Inserts are popular within the machining world for their ability to be replaced while using the same tooling, making them indexable.
Carbide Inserts make up over 90% of all inserts (if not 95%) and are widely used across all insert styles. Carbide is about twice as heavy as steel, having a dark gray and almost black appearance when uncoated. Carbide is popular for its wear resistance and toughness, as well as its ability to be manufactured into many shapes. Inserts should be assumed carbide unless weight or labeling suggests otherwise.
Cermet inserts are made up of both ceramic and metallic materials and will weigh less than carbide, but more than ceramic inserts. They may be colored similarly to carbide and more often uncoated. Brands to look out for are Kyocera & Sumitomo who are well known for making inserts of this material.
Ceramic inserts are made up only non metallic materials and will weigh the least of any material. They may be nearly any color, but are most often brighter than carbide, and nearly always uncoated. Brands to look out for are Kyocera & Sumitomo who are well known for making inserts of this material.
HSS (High Speed Steel):
HSS Inserts will be about 1/2 the weight of carbide and will be less resistant to wear. They will be a much lighter color and are far less common than carbide inserts. This material will likely be labeled on the insert packaging.
TiN (Titanium Nitride)
TiN is the most common coating, and can be used for many applications. It increases wear and deformation resistance and will have a golden color.
TiCN (Titanium Carbonitride)
TiCN coatings are even more wear resistant than TiN. They may be hard to differentiate from uncoated carbide, but they may have a shinier silver look to them, and TiCN will often be noted on the labeling as it is not very common.
There are other coating options that are even less common, such as TiAlN (Titanium Aluminum Nitride) and various oxide coatings.
Size / Labeling
Inserts come in many shapes & sizes and are used for a wide variety of applications. The most common type, turning inserts, will often be in the form of 4 letters followed by 3 numbers. Some examples of common turning inserts are: CNMG 432, VNMG 331, SCMT 543. This describes most of the inserts properties, which can be explained in the link: https://www.machiningcloud.com/wp-content/uploads/.... Insert labeling will not always be in this format, and there are many letters & numbers that will need evaluated for their importance.
The above images are examples of where Size / Labeling can be found on a pack of inserts. As you can see, many inserts have to separate ways of describing the insert (TNMG 160408 & TNMG 332) which are both important and need mentioned.
The grade of an insert helps determine which material it was designed to cut. Insert grades are often printed directly on the inserts themselves, as well as found on the case typically following the Size / Labeling.
As previously mentioned, turning inserts are the most common and will have some of the simplest shapes. If your Size / Labeling is in the 4 letters & 3 numbers format there is a very high chance that the insert is turning. They often have larger cutting surface area and the simplest shapes / patterns.
Grooving inserts will have a much smaller cutting edge than turning inserts, and will tend to be longer and a more rectangular shape.
Spade drilling inserts look unique, having at least 1 through hole for holding. They are far larger than most inserts and will often come in 1-2 piece packs.
Milling inserts tend to have an upward slope toward the cutting edge, and may look quite similar to turning inserts. How these inserts are named has similarities to turning inserts, but are not exactly the same. You can see more of how they are labeled here: https://www.qtstools.com/document_library/tech-res...
Threading inserts are designed to make threads (such as those on nuts) and will nearly always have a 60 degree cutting edge shaped as a V as this is the standard thread in the US.