Just like every other cutting tool in the shop, drill bits get dull and do not cut like they used to. The worst thing to do is go out and buy a new set because you think the ones you already have are shot. Many people don’t know how easy it is to sharpen your own bits which will save you money and a trip to the store.
In order to sharpen your bits you’ll need a Bench Grinder, while there are tools specially designed to sharpen drill bits they end up not being worth the cost. Taking the time to learn how to properly sharpen them yourself will more than pay for itself the next time a bit becomes dull.
To show the common problems dull bits can cause, I found four drill bits each having a different problem that sharpening can easily fix.
The first bit shown would not even drill through a piece of 16 GA steel, it started to cut through but stopped about half way through. At this point there weren’t any more metal shavings coming from the hole. If you look closely at the cutting surface, you will see that the outer edge of the cutting surface is rounded over this is what caused the bit to stop cutting. Look how the top cutting edge.
Sometimes only one part of the cutting edge becomes dull or chipped. On this bit just the outer corner chipped, depending on the quality of drill bits you have this may happen more often. Look and see how the tip of the bit and first half of the cutting edge is still in relatively good shape but then the outer edge is almost completely chipped off.
With age and use the tip of a drill bit will begin to dull, especially if you drill metal often. Overall the cutting edge of this bit was in good shape but the tip was rounded over. This will prevent the bit from starting the hole and could possibly begin to wander if a pilot hole was not drilled first.
Another key element in drill bit performance is the angle of the tip. This bit was previously sharpened but was done so a little too flat. This can cause issues because the smaller angle on the cutting edge will cause the bit to try to remove too much material at a time, causing the drill bit to bind and grab hold of the material you are drilling. This can be especially dangerous if you are using a drill press, the bit could possibly grab the material and overcome your grip causing it so spin at the same rate the drill is spinning.
The proper drill bit angle is between 59º-60º, providing a good middle ground between drilling speed and drill bit life. (For more specific applications and drill bit materials, different angles may be better suited but for an all purpose but this is ideal)
You can see here that before, the first three bits did not even pierce the metal and the forth one drilled too quickly and left an uneven hole. After they were sharpened each had zero trouble cutting through this thin piece of metal.