Tektronix Zoom Knob
thingiverse
Quick mock-up of a tektronix zoom knob, should work on the MDO/ MSO/ DPO 3000, 4000. and 5000 series. These things are decently easy to pull out/ break, and I've seen a number of college labs where mischievous students do just that. This design doesn't really improve on the strength or ease of removal, but if you only need to replace one or two knobs, it can be cheaper than buying a new set of them. I have included the sketchup file (yeah, I know, sketchup isn't the best for this but w/e, its what I know), so feel free to edit the model, I can imagine adding a better grip might be nice, I just followed the default tektronix knob pattern.
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