UPDATE 2021-05-03:

I uploaded modified version of microscope clamp, where it is clamped and secured by screw.

UPDATE 2020-10-06:
Because of many asks for source files I decided to publish f3d (Fusion 360) project file.

UPDATE 2020-09-12:
Somebody asked me to add spur hear with larger hole. The inside holde diameter of Spur Gear (10 teeth)-more-clearance.stl is now 0.5 larger.

Very rigid and stable microscope stand for cheap USB Microscope. This design requires some additional parts:

2 x 10mm x 21cm steel rod (for Z axis)
2 x 10mm x 15cm steel rod (for Y axis)
(You can order here 2x40cm and cut them by yourself)
2 x LM10UU linear bearing (link - optional)
3 x M3x30 screw (link)
5 x M3 nuts (link)
2 x M5x20 screw and nut (screws, nuts)
2 x wood screw 3x30
1 x plywood plate (20x20cm is suitable for me, but you may want to use other dimensions)
4 x rubber legs (link - optional)

Some parts may need to predrill the holes using 10mm, 5mm and 3mm drill bits.

Assembly:

• using the bottom_coupler part as a template, drill holes at plywood plate and screw it using wood screws
• attach the rods (21cm) and the rack part to the coupler, screw the rack using M5 screw and nut
• slide the carriage on the rods and rack
• attach top coupler (cap) and screw ii the same way as bottom one (using m5 screw)
• put the gear in place (between two carriage arms) and slide the shaft with knob through the carriage and the gear
• attach two rods to the clamp (you may want to glue them if they are loose) and finaly put the clamp with rods into carriage holes
• assemble the set M3 screws, nuts and printed knobs and screw them into carriage into right place to be able to lock the position.

The idea has been taken from USB Microscope Adjustable Base by Bcjams