There are two types of mortar rake: fluted or gritted.
Fluted mortar rakes are designed to cut away sections of mortar and gritted mortar rakes are designed to grind away sections of mortar.
Most mortar rakes are made out of steel. The cutting/grinding section is usually made from solid tungsten carbide or coated with a diamond or tungsten carbide layer.
Fluted mortar rakes
Fluted mortar rakes are designed to cut through mortar; the flutes acting as blades slicing through mortar.
You can buy fluted mortar rakes that need to be screwed into a collet (or adaptor) that in turn screws onto an angle grinder spindle.
Just the fluted section is also available. This goes into the collet which in turn goes onto an angle grinder spindle.
Fluted mortar rakes with a solid shank are designed for drills. These tend to be made out of steel with a tungsten carbide coating.
Gritted mortar rakes
Gritted mortar rakes are designed to grind through mortar; the granules rubbing down the mortar.
There are a variety of mortar rakes available with different types of grit covering.
You can purchase gritted mortar rakes that can be screwed onto an angle grinder spindle.
Some gritted mortar rakes need to be attached onto an adaptor that in turn is inserted into an SDS plus drill.
Mortar rakes coated with diamond tend to be gritted mortar rakes. However, there are also fluted mortar rakes available that have diamond set onto the blades of the flutes.
Diamond is used as a coating for many mortar rakes because it is extremely hard wearing and strong. It will have a longer life span than tungsten carbide products, however, it will also be more expensive. Due to its strength, diamond wears down mortar very quickly and efficiently.
Both gritted and fluted mortar rakes are available coated with tungsten carbide. You can also buy solid tungsten carbide fluted mortar rakes.
Like diamond, tungsten carbide is extremely strong and can take a lot of wear and tear. As a result, some would recommend using this on tough Portland cement based mortar only. Because it is not as strong or as rare as diamond, tungsten carbide bits are cheaper to buy.