I never know what to call these things. The Brits call them “hornblock guides,” but North American engines have no hornblocks and have no need to guide them. We unimaginative North Americans call the bearings, well, “bearings.” The parts on the engine that guide them are pedestals and their wedges. There is no room to faithfully model these parts, and so I have “bearing guides,” which get soldered to the backs of the frames.
Each bearing guide fits its bearing as perfectly as I can make it. Although there is no measurable variation in the width of the bearings, I made each guide to fit a specific bearing, and marked them with one to four dimples. Speaking of dimples, next time I shall etch these into the parts, saving myself five minutes with the drill.
The other improvement I will make the next time I design an etch is to create blocks of parts for each subassembly. These blocks should be mounted on a removable subsection of the fret, so they can be worked on in the fret until as late as possible. These bearing guides, for example, are much easier to finish while still attached to a handle, but the full sheet is rather unwieldy, and likely to get damaged if I work with it.
I had to make an extra guide because one of them turned out loose due to overzealous filing.