MechanicalRebuild shelfHand tools, works as-is

Spring

Also called extension spring, compression spring, torsion spring.

Printers, battery contacts, mechanisms of every kind. A spring with no rate is still a spring you can try. Label where it came from if the machine might be reassembled.

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.

Sheet metal and glass. Case steel, shattered platters, lamp glass, and magnet chips cut deeper than they look.

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
Kind	Extension (loops), compression (open coil), torsion (arms). They do not interchange.
Rate	Unknown unless you measure force versus distance

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

Return springs
Battery contacts
A detent

Leave this one when

It is bent open or rusted at a stress point. It will break there.

Buying a new one is the better idea when

An assortment, once you need a rate rather than a lucky fit.

How to tell if this one still works

Flex it in the direction it was meant to work. It should return.

Tools you will want: Pliers.

Where people actually find it

5 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
Toaster and toaster oven	Worth it	1	always	Carriage return.
Flashlight	Worth it	2	always	Head and tail.
Inkjet printer	Bonus	several	always	Carriage and covers.
Washing machine	Bonus	2–4	always	Suspension.
Doorbell	Bonus	2	always	Return springs.

Worth pullingToaster and toaster oven1 · always
In this particular machine
A real spring.
Where to look
Carriage return.
How to get it out
Control it.
The condition to expect
Good.
Worth pullingFlashlight2 · always
In this particular machine
Battery contacts.
Where to look
Head and tail.
How to get it out
Clean corrosion.
The condition to expect
Good.
Bonus, if you are already in thereInkjet printerseveral · always
In this particular machine
Various.
Where to look
Carriage and covers.
How to get it out
Bag them.
The condition to expect
Good.
Bonus, if you are already in thereWashing machine2–4 · always
In this particular machine
Heavy. Useful, and they will leave a bruise.
Where to look
Suspension.
How to get it out
Control the rebound.
The condition to expect
Good.
Bonus, if you are already in thereDoorbell2 · always
In this particular machine
Small.
Where to look
Return springs.
How to get it out
They fly.
The condition to expect
Good.