MicrobeHunter.com Microscopy Forum

I wonder whether the "rubber focus knob cover" often added on top of the fine focus knob of a microscope to provide a more precise/more comfortable handling of the fine focus has a specific name. I am aware that "rubber focus knob cover" is occasionally used for microscopes, but I would like to know whether this accessory has a more specific name. More than half of Google hits take me to rubber covers for the Ford Focus gear stick, and almost all the rest to rubber knob covers for electric guitars.

It's a fondom.

Among search word combinations tried for Google, this worked best:
microscope fine focus knob cover

.. but with a measure of the knob's outer diameter, e.g. 30mm,
consider searching for rubber tubing with that inside diameter (or slightly less).
If searching US sites, also consider equivalent inch dimension, e.g. 1.25 or 1-3/16" for 30mm.
These products are specifically for such applications:
https://re-grip.com/purchase/

Thanks for the suggestions. Another term I just found is "fine focus rubber boot".

My interest in this "thing" at the moment is to reversibly connect a stepper motor to the fine focus knob of an Olympus BX-50 without any modification of the microscope. I am building an adjustable stand for the motor, based on 2020 aluminum profile (not unlike the Wemacro MicroMate, but IMHO the latter is unnecessarily sturdy and very expensive for what you actually get). Moving the stand away frees the fine focus knob for manual use if needed. I have an extra Olympus rubber boot that I intend to attach to the motor axle, but have not decided exactly how to do this.

With a 400-step/revolution stepper motor, disconnecting the motor from the controller allows the opposite fine focus knob to be manually turned without too much effort (but you can still feel the motor "steps" because of the permanent magnets in the motor). For a lengthy manual operation session, I would rather pull away the motor stand entirely.

Initially I was planning a magnetic connection between motor and fine focus, with a donut magnet on the motor axle and a steel washer on the focus knob. It does turn the focus knob without slippage, but the small magnets I got are way too strong to safely pull them away from the washer.

enricosavazzi wrote: ↑

Sat Aug 13, 2022 7:31 am

reversibly connect a stepper motor to the fine focus knob of an Olympus BX-50

Find elastomeric tubing which grips that focus knob; cut a short length of that
to couple a spool of matching diameter attached to the stepper motor shaft.