How can you recognize a good metal drill bit at first glance?
How can you recognize a good metal drill bit at first glance?
Yes, this question is asked frequently and it’s especially important when making a purchase decision on the spot. Let’s clear up two common “prejudices” right away: price alone is not a reliable criterion for assessing quality, and certification marks such as VPA or TÜV say very little about the actual performance of a product. Drill bits are mass-produced items. Testing institutes can only test sample drill bits. Whether mass production consistently meets these criteria is another matter.
The best approach is to examine the product yourself and pay attention to the following points:
1. Markings on the drill bit
Is the marking clearly legible? Is there any indication of the distributor or codes for traceability? Some manufacturers mark their drill bits with codes to allow tracking and to identify at which production site and when the product was made. This is a clear indication that quality assurance is taken seriously and that a proper strategy is in place.
2. Finish of the drill bit
Next, look closely at the finish—especially at the drill tip. The drill tip should always appear symmetrical, and the cutting edge should show a visible clearance angle. In other words: the main cutting edge should fall back against the direction of rotation. If that’s not the case, the drill won’t cut properly—it will only scrape.
3. The drill flute
At the exit of the flute you can easily recognize whether the drill has been rolled or ground. If the exit is more rounded, it is rolled. Ground drills are more expensive because the production process takes longer. They are usually more precise and offer higher concentricity. Rolled drills, on the other hand, have a better grain structure and are more robust in use.
4. Material of the drill bit
If you’re unsure about the quality of the material, there’s a simple trick to check whether it is high-speed steel (HSS) or regular tool steel: hold the drill bit against a grinding wheel and observe the spark pattern. The differences become obvious very quickly. Try it out with different materials!
Sometimes drill bits are not hardened properly, insufficiently hardened, or hardened incorrectly. Here, too, there’s an easy test: take a file and cut a notch into the drill. If this is easily possible, the product is not hardened (or insufficiently hardened). If the drill breaks very easily, then it is too hard—this happens when the bit has been hardened but not tempered, or not tempered often enough.