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The other day I was struggling to remove the head from a bolt that someone had overtightened. Trying to unscrew the bolt in the conventional manner only ended up destroying the phillips head of the 5/16 bolt. I tried all my special bits, most of them described as hardened, and none of them would do the job. A couple of the bits were brand new. I found this guy on YouTube who had run into the same problem. He eventually got a set of bits for drilling glass and ceramic tile. They had little carbide blades. He demonstrated how they worked so off I went to get a set of my own. I was astounded when I was able to remove the head of the bolt in no time. This is one of those times when YouTube really came through for me!

Show pictures of the work and the tool. What name, brand, etc?

I am writing to share some observations I’ve made regarding the performance and durability of various drill bits, particularly in comparison between those manufactured in the USA and those sourced from overseas. My perspective comes from 27 years of experience as a machinist.

I’ve found that, generally speaking, the majority of screws and bolts encountered are no match for drill bits crafted from High-Speed Steel (HSS) manufactured here in the USA. In contrast, I’ve experimented with some of the less expensive, imported drill bit sets – a recent example being a titanium-coated set purchased for around $20 from Harbor Freight. While the titanium coating initially suggested a degree of resilience, my experience over the past couple of years has been quite different.

These imported bits have proven to be prone to premature dulling and breakage. On more than one occasion, I've struggled to drill out a stubborn screw or bolt using these bits, only to then successfully complete the job with a USA-made HSS bit. The difference in performance was significant and undeniable.

This experience reinforces my understanding of the quality and consistency found in American-made tooling. While the initial price point of imported sets may be attractive, the long-term value and reliability pale in comparison to the more robust American alternatives.

Of course, in my professional experience, when dealing with particularly hardened or difficult materials, we often turned to solid carbide drill bits. These are undoubtedly a more costly option, but their effectiveness in such situations is unmatched. However, it is equally important to acknowledge that carbide bits are brittle and shatter easily if not used with proper care and at controlled speeds.

My intention in sharing these observations is to provide valuable feedback based on real-world use. I hope this information is helpful.

I have good luck with cobalt steel bits. I think I’ve mostly bought DeWalt brand but probably have some Irwin as well.

The titanium HF bits are pretty near worthless in steel.

What Phat said is true. I too have been in the metal machine trade since I was 16. What I have seen is that folks that have not been around any metal cutting machines will run a drill way too fast with no lubrication. Most drill presses and hand drill motors will turn too fast, even with a good quality bit. The over seas cutting tools are OK for wood, but not for metal.

So here is my suggestion for a Allen bolt. Like Phis said, Carbide will get it done, slow rpm, lube and a lot of feed pressure.

Don