this apply a little pressure to the opening of the clip and turn the movement around 180 degrees, you may find a gap big enough to get the screwdriver blade underneath.

This clip can then be removed with a set of tweezers.

Next on the list is to remove the day wheel – this is easily done with some Rodico. Press some Rodico gently onto the date wheel and it will attach itself, You can then lift it away. This can then be stored.

Movements - SKX & 5KX -  removing the day wheel of a Seiko NH36 / 7S26 with roddico  -
Removing the day wheel/disk with Rodico.

Replacing the Day Disk

The day wheel can now be placed back on to the hour wheel. This will sit a little proud and will need to be located on to the day wheel jumper. You should be wearing gloves so you can use your fingers to do this if you wish. Turn the disk anti-clockwise and it should click into place.

Movements - SKX & 5KX -  placing the day disk/wheel a Seiko NH36 / 7S26  -
Place the date wheel on the movement.
Movements - SKX & 5KX -  twisting the day disk of a Seiko NH36 / 7S26  -
Twist the day disk anti-clockwise to lock it into the jumper.

To complete the day disk mod (NH36) , the last part is to lock the clip back into position to retain the day disk. The clip need to be placed over the pinion. Tweezers are the best tool for the job. You may need to align the clip to the centre after it has been placed with the tweezers. Once the position is satisfactory, secure the clip into the final locking position. This can be done with a pair of tweezers. Place the tweezers either side of the pinion and apply a downward pressure. There should be a satisfactory click when the clip is located.

Movements - SKX & 5KX - replacingtheclip on  a Seiko NH36 / 7S26  -
Placing the clip on to the pinion
Movements - SKX & 5KX - pressing the clip of  a Seiko NH36 / 7S26  -
Pressing the clip down
Movements - SKX & 5KX - clpse up of   a Seiko NH36 / 7S26 movement  -
With the clip in place.

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