This is part two of a series I am doing on modifying an IBM Model M. The key layout is discussed
here. The idea came from what Daniel Beaver did
here, this hack removes 6” to bring the total keyboard width to 15 inches or about the same as the original IBM Space Saving Keyboard.
I started with full disassemble including removing the plastic rivets (see Ripster’s Model M Rivet Replacement - Sandy's Nut Bolt Mod American Style). I found that my 4” wall razor scrapper removed the old rivets better than a chisel.
I cut up some old angle iron to make a custom miter box. I used a standard 12” hack saw with a new 32T blade to cut the plates and shell in the miter box. The steal back plate was first. I used a jig saw with metal cutting blade to notch the top right corner. The barrel plate was much quicker and easier to cut.
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I cut the bottom membrane about 5mm in from the edge of the new back plate. I cut the middle sheet slightly closer to the edge. If I were to re-do this, I would probably not cut the middle sheet at all and use it as a barrier between the back plate and top membrane. I could not cut the top membrane because traces enter and exit this area. I used a clear adhesive DHL shipping pouch to seal the traces to 5mm past the edge of the back plate and folded it under.
I drilled out the studs on the barrel plate and finished the Bolt Mod as normal. I left out the bolt beneath the Caps Lock key. That is reserved for an in-key LED mod – more on that in an upcoming article.
With the keyboard shell, I couldn’t just cut 6” off the right side; it required special cuts as I wanted to keep specific elements. For the bottom, I was able to use the miter box to make strait cuts. I used LockTite Epoxy Plastic Bonder to join the pieces. My measurements were accurate and the pieces joined perfectly. I used the razor scraper to remove the back-plate support from the cut-out section and epoxied it to the foot well.
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I did lots of planning before cutting the top of the shell. I tried to put the cuts where they would be least noticed.
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Complicating the matter was that there were no flat surfaces for clamping the piece in place while cutting. My measurements were less accurate this time and I created a .125” gap. So I cast some molds of the same spots from another shell and used these to back-fill the gap with epoxy.
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I used the razor scraper again to remove and trim the screw receiver. To glue it on the underside of the top, I mounted it using a shell screw onto the completed bottom shell, put a blob of epoxy on top, put a blob of epoxy on the completed top shell, then mounted the top shell. Allow 24 hours for the epoxy to fully cure.
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A list of things I learned from experience:
[*]I don’t like syringe type epoxy. Despite leaving it “tips up” for days, there were still large air pockets that made it difficult to dispense equal parts.
[*]When creating a cast, set the details you want to capture as the floor; air bubble rise. In the pictures where the texture is right, I used a cast.
[*]Use thin Scotch tape to mask either side of your glue joint to prevent detail from getting filled in with epoxy. In the pictures, if the joint is clean, I used tape.
[*]Take care to get the epoxy all the way to the bottom of the crack. I didn’t do a very good job on the front crack, but did much better on the back.
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