Grinder with features to help move ground substances

A grinder, comprising:

• a first grinding section comprising a first inner surface;
• a second grinding section configured to couple to the first grinding section, wherein the second grinding section comprises a second inner surface and a sidewall extending from the second inner surface to define a receptacle configured to receive a substance, wherein a plurality of holes is formed through the sidewall to enable the substance to pass through the second grinding section;
• and
• a plurality of bumps extending from at least one of the first inner surface or the second inner surface, wherein the first grinding section and the second grinding section are configured to rotate relative to one another to cause the plurality of bumps to grind the substance disposed in the receptacle.