Review on 🔧 Accusize Tools Straight Metric Counterbore 508S 007M by Brian Kingsford

This is amazing. Not only are they amazing for the price, they make great countersinks and the low price is an added bonus! I use countersunk screws a lot since I bought them last summer. If you want to make your own tools, that's great. Your trick is going low (500 rpm or so) and matching the size of the through-bit to the pilot bit on the countersink.