BH2 Fine Focus Finger Drive Adapter

Background:
Did you know the fine focus knobs on the Olympus BH2 have precisely 51 ridges around their diameter? I do. I counted. I find the BH2's fine focus knobs to be a little narrow for my tactile sensibilities. Many more modern microscopes now have fine focus knobs with finger depressions that allow for long travels of the fine focus without interruption to re-grip the knob. I wanted to take a stab at emulating that.

This part:
This is an adapter that fits over the fine focus knob on the BH2. It has internal ridges and a slight conic taper matched to the BH2 fine focus knob, so it snugs up only at the very end of travel and can easily be removed thereafter. It features 8 spherical finger depressions about 3mm deep and canted in slightly toward the microscope. The base tapers away from the knob so that the micrometer scale is still easily readable when it's installed. The outer diameter forms a circular profile that can be used for fine position adjustments.

Important:
You should not install this on a BH2 that hasn't been renewed via a thorough cleaning and regreasing of the coaxial focus system. When properly greased, the fine focus knobs will turn very easily, making this adapter work smoothly. If the knobs don't turn with a light touch, your finger will need to work too hard. Your knobs also cannot be deformed or dented as this will interfere with fitment. The fitment on this should be lightly snug at the end of travel and flush at the wide base of the knob - if you print yours and it doesn't seat easily, put in some X-Y hole compensation and reprint - don't force it on.

Material and Post-processing: Print this with a low friction material - regular PETG is probably fine - I used PETG-PTFE for mine. An optional but highly recommended step is to take a dry (no polishing compound) felt polishing wheel or bullet to the finger depressions using a rotary tool (about 10k RPM seems to work well) to buff down the layer ridges until they're very smooth. This improves feel tremendously. Apply in brief strokes so you don't melt the plastic.

Printer settings: Outer walls first, avoid crossing walls, random seams, finest layer height you can go or use variable layers set for maximum quality. Use monotonic or rectilinear for the top surface pattern - this works better than concentric for making a smooth surface at the bottom of the finger depressions. I printed it with a .6 nozzle.

This is a work in progress, I think the ergonomics could be improved - if you print one and try it out, please provide some feedback.