Olympia SG-1 / SG-3 replica right margin stop body

thingiverse

This is a replacement for the body of a margin stop on an Olympia SG-1 or SG-3 typewriter (it may work on other models, but I only have these). The margin stop for these models was made out of an alloy of zinc, magnesium, and copper called Mazac, now known as Zamak. (You can see one on the left of the second picture). It appears that sometimes this alloy can deteriorate over time. In my case, the margin stop body and the weights in the tabulator brake expanded and crumbled away. My Olympia SG-3's margin stops were in good condition and worked fine on my SG-1, so I used the SG-3 stops as a reference when I drew the part in Fusion 360. It seemst that the bodies of the margin stops are interchangeable, though the rest of the assemblies differ slightly (the SG-1's stop as a linear gear / rack that engages with the margin rack, whereas the SG-3 has a single cross bar that does the same thing, so the SG-3s can be used on any pitch, but the SG-1's require a matching rack). This part required a bit tighter tolerances than my current printer & skill level, so I had to do a bit of carving to get the margin button to work perfectly smoothly. It is a difficult part to print as no orientation avoids the need for supports. I printed it on its back with a minimal support under the central cut. I printed this prototype in PLA for now, and it's survived a few pages of typing just fine. Luckily, the design of the SG-1 does not put much force on the margin stop: all it does is trip the bell hammer and engage the key lock; the escapement and carriage release carry merrily along past the margin (the SG-3 works this way, too). So, it will not suffer the momentum of the entire carriage slamming against it (like the left margin will). I posted about this part, and the overall restoration of this particular machine, on the [Typewriter Forum](https://typewriter.boardhost.com/viewtopic.php?id=3898)