Countersink Drill Bit
Countersink Drill Bits Buying Guide
Countersink bits come in a variety of stiles and sizes depending on the project, the screws you're using, and personal preferences. For utility shop furniture or other quick-and-dirty projects — especially temporary items — we often don’t care much about the screws. They can be visible or not, proud of the surface or not; sometimes, it just doesn’t matter.
But for most of our work, if a screw is going to be visible we want it to look good, seated smooth and flush with the surrounding surface whenever possible. Sure, you could forcibly drive a flathead screw flush, but that almost always tears the wood surface fibers and looks terrible. In hardwood, you might not even be able to set the screw flush. This is where countersinking (or its close relative, counterboring) come in. When you top off a pilot hole with a countersink, the screw head seats perfectly: all its surfaces contact the wood with the same amount of force, making for a strong attachment and a clean look.
Countersink Drill Bit Types
- Standard: These countersinks have a cone-shaped tip and cutting flutes that extend down the sides. They are designed to countersink an existing drill hole. Variations on this type of countersink are available for drilling all materials.
- All-in-one: These countersinks have a hole in the middle that accepts a smaller diameter (pilot) drill bit, and often a depth stop. They’re capable of drilling the initial hole and then countersinking or counterboring it.
- Tapered: Some pilot drill bits are tapered, which it's claimed makes for faster, smoother drilling. It also provides a larger “grip” area for a tapered screw – which gives stronger fixing – as long as you accurately match diameter and depth to the size of screw you’re using.
- Cross-hole: These countersinks don't have flutes but a single hole drilled through the head at a 45° dangle. Although called a “countersink,” these are actually used for deburring existing holes, usually in various types of sheet metal.
How to Differentiate Between Countersink Drill Bits for Wood and Metals?
As you are pretty clear about by now, different types of bits are suitable for different materials.
Hence, it is crucial that you get your things in order and decide which material you intend to use your bits on-metal or wood. If you require to work on both, opt for bits that work ideally on both materials. Or, you could just opt for a countersink drill bit set of numerous bits that are suitable for each material.
For example, carbon steel will be ideal for wood but not for metals. HSS or High Speed Steel can be an ideal pick for woods and soft metals. HSS with Black Oxide is great for metals and both soft and hard woods; while HSS titanium will remain sharper than the rest for longer.
Now the drill bits for wood and metal may seem basically the same, but closer observation will give away what material they are most suitable for. In case of appearance, bits may appear in multiple arrays of colors including gold, copper, black, silver, etc.
But you'll notice that usually, countersink bits for metals are black or deep gray in color. This is because they comprise special coatings of other substances such as Black Oxide or Titanium. Bits for wood, either hard or soft, usually tend to be silver as no special coatings are involved.
Another significant difference between the two is the tip design. If you look closely enough, you’ll find that drill bits for wood usually possess a pointed tip; also known as brad. This enables to cut the wood precisely inhibiting the wandering of the drill bit as it turns to make the hole.
The ones for metals, on the other hand, possess tips that are angled up to several degrees such as 135°, 120°, 118°, 110°, 100°, 90°, 82°, 60°, etc. so as to match the screw head angle.
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- Check the chamfer angle of your screw heads. Most are 82°, but metric screws are often 90°, and other angles exist. If your countersink angle doesn’t match, the screw won’t sit properly. If the screws are hidden, much of the time it won’t matter, but if they’re visible, it looks wrong. In hardwoods, it can even weaken the screw head, and in extreme cases cause it to break.
- Mark the position with a center punch first when drilling holes in metals. Solid models are tapped gently with a hammer; spring-loaded models are simply pressed until they activate.
- Work out the required depth carefully when doing counterbores. Too shallow and the screw won’t grip properly. Too deep and there’s a danger of it pulling through.
- Deburr holes, too. A countersink isn’t just for making recesses. One is also the fastest way to deburr a hole in sheet metal or pipework. A quick twist by hand is often all that’s needed.