Tech Tip: Understanding Milling Insert Nomenclature - carbide insert terminology

2024-07-26 07:12:45

A brad or spur point bit is the most popular wood drilling tool. This wood drill bit can be identified by the small, pointed tip designed to penetrate through the soft timber. A closer inspection reveals spurs that can be found on each side of the bit. The spurs are designed to grab the wood and carve downward to get a smooth, clean result.

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Masonry bits are also used on granite countertops, marbles, and tiles as they are made from stone. This type of drill bit is used to punch into masonry or stone materials to hang pictures, put up shelves, and other items.

Using the right tool for the right job is not only an axiom, it may save you considerable time, effort, and expense. If you need to drill holes in wood or masonry, then only use the bits that are designed to drill into that material.

As you can see in the above image, the tungsten carbide cutting tip is ground at angle with no spur point in the center. Unlike a metal bit, the point angle of a masonry bit is 135° which gives them more strength. This is worth noting down especially if you are considering sharpening the masonry bit by yourself.

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The masonry drill bit is a twist bit with tungsten carbide cutting tips. A typical masonry bit has a carbon steel or HSS body and a sloping tip that is often covered in carbide. The carbide helps keep the bit sharp when punching through masonry or concrete.

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This type of wood bits are also used for drilling large holes. The advantage here is that, the radial cutting edges deliver smooth finish.

There is also the hole-saw which you can use to cut large diameter holes. So, how is this tool different from a Forstner bit? Please read this comparison between Forstner bit vs hole saw for more details.

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At first glance, most drill bits appear to be alike and all have the same purpose which is to drill a hole into tough material such as wood, masonry, metal, concrete, and others. But closer inspection shows that there are significant differences between wood and masonry drill bits or concrete bits. Using the right one for the job is paramount in getting the results that you desire.

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Another difference is the hardness as masonry bits are made from tungsten carbide which is a considerably stronger material. Many wood drill bits are made from carbon steel which will quickly dull if used on masonry or concrete.

Milling cutter size chart

These bits have close spiral body with low helix angle. It has screw tip in the center that will penetrate and pull the wood towards the bit.

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Spade bit, also known as paddle bit has a round shank and a flat blade like cutting edge. This wood bit also has a spur tip in the center, similar to the brad point bit. They are used to make large size holes.

You can see the differences in holes when using both types of bits on wood. While a masonry bit can drill into wood, it leaves a rougher, less sharp hole as compared to a wood drill bit. Conversely, trying to use a wood drill bit on masonry will result is a ruined bit early in the process. Wood drill bits are not made to punch into materials and the spurs will work against the bit from progressing cleanly into the masonry, concrete, or tile.

As I explained before the main difference between these drill bits are in the material used for making the bit and the geometry of the cutting edge.

The twist drills are widely used in metalworking; but they can also drill wood. For softwoods, you often find bits made of carbon steel is used as it provides enough hardness to go through the wood and create a clean hole. However, hardwoods can quickly dull a regular steel bit, which is why titanium-coated drill bits or cobalt bits are recommended as they last longer.

A wood drill bit is designed to rotate and drill into the wood from the start. This may seem obvious, but the same is not true of a masonry drill bit which uses rotational as well as hammering forces to punch a hole as it is drilling. The gentle sloping angle of the masonry drill bit allows it to punch into the stone materials easier where a wood drill bit would not work so well.

Wood drill bits are made of high carbon steel or high-speed steel. A brad point bit is the one that is commonly referred to as wood drill bit. But there are several other types of wood drill bits.

The easiest way to tell the difference is by looking at the cutting tip geometry. On a wood bit there will be a sharp pointed spur in the center whereas the masonry bit has a carbide tipped cutting edges that are ground to 135-degree angle.