I used the longest countersink for about half an hour before it broke like cheap plastic. I drilled holes in 2x4 and 2x6 for a backyard garden planter so it wasn't exactly industrial use. For reference, I used my DeWalt 20V MAX cordless drill (DCD985B) on the lowest setting (1) to drill holes directly into the wood. Luckily I was able to finish the job with a medium countersink and it didn't break - at least not yet. I'm usually amazed at the quality and durability of DeWalt tools. This is my most disappointing experience with a DeWalt tool to date and I hope this lack of quality is not repeated in future purchases. Unfortunately, I cannot recommend these countersinks.