MechanicalRebuild shelfUnplug and unscrew

Neodymium magnet

Also called hard drive magnet, NdFeB, rare earth magnet.

The strongest magnet a normal person will ever pull out of the trash. A 3.5 in hard drive has two nickel-plated arcs on steel keepers. They pinch skin, they shatter if they slam, and they are effectively permanent at room temperature.

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.

Strong neodymium magnets. Hard-drive magnets slam together hard enough to blood-blister skin and shatter into sharp chips. They also wipe media and bother pacemakers.
Beryllium oxide in magnetrons. The white ceramic in a microwave magnetron can be beryllium oxide. Intact it is stable. Dust from cracking, sanding, or machining it is a permanent lung hazard.
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
Source	Hard drives first. Headphone and speaker drivers are usually ferrite, weaker for the size. Magnetron rings are strong and come with a beryllium warning on the tube they surround.
Grade	Unmarked, typically a high-N grade. Do not quote a pull force you have not measured.
Heat	A soldering iron can partially demagnetize a small one. A hard drive magnet shrugs at ordinary heat and dies near a few hundred °C or in a strong reverse field.

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

A clamp
A latch
A sensor target
Retrieving a screw
Holding a work light

Leave this one when

It is shattered. The shards are sharp and still magnetic, which is a miserable combination.

Buying a new one is the better idea when

Block magnets with a known grade, when you need a flat face and a repeatable force. Salvage arcs are free and awkward.

How to tell if this one still works

If it holds its own weight on steel, it is a magnet. There is no further incoming test.

Step-by-step on the bench: Separate hard-drive magnets

Tools you will want: Plastic wedge, A keeper plate.

Where people actually find it

6 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
Hard disk drive	Prize	2	always	Top and bottom of the actuator.
Laptop	Bonus	2–4	usually	Display lid and the bottom case, as latches.
Set-top box or streamer	Bonus	2	sometimes	Inside a DVR hard drive, if the box has one.
Mobile phone	Bonus	several	sometimes	Speaker and lid.
Headphones	Bonus	2	always	In the drivers.
Microwave oven	Leave it	2	always	On the magnetron.

Prize — take this firstHard disk drive2 · always
In this particular machine
Nickel-plated neodymium arcs on steel keepers. Desktop magnets are much stronger than laptop ones.
Where to look
Top and bottom of the actuator.
How to get it out
Slide sideways off the keeper with a plastic wedge.
The condition to expect
Permanent, unless they have been slammed to pieces.
Bonus, if you are already in thereLaptop2–4 · usually
In this particular machine
Small neodymium discs. Easy to lose.
Where to look
Display lid and the bottom case, as latches.
How to get it out
Note where they sat so the lid sensor still has a target if you reassemble.
The condition to expect
Strong for their size.
Bonus, if you are already in thereSet-top box or streamer2 · sometimes
In this particular machine
Open that drive as its own donor. The platters are not the prize.
Where to look
Inside a DVR hard drive, if the box has one.
How to get it out
Four screws, then the drive lid.
The condition to expect
The drive may be dying. The magnets are not.
Bonus, if you are already in thereMobile phoneseveral · sometimes
In this particular machine
Small discs.
Where to look
Speaker and lid.
How to get it out
Easy to lose.
The condition to expect
Strong for the size.
Bonus, if you are already in thereHeadphones2 · always
In this particular machine
Small, often neodymium on newer drivers.
Where to look
In the drivers.
How to get it out
Behind the cone.
The condition to expect
Good.
Leave it — present, not yours to reuseMicrowave oven2 · always
In this particular machine
Strong ring magnets. The ceramic in the tube can be beryllium oxide.
Where to look
On the magnetron.
How to get it out
Do not machine the tube. Prefer hard-drive magnets, which are a better shape and not attached to BeO.
The condition to expect
Magnets are fine; the tube is not your project.