Seeing small round magnets for little money made me think. After trying them on a metal board, I decided to give them a chance to improve my scooters oil purification.
Said that, went in the workshop and tried to catch small iron shavings only with those magnets popped on my spare oil plugs. It worked (pls see pics).
Next step was to put plugs into my ancient lathe.
(btw: this lathe was bought 1908 by my great-grandfather and survived several economical crises and two WWs more than onehundred years in my family)(for more precise lathework I use a friends CNC lathe).
Predrill, final drill with a 8mm flat drill...
Ready to put magnets into their place. And yes, they collect small specks of iron.
On the motoroil plug I secured the magnet with some punches. If they really, due to de-magnetising from heat, leave their place, nothing can happen.
For this reason I chose the outer side of my plugs.
How they work in situ, next oilchanges will show.