Carbide Drills

In a carbide tipped drill, unlike the solid carbide drill, only the head or tip (also called the crown) of the bit is made of carbide. One can get a brazed tip or an exchangeable drill bit tip.

A brazed tip means that there is another metal welded to the end of the other. Drills with brazed carbide tips generally use steel as the main structure to which the carbide is welded. This allows for a lower cost as compared to the solid carbide drill, while still retaining good accuracy. For comparable diameters, the tolerance of the brazed carbide tip is about twice that of the solid type. One of the problems with the solid carbide drill, is that it tends to be brittle, and can therefore break easily. The brazed carbide drill bit with the steel body, allows for more flexibility and is therefore not just a cheaper option, but also more suitable depending on the task to be performed. For eg. they are more suited for working with lathes. Brazed drills have two cutting edges which are symmetrical. This gives a self-centering geometry, and it is a very stable design. This stability allows for drilling at top feedrates if the entrance is not angled.

The replaceable or exchangeable drill bit tip, unlike the brazed drills, allows for the crown to be replaced, as it is not welded on. There are a variety of crown sizes available, which means that you could use one drill for multiple hole sizes. Whereas a brazed tip or solid carbide drill might require regrinding every so often, with the exchangeable crown drill, one simply replaces the crown. It costs about the same to replace the crown as it does to regrind the solid or brazed drill. Replacing the tip is more advantageous in that regrinding can only be done a certain number of times, and each time it is done, the accuracy and performance of the drill deteriorates. Like the brazed types, these drills also have self-centering geometry and can handle drilling at top feedrates.

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