As far as i know you ll usually find either ceramic or steel burrs.
Ceramic burrs vs steel burrs.
Ceramic burrs are more brittle than steel so you could chip the ceramic burr if a very hard rock was hiding in the beans.
Heat is an important factor when it comes to coffee grinder burrs because any extra heat impacts your coffee s flavor since it burns off some oils present on the beans.
Steel burrs though usually stainless steel can still corrode depending on the type of steel used.
Stainless steel burr grinders typically make it through 500 to 1 000 pounds of coffee.
In general for most people brewing at home i d say that steel burrs are better.
Ceramic burrs run a little cooler than steel burrs and there are some coffee experts who think the extra heat burns off some of the oils and impacts the flavor of the coffee.
Specifically ceramic burr grinders usually last through 1 000 to 1 500 pounds of coffee.
Ceramic burrs are molded so in order to get a high quality ceramic burr you have to a very high quality and very expensive mold.
The burrs heat up during the grinding process and this heat tends to change the taste of the ground coffee.
I haven t noticed this myself and i m not sure the argument would even apply to hand grinding.
Ceramic burrs are harder than steel and last on average about twice as long as steel burrs.
And from what i have heard from people out there.
Baratza rates theirs for 750 pounds of coffee but reports indicate that they may be good for up to 2500 pounds.
Ceramic burrs advantages.
Since ceramic and steel burrs have different heat conducting abilities.
Where as you typically want a harder steel for mills you also want something corrosive resistant but often a compromise needs to be made between one of the other.
That s not because steel is inherently better than ceramic but because of the manufacturing process surrounding them.
The lifespan of a burr grinder depends on its quality and the burr material.
Ceramic burrs transfer less heat compared to steel ones this means that the type of burr used can affect the taste of coffee.
In general ceramic burrs tend to last longer than stainless steel burrs.
Ceramic burr are less thermally conductive than steel this means these burrs transfer less heat than steel burrs see below on heat.
Last twice as long as steel burrs before requiring replacement.
First off ceramic burrs run a bit cooler compared to steel burrs or in other words they don t heat up as fast or retain heat as much as their metal counterparts.
The lifespan is about half the time per pound of coffee as the ceramics but most can be replaced.