Grind Forstner drills - that's how it works

Even the best tools lose their sharpness at some point. Of course, this also applies to Forstner drills. What makes these drills dull very quickly and how they can be sharpened, you will learn in detail in our contribution.

Sharpness loss by heating

When drilling with the Forstner bit you should always make sure that the drill is not hot under any circumstances. If the drill overheats, or even begins to glow, it usually loses its sharpness immediately.

Therefore always drill at the most suitable speed and absolutely try to avoid heating up the drill.

If you occasionally cool your Forstner drill in water, this usually does not help to avoid the consequences of overheating - the damage is usually already done when the drill reaches a high temperature for the first time.

Sharpen right

Proper sharpening of a Forstner bit is not that easy. Regrinded in this case, only the clamping surfaces. In this case, the sanding is always done "on the envelope" - which is exactly what only professional sanding services can do.

If you grind yourself, you should definitely make sure that the rake angle when grinding is around 30°. The cutting edges on the periphery should be gently sanded only from the inside.

After the grinding process, the periphery cutting edge should have about 0.3 to 0.5 mm overhang to the main cutting edge. For regrinding on the periphery you can also use a grinding pin.

Due to the complex geometry of the Forstner drill, a special tool must always be used for regrinding.

Sharpening at the sharpening service

Simple drills can cost around 10 to 20 EUR, depending on the diameter. If HM drills are to be reground, it usually gets more expensive, and costs are usually around 20 EUR. Very large diameters are often much more expensive. But always compare the prices of individual sharpening services and ask at your hardware store, if a cost-effective sharpening service is offered - many hardware stores offer this service.

Tips & Tricks

When using HM drills, the loss of sharpness when overheating is not as problematic. They have a higher stability even at higher temperatures. New models with a toothed or wave-shaped peripheral cutting edge do not overheat too quickly, leaving them sharp and sharp for longer.

Video Board: Performance Drill Bit Grinding