MechanicalRebuild shelfUnplug and unscrew

Lens and optical glass

Also called camera lens, fresnel, scanner glass, magnifier.

Real glass from cameras, projectors, scanners, and overhead-projector Fresnels. Coatings are soft. A Fresnel from an old overhead projector is a large, light lens and also a way to start a fire if you leave it in the sun.

If you are new to this category

Rods, gears, belts, magnets, screws, and boxes. Printers are the best source of straight steel rod and toothed belts. Screws from a laptop are tiny and specific; a random screw in a laptop hole strips the plastic. Bag them by the machine they came from.

If two parts were meshing or riding together, keep them as a pair. A gear from one toy rarely fits a gear from another.

Inside a hard drive

The two curved blocks on the steel plates are the magnets, and they are the prize. Slide them apart. Do not pry straight up. The flat coil on the arm is a short-travel motor. The platters are not a useful material, and on some drives they are glass.

Heaters without their cutout. Nichrome and tubular elements are happy to start a fire if the thermal fuse or tip-over switch is left out of the new circuit.

Specification. The right-hand column is what is typical. The label on the part in your hand wins if they disagree.
What to look for	Usual figure
Camera	Multi-element, aligned. Removing elements from the barrel makes it a paperweight of good glass.
Fresnel	Concentric grooves. One side is the lens. Scratches kill the image.
Scanner	Flat glass, surprisingly useful as a platen or a small window

Volts are electrical pressure, amps are how much current is flowing, and ohms are how hard the part resists that flow. A higher voltage than the part was built for is how salvage parts die on the bench. If a cell in the table says “read the stamp”, that stamp is the whole specification.

What people actually use it for

Optics experiments
A condenser
A window
Leaving the camera lens intact as a lens

Leave this one when

Fungus inside a camera lens (the spots with threads). It etches the coating and it spreads.

Buying a new one is the better idea when

A lens of known focal length. Salvage glass is for when the focal length can be whatever it is.

How to tell if this one still works

Look through it at a straight line. Fungus, separation (rainbow patches), and cracks are the rejects.

Tools you will want: A blower, not your shirt.

Where people actually find it

4 notes, most useful first. “Leave it” means the part is in that machine and you should not take it: it is dangerous, worn out, or only useful if you already know that exact repair.

Harvest at a glance
From	Call	How many	How often	Where it sits
Digital camera	Prize	a group	usually	The barrel.
Flatbed scanner	Bonus	1	always	The glass bed.
Webcam	Bonus	1	always	In front of the sensor.
Flashlight	Bonus	1	always	The bezel.

Prize — take this firstDigital cameraa group · usually
In this particular machine
Several glass elements. Fungus is the reject.
Where to look
The barrel.
How to get it out
Keep the group intact if you want it to be a lens.
The condition to expect
Fungus etches coatings.
Bonus, if you are already in thereFlatbed scanner1 · always
In this particular machine
Flat glass, useful as a window or a platen.
Where to look
The glass bed.
How to get it out
Lift straight up. It chips at the corners.
The condition to expect
Scratched but usable.
Bonus, if you are already in thereWebcam1 · always
In this particular machine
A tiny plastic lens. Alignment is the value.
Where to look
In front of the sensor.
How to get it out
Leave it.
The condition to expect
Scratched lenses are why the image is soft.
Bonus, if you are already in thereFlashlight1 · always
In this particular machine
Plastic or glass, plus a reflector.
Where to look
The bezel.
How to get it out
Keep the reflector with it.
The condition to expect
Scratched.