Lego Microtome

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.

Best wishes