How to Clean a Coffee Grinder
If you want to clean your coffee grinder, start by pouring 1/4 cup of white rice into the grinder. Next, turn on the grinder and let it grind the rice for up to 1 minute, which will soak up any oil or residue in the machine. When you're done, throw the rice flour into the trash, wipe down the inside of your grinder with a damp paper towel, and let it dry before you use it again.
Measure ¼ cup (59 ml) of uncooked white rice into the grinder. Buy a package of white rice at your local grocery store, or use rice that you already have on hand. Make sure to use white rice for cleaning purposes. Use ¼ cup (59 ml) to ⅓ cup (79 ml) depending on the size of your grinder. Measure the rice and pour it into the grinder. Run the grinder for about 1 minute. Plug the grinder in and turn on the power. Turn on the blade and let it grind the rice for at least 30 seconds and up to one minute. This will turn the rice into rice flour. The rice cleans the grinder by soaking up oils and residue left in the grinder by coffee beans. Dump the rice flour out. Shut the grinder off and unplug it. If your grinder has a detachable hopper, take it off of the base. If not, take the whole grinder to the trash can. Dump the rice flour into the trash can. Even if you use rice flour on a regular basis, don't use this flour because it is contaminated with old coffee residue. Wipe the grinder down with a damp cloth. Get a paper towel barely damp with warm water. Carefully wipe down the inside of the grinder. Get all of the crevices. Be sure not to cut yourself on the blades as you wipe down the grinder. Rinse the paper towel and wipe the grinder more than once if necessary. Be careful not to get the grinder soaking wet, as some of the moisture could stay inside it. Get the cloth just wet enough to wipe up the remaining flour. Allow the grinder to dry. Never use your grinder for coffee beans when it is still wet from cleaning. Dry it off with a cloth and allow it to air dry completely before you use it again. It may be helpful to dry the grinder upside down to make sure no moisture settles into it. Vacuum or blow air inside the grinder. Use a vacuum that has a wand attachment to clean out your grinder. Unplug the grinder and set the vacuum up close to it. Poke the wand around the inside of the hopper and around the burrs to remove as much of the coffee dust as possible. If your vacuum has multiple attachments, use the one with the narrowest end that will help you get the nooks and crannies of the grinder. If you want, use a can of compressed air to blow dust out of the grinder instead of sucking it out with a vacuum. If you are in a hurry, or don't have a vacuum or compressed air handy, blow in the grinder a few times to dislodge any leftover grounds. Be careful not to blow anything into your eyes. Remove the hopper and wash it by hand. If your grinder has a removable hopper where you load the beans, take this off and wash it separately. Wash the hopper and lid by hand with warm soapy water. Make sure you rinse it thoroughly to get all of the soap residue off of it before you use it again. Allow the hopper to air dry upside down. If you are in a hurry, dry it with a lint free cloth or a paper towel. Take one of the burrs out. On most coffee grinders, either the inner or outer burr can be removed. It may require a tool that came with your grinder. Check the manual to find out how to remove the burr. Take out whichever one comes out most easily. If neither one comes out easily, you'll have to clean them while they are in the grinder. Be careful using tools to take the burr out. Make sure the grinder is unplugged for safe cleaning. Scrub the burrs with a toothbrush. Use a toothbrush or brush made for coffee grinders to carefully scrub all parts of the burrs. Scrub the one you've taken out first and then scrub the burr that is still in the grinder. Get all the cracks and crevices of the burrs, anywhere you can reach with the brush. Use a brush with stiff bristles, but make sure they are not metal. Metal bristles may damage the burrs. Tip the grinder over and shake grounds out into the trash. After you have scrubbed the burr in the grinder, dump loose grounds into the trash. Scrub again and dump it out again if any more grounds seem to be stuck in there. Repeat this process as necessary. Wipe inside the grinder with a dry rag. Take a dry, clean wash cloth and wipe all parts of the grinder where the beans go. Wipe the burrs themselves carefully, and also wipe the chute and catcher where the coffee grounds fall. The “dry” cloth is important. Never use a damp rag to clean the grinder. The metal parts will corrode if moisture gets into them. 
Measure ¼ cup (59 ml) of uncooked white rice into the grinder. Run the grinder for about 1 minute. Dump the rice flour out. Wipe the grinder down with a damp cloth. Allow the grinder to dry. Vacuum or blow air inside the grinder. Remove the hopper and wash it by hand. Take one of the burrs out. Scrub the burrs with a toothbrush. Tip the grinder over and shake grounds out into the trash. Wipe inside the grinder with a dry rag. 