YouTuber builds functional floppy disk from scratch using CNC and DIY magnetic coating

[midian182]

In context: If there's one thing YouTube has shown, it's that almost anything can be built by yourself at home if you have the time, skill, and required parts. Take, for example, polymatt, who managed to build a 3.5-inch floppy disk from scratch.

Outside of their use in some legacy systems and among retro enthusiasts, floppy disks are pretty much obsolete these days – many younger people know them only as a save icon.

But polymatt wanted to see if he could create one of these disks from its bare components. He began by disassembling a commercial floppy disk to study its internals and construction, giving him a blueprint for what he needed to replicate.

The first step of the construction was the recreation of the outer shell. polymatt used CNC milling for the enclosure, which looks great.

Then came the most difficult part: creating the magnetic disk core. A 5-watt laser cutter shaped a thin disk from PET film – floppy enough to work mechanically. It was then flattened and heat-treated using a 3D printer to achieve uniform thickness.

Making the magnetic coating was a particularly impressive and complex feat. It involved mixing iron oxide powder into a binder solution composed of PVA (polyvinyl alcohol), isopropyl alcohol, glycerin, and Tween 20, which is a common surfactant. After adjusting ratios, going through several iterations, and degassing the solution to remove bubbles, polymatt applied the final solution to the PET film disk. The coating measured around 5 – 6 microns thick, approaching the roughly 2-micron thickness of commercial disks.

Initial attempts were unsuccessful as the coating was peeling off at 300 RPM. To fix this, polymatt scuffed the PET surface, heat-treated it, and carefully applied the coating and drying process. This improved adhesion enough for the disk to spin and, critically, store and retrieve small amounts of data.

With the coated disk ready, he assembled it in the aluminum shell, added a center ring, and tested the disk in a real drive. Thankfully, it spun and proved functional. While not flawless, it did demonstrate that homemade magnetic media can work – if you have the resources.

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YouTuber builds functional floppy disk from scratch using CNC and DIY magnetic coating

 

[kinetix]

It produced poor-quality results because:
1. He used aluminum for the body. It should have used plastic.
2. The way he disperses the fluid over the surface, by hand. The dispersion should have been achieved by rotating the surface at high speed and allowing drops of liquid to fall into the center, or the contact/writing area, similar to how silicon wafers are manufactured during chip manufacturing.

 

[onebignerd]

While I admire the resourcefulness and ingenuity, it has little if any functional value.

It produced poor-quality results because:
1. He used aluminum for the body. It should have used plastic.
2. The way he disperses the fluid over the surface, by hand. The dispersion should have been achieved by rotating the surface at high speed and allowing drops of liquid to fall into the center, or the contact/writing area, similar to how silicon wafers are manufactured during chip manufacturing.

Spinning the disc at high speed would never allow the liquid to fall into the center, the centrifugal force would send the liquid out to the edge of the disc. NOT inward to the center.

 

[kinetix]

While I admire the resourcefulness and ingenuity, it has little if any functional value.

Spinning the disc at high speed would never allow the liquid to fall into the center, the centrifugal force would send the liquid out to the edge of the disc. NOT inward to the center.

And that's what I said. The drops will fall in the center or in the area where they are desired. Centrifugal force will disperse them over the surface and expel the excess, creating a very thin film.

 

[onebignerd]

And that's what I said. The drops will fall in the center or in the area where they are desired. Centrifugal force will disperse them over the surface and expel the excess, creating a very thin film.

Go ride the spinning wheel at a carnival or amusement park. When at full speed pull your self off the wall, walk to and stand in the center of the wheel. Good luck!!

 

[kinetix]

Go ride the spinning wheel at a carnival or amusement park. When at full speed pull your self off the wall, walk to and stand in the center of the wheel. Good luck!!

for a home made example, please, go to 1:25

 

[PurpaFur]

Go ride the spinning wheel at a carnival or amusement park. When at full speed pull your self off the wall, walk to and stand in the center of the wheel. Good luck!!

So just put the drip in the center, then spin it? Not that hard to understand.

 

[onebignerd]

And that's what I said. The drops will fall in the center or in the area where they are desired. Centrifugal force will disperse them over the surface and expel the excess, creating a very thin film.

So just put the drip in the center, then spin it? Not that hard to understand.

Placing a drop in the center is not what is being said; "...by rotating the surface at high speed and allowing drops of liquid to fall into the center...". Placing a drop in the center and spinning the disc to have liquid "fall into" the center are two different things! The act of spinning does not allow liquid to "fall into the center".

 

[PurpaFur]

Placing a drop in the center is not what is being said; "...by rotating the surface at high speed and allowing drops of liquid to fall into the center...". Placing a drop in the center and spinning the disc to have liquid "fall into" the center are two different things! The act of spinning does not allow liquid to "fall into the center".

Placing a drop in the center is EXACTLY what is being said. If I drop a drip onto something, it could be said that the drip "fell". So a drip falling into the center means it was dropped there. The spinning comes AFTER the drop falls into the center.

Reading comprehension is more than just reading the words. It helps to infer the meaning behind the words.

 

[onebignerd]

Placing a drop in the center is EXACTLY what is being said. If I drop a drip onto something, it could be said that the drip "fell". So a drip falling into the center means it was dropped there. The spinning comes AFTER the drop falls into the center.

Reading comprehension is more than just reading the words. It helps to infer the meaning behind the words.

No, the fluid "dropping" into the center is said as an effect of spinning the disc, NOT being placed there. "...The dispersion should have been achieved by rotating the surface at high speed and allowing drops of liquid to fall into the center, or the contact/writing area" -kinetix, August 13, 2025, the source of my initial comment.

My reading comprehension does not find any mention of a drop being placed before spinning. Read the comment above and see for yourself!

 

[onebignerd]

And that's what I said. The drops will fall in the center or in the area where they are desired. Centrifugal force will disperse them over the surface and expel the excess, creating a very thin film.

Placing a drop in the center and letting it disperse is not what you said, re-read step 2 of you own post.

 

[PurpaFur]

No, the fluid "dropping" into the center is said as an effect of spinning the disc, NOT being placed there. "...The dispersion should have been achieved by rotating the surface at high speed and allowing drops of liquid to fall into the center, or the contact/writing area" -kinetix, August 13, 2025, the source of my initial comment.

My reading comprehension does not find any mention of a drop being placed before spinning. Read the comment above and see for yourself!

Guess what? You can place a drop WHILE it spins. Crazy.

Use just a tiny bit of inference and quit being pedantic.