Floppy and Opirical dive stepper resolution?

Hi everyone,

Edit: well not sure what happened with the title, it should have read Floppy and Optical drive stepper resolution.

I'm toying with the idea of making a DIY laser engraver from parts of old floppy and CD/DVD drives. There are some build tutorials on Youtube. Does anyone know what kind of accuracy the stepper motors in these devices can move? Is it anything like microns?

Cheers,
Ed.

A quick search shows the spacing between consecutive "tracks" on CDs and DVDs to be 1.6 and 0.74 μm respectively. Assuming a single step per track for the stepper motor, that would also be its linear resolution.
I didn't quickly find the same figure hard-written for floppy disks, but e.g. for a 3.5" disk the boxes read 135 TPI, so with 135 tracks per inch you'd equivalently have 135 single-sided tracks per 2 inches or 134 motor steps per 2 inches which gives about 380 μm.
For 5.25" it's 48 TPI I think, so in that case it would be around 1080 μm, just above 1 mm.

Wow!, that's brilliant?

Thank you very much.