Bottom face processing method of pillar-shaped honeycomb structure, manufacturing method of fired honeycomb structure, and manufacturing method of joined body

A bottom face processing method of a pillar-shaped honeycomb structure comprising steps of:

• preparing a pillar-shaped honeycomb structure including
• a plurality of first cells which extend in parallel with each other from a first bottom face to a second bottom face, and each of which is opened in the first bottom face and has a plugged portion having a protruding portion in the second bottom face, and
• a plurality of second cells each of which is adjacent to at least one of the first cells with a partition wall interposed therebetween, which extend in parallel with each other from the first bottom face to the second bottom face, and each of which has a plugged portion having a protruding portion in the first bottom face, and is opened in the second bottom face;
• and
• removing the protruding portion from the plugged portion of each of the first cells and the second cells of the pillar-shaped honeycomb structure without the first bottom face and the second bottom face being masked, and
• wherein the step of removing the protruding comprises bringing a plurality of brush bristles into contact with the protruding portion of each of the first bottom face and the second bottom face while rotating at least one rotary brush which includes a base which is rotatable around a rotational axis, and the brush bristles implanted to a surface of the base, and whose rotational axis is parallel with the extending direction of the first cells and the second cells.