You can try to chuck a #61 bit in a 1/2″ chuck, but it’s probably an exercise in futility — the chucks just aren’t designed to hold such small bits. To make centering their (and other companies’) micro drill bits a lot easier, Gyros makes a mini drill bit adapter. This adapter’s 1/8″ shank also allows you to chuck these micro bits in a rotary tool like a Dremel.
The adapter accepts bits from 0″ (#61) to .0390″ (#81). Gyros precision-machines the shank and collet from a single stainless steel billet and dynamically balances the finished chuck to ensure that it spins true and vibration-free up to 35,000 RPM.
Made in the USA, the mini drill bit adapter will run you about $8.