Should I Use Chamfer Mills Or Spotting Drills?

As you should already know by now (and as our parents used to say), there is a tool for every task. In most lines of work, once we find a technique or tool that works, we want to use them on everything we see. Which is another way of saying that if you have a hammer, everything looks like a nail.

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Machining is no different. Once we grow fond of a certain bit, we tend to find ways to keep using it. After all, who hasn’t used center drills for spotting? Those who are free of sin, please cast the first stone. The problem is that, when using the wrong tool, you will end up damaging your gear or spend more time changing tools than going through the material.

However, experimenting sometimes yields weird results, and there are indeed cases where we find tools that can yield better results than the ones deemed right for the job.

One good example is chamfer mills.

Chamfer mills are designed to remove sharp edges after we cut workpieces. After we perform a clean cut, the piece will probably sport a sharp, irregular edge. It is always preferable to chamfer out the side and give it a smooth and safe finish as a professional courtesy.

However, chamfer mills can also be used for spotting.

Yes, there are indeed spotting drills designed with a specific geometry that allows them to create smooth notches on your piece for later plunging. But chamfer mills can perform the same task and take you one step further in only one pass.

We know that punching holes is sometimes harder than just plunging your drill into the piece. In fact, it sometimes takes up to 4 different tools to make sure the hole is right where we want it and that the twist drill stays on course. Spot drills allow you to create a small notch on your piece so your twist drill has a fighting chance of staying in place. Otherwise, you risk having your tool walk off and miss the mark, which can cause misaligned holes, affecting the quality of the final part.

After you spot the hole, you can safely drive your twist drill into the piece. Then you need a flat bottom counterbore to remove the drill point or just finish the hole, and then give the hole a clean and aesthetically pleasing countersink so your screws sit flush with the part.

But, what if I told you there is a tool that can handle two of these tasks in one pass?

In some of our projects, we have been using pointed chamfer cutters instead of spotting drills as they allow us to spot and countersink in one pass. However, you must use a mill that has a larger diameter than the hole being drilled, and a wider angle than the drill following the hole. If your countersink has a narrower angle than that of your drill point, deflection might cause you to end up with a misaligned hole. One other problem with narrow angles is that they offer a small point of contact with the side of your drill, which might damage the tip.

Chamfer mills prove to be very versatile tools but they must provide increased accuracy if you hope to have consistent results all day long. That’s why we recommend carbide chamfer mills for this job. Carbide is extremely hard which prevents wobbling, chatter, or tool walking, drastically increasing the accuracy and productivity of your machine. Visit and find the best carbide cutting tools for the job at direct manufacturer prices.

For more information about Single Pitch Thread Mills and Variable Flute End Mills Please visit: Online Carbide.


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