A microtome is a machine which cuts (usu.) biological specimens into very thin sections. The sections are typically mounted on microscope-slides.
This was an idea I had, I did it, and I've demonstrated it with garlic
It creates slices 250 microns thick*
If anyone is actually thinking of building one of these see the last step. You can also PM me if you need more
Step 1: Construction: Base and Mount Runners
The specimen sits on a platform which is cranked forwards by gears. The mounting plate is driven by a rack and pinion mechanism geared very low from a hand crank, such that it moves .25mm with each turn of the handle. The platform rests on the red smooth-faced strips, which were lubricated with Johnson's Baby Oil (paraffin).
These images show the base of the device and the red runners for the specimen platform, also the final drive to the rack.
Step 2: Construction: Mount Plate
The plate upon which the specimen is mounted is essentially two smooth runners (lubricated as the previous step), and a rack.
Being Lego, the plate can be easily customised to hold a variety of samples.
Step 3: Construction: Upwards Towards the Gear-train
Not much to see in this step, I tried to get LDD to work but it hangs ever time (without fail). Perhaps using red instead of black would have been better?
In this sequence you see the front rails that hold the blade assembly being added (yellow and grey)
Step 4: Construction: Gear-train
Most of this is low-gearing from the hand-crank.
Step 5: The Blade
I hacked a disposable Bic safety razor for a blade (note that once these blades are out of the plastic, the word "safety" no longer applies - I cut myself twice through carelessness.)
Step 6: Construction: Finishing
In this step (for the purposes of publishing) I got tired of tedious image-editing, and I'll probably never feel like improving the look of these...
All the way to the end:
Step 7: Additional
With the rack-drive movement can be a little "lumpy", which is why I oiled it. A screw-drive would be better, or something with a worm-gear in it.
The gear-train to the blade cranks is a bit too long: all the gears make it a bit loose. It would work better with lever connections.
The blade assembly (grey) needed glue - it picked-off afterwards, but it's not strong enough without.
As you can see from the video it does work, but I needed to be a bit careful.
Your main considerations are:
A good solid platform that is fairly tight
Similarly for the blade
A lot of reduction from the crank. I work out 3 x 5:1 giving 125:1
Disposable razors tend to be held together with little plastic rivets. You can find these as round blobs on the underside - cut these off with a sharp knife and carefully prise the thing apart with the knife. These blades are very sharp and you'll tend to see blood before you feel anything.
To glue it on - I put the blade and Lego on a sheet of cling-film stretched over a tile, and carefully dribbled 2-part epoxy down the edge.