Microtome cassette holder (PROTOTYPE)

We got a microtome at work but the clamp didn't fit the cassettes that our paraffin blocks were already mounted on. This adapter is designed to fit a Yidi Rotary Microtome YD-202 (also marketed at Brunel YD Rotary Microtome).
The fit of the parts needs a little work but I only need to make one so it would take me longer to fix in silico than to get the file out. You will need to sand the surface of the rider and the recess it fits into (sorry you will need to do a fair bit of test fitting, take your time and don't force it). You may also need to drill out the holes if they are a little tight (3.5 mm diameter bit seems to work nicely for the M3 screw). The parts were designed for PLA printing with 50% infill.
You will also need 2 M3 nuts (one fits inside the main body of the adapter through the slot in the front (caution tight fit and be careful not to push it in too far) and the other is to hold the knob on the end of the long screw), a 50 mm long M3 screw, a washer and a spring (I used one from an old pen). Not sure if it works in the microtome but it clamps the TissueTek cassette I had to play with. There may be a few errors in the files but Cura 2.5.0 seemed to slice the stl files OK.
Update: Seems to work in the microtome (see blurry phone-camera picture). I've also included a model of the cassette that I used while designing the holder, I've not printed this and it is only included so you have an idea of the style of cassette that the holder was designed to grip.
Update 16/10/17: I've included two modified versions of the "rider" which should hopefully resist snapping.

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