Modifying a $230 keyboard is scary enough, but modifying two keyboards that each cost ~$230 can be downright nerve-racking if you aren’t prepared. Don’t let this scare you though, swapping the 55g domes out of a 55g Realforce and into an HHKB is a very easy procedure that only requires the most basic of tools and some patience. Throughout this guide I will try to inject as many tips and pointers as I can to ensure you have a successful transplant.
For those of you that aren’t aware of why this mod even exists the answer is simple; the glorious HHKB has never been publicly available with 55g Topre switches, a switch than many users swear by. Personally, I will always claim it to be my favorite switch without hesitation. The 55g Topre feels distinctively different than it’s popular 45g sibling, the tactile bump is crispter, and the slightly heavier actuation weight is attractive to heavy handed typist like myself.
Enough my ramblings though, let’s begin the process of making the perfect keyboard.
First you will need a few basic, yet extremely expensive supplies:
HHKB Professional 2/HHKB Type-S
Realforce U87 uniform 55g
Silencing Materials (if you want to silence either keyboard, now is the time)
Small Phillips head screwdriver
2 containers for screws
2 containers for domes/springs
Having a large, clean work space is also extremely important. The Topre springs do have a tendency to fall out when taking the rubber dome sheets off, and also tend to jump around when bumped to the slightest degree, so it’s just much safer to have a large table/work space.
I begin the procedure by disassembling the Realforce. The plastic bottom case can be easily removed by just popping the four clips on the bottom/front of the case. No screws are holding the case together. After opening the case you will need to remove the ~30 screws holding the PCB onto the top plate. These screws are an important aspect of the Topre design, as they help hold the rubber cups firmly on the PCB. I just dumped all of the screws into a small container, remembering the black screws go in the holes marked with the small white arrows and the silver screws go in the unmarked holes.
After you get all of the screws out of the Realforce, very carefully flip the PCB over, pulling it directly up a few inches before flipping it over to prevent accidentally knocking the domes off and having springs go everywhere. You should now see the small army of black 55g domes. Very carefully pull off the rubber domes (they are just held in place due to the clamping pressure that was on them between the PCB and case, there is no adheisive). Make sure to get all of the springs as well, there isn’t an easy way to get replacements! I dumped the springs/domes into a separate container, set all of the Realforce parts aside and now turn my attention to the HHKB.
To begin, open the HHKB by removing the 3 screws on the bottom/back of the keyboard. The case should slighly pop open after they are removed. Next you can unclip the cables from the controller, or if you are uncomfortable with the clip and feel like you are forcing it, simply unscrew the controller with the single screw holding it in place, and remove the bottom case.
Now you want to take out all of the small screws that sandwich the domes between the PCB and top case. After doing this, carefully flip the HHKB over in the same way as the Realforce, trying to be mindful not to accidentally knock the domes off. Once flipped you can remove all of the HHKB domes and springs and place them in a separate container. At this point you have fully disassembled both keyboards. If you were going to do a silencing mod to either this would be the time to remove the sliders and apply the silencing materials (o-rings, silencing pads, rubber sheets, etc).
Next, decide if you want to do a full 55g mod on the HHKB, or have a variable weight HHKB. Personally, I decided on the variable weight, having all of the alpha keys/number keys/space bar having 55g domes, with the modifiers having the stock 45g domes. The logic behind this is that it makes for a much more uniform swap on the Realforce end, basically allowing for the exact opposite of the HHKB. The alphas on the RF will end up being 45g and the modifiers and some of the function keys end up with 55g domes. If you do a full 55g swap on the HHKB, the Realforce ends up with a rather chaotic variable weight layout.
After deciding on what layout you want, you can begin to reassemble the keyboards, starting with the glorious HHKB. Begin by placing the top case with the sliders attached upsidedown, being held up in the corners and top edge by an object tall enough to allow the sliders to fall all the way down. I used cassettes, as they are just tall enough and I have hundreds of them around the house.
Now begin placing the black 55g Realforce domes on the HHKB, starting with the two large alpha key sheets, and filling in the edges as you go. Unless you go for an odd layout, you shouldn’t have to cut any of the existing sheets for either keyboard. Here is a picture of the layout I went with for the HHKB:
After placing the rubber sheets in place, you can begin to put the springs back into the domes. If you “lose springs” they are probably doubled up with another spring, as it can be very hard to tell when two springs are stuck on top of each other. This happened a few times while I was doing this mod, and I crawled around on my floor for half an hour looking for a spring that wasn’t lost. After getting the springs in place, gently make them as flat as possible, and check to make sure all of the rubber cups are settled perfectly in place. When you are satisfied with these parameters you can very carefully place the PCB back over the domes. This is best if the PCB is brought straight down into place, so there is no chance of a rubber dome or spring getting rattled or pushed out of place.
Now all the tricky parts are over. You simply need screw in the PCB screws that connect it to the top case, reconnect the controller (or reattach it with the single screw if you took it off) and put the top shell back together, finishing with the 3 case screws. Simply repeat the past steps with the Realforce.
Now, let your fingers bask in the glory of the perfect keyboard.
For more images see full album and more details on KeyChatter: https://www.keychatter.com/2015/07/21/how-to-moddifying-an-hhkb-with-55g-domes/. 
