I made this adapter to easily attach small self-tapping screws and mount a wheel plate to an IKEA shelf. This way, there's no risk of screws colliding with bottom shelf or needing to pre-drill holes.

These adapters are for attaching 4" coaster wheels with an 82x102mm mounting plate. The average offsets are 15mm on the narrow side and 13mm on the wide side.

I used this to put wheels on an IKEA ALEX unit. The adapter is shorter than the original legs, so you can keep the adapters on if you ever want to remove the wheels.

To make modifications, you'll need the "hardware.scad" file (provided) and the Round-Anything library installed in your Openscad path, which you can find at https://github.com/Irev-Dev/Round-Anything.

BOM per wheel

8x self-tapping screws 3mm diameter 10mm length 

4x M5 nuts

4x 10mm M5 bolts

4x M5 fender washers