Create double-sided floppies

The disks are already double sided - aka DS DD = double sided, double density. The cutout is only for the write-protect sensor to detect, inhibiting software writes if there is a protect tab, and allowing if there is a cutout.

One step further, you can mechanically (Disk ][) or electrically (5.25" drive) adjust your disk drive to ignore the write-protect altogether and write to a disk whether or not there is a cutout.

Cheers!

and if you wish to go a step further , on the Disk ][ Drives , you can snip the write protect switch inside the drive , add a SPST switch to it , and with the flip of a switch , over-ride the write protect mechanisim! It's a nice feature too have , too be able to write to non-clipped disks! Makes all your disks look nice and professional.

You can tape over the hole on the floppy opposite the write protect switch to turn a DD floppy into a single sided floppy that works with the old old macs. I don't know if the what you're proposing, the opposite, is true.

I remember doing this with 5 1/4" floppies on my Atari 8-bit machines. Yes, it does work, but reliability was spotty.
Whether it's true or not, I remember reading the explanation was different batches were rated DS or SS depending on factory sample testing. While the fail rate may relegate a batch to SS packaging, there was no physical difference other than a higher potential fail rate of the second megnetic surface (and the extra notch, of course).

If you look through the old computer magazines, several companies sold disk punches for this very purpose.

So, the one "good sounding" reason the disk and drive manufacturers had for saying that "flipping your disks" was a bad thing was that 5 1/4 inch floppy disks have a dust-absorbing lining inside the plastic envelope. Supposedly (the argument went) by spinning the disk inside the opposite direction of its "normal" direction of travel (which of course happens when the disk is flipped over) the dust which collected on the paper lining that otherwise would of stayed there would be dislodged and recoat the disk. And more ominously, collect on/scratch/whatever your disk drive's read-write head.

How much of a problem this actually was in practice I can't say. I used to notch the disks for my Atari 800s, but all I ever kept on those disks were games which spun the disk once while loading. It's also true that a few manufacturers actually sold pre-punched flippy floppy disks, which implies that either those disks had a differently formulated dust jacket material or that the whole dust argument was bunk in the first place.

--Peace

I really do not believe that that the dust jackets were made amy differently. They just help to collect dust. If you had a lot of it, then there is possiblity of a bit of coming loose.
I think that the manufacturing process got better over time, so it did not matter if you used both sides. The manufactures wanted to sell more disks. Drop prices, make them notched for both sides.
I can tell over time (Till this day) I have had more 3.5 800k fail then 5.25 140k. The 3.5 were 5-8 years younger then 5.25s. For everyone old used and abused 5.25 that failed I have at least 10 3.5 disks that failed.

I've "dissected" many of those old 5 1/4" disks
and have not found any differences in the way
they were manufactured. Also didn't have any
problems with failures when punching disks to use
both sides. I still ahve a disk puncher for my
Apples. Made/marketed by "SunCom". A division of
Sun Microsystems? It's been quite a while since
I got this and I jsut can't remember.

Don't be afraid to punch and use those old floppies!
Now that they are obsolete, you should be able to
find them for next to nothing on the secondary
market. Possibly even Radion Shack still ahs some
around. Tandy was one of the last computer marketers
to get away from the 5 1/4" format, plus they did
support the "hobby" market. That's where I got my last
new batch.