Portable motor-driven cutter

A portable motor-driven cutter for cutting off a sheet material, comprising:

• a motor housing accommodating an electric motor therein and doubling as a grip handle, said motor housing extending substantially in a direction in which said cutter is moved to cut off a sheet material;
• a gear case fixedly mounted on one end of said motor housing;
• a gear cover attached to said gear case;
• an eccentric shaft rotatably supported by said gear case and said gear cover and extending substantially horizontally and transversely to said direction, said eccentric shaft including an eccentric portion;
• a gear mechanism disposed in said gear case for transmitting rotative power from said motor to said eccentric shaft;
• a substantially L-shaped driver arm including a substantially vertical arm member having a vertically elongate slot and a substantially horizontal arm member serving as a blade attachment base, said vertical arm member having an upper end rotatably fitted over said eccentric portion of said eccentric shaft;
• a guide pin supported by said gear case and said gear cover below said eccentric shaft and extending through said slot;
• a base attached to a lower end of said gear case and having a hole elongate in said direction;
• a cutting blade detachably mounted on said blade attachment base and projecting through said hole below said base;
• and
• a scribing blade detachably mounted on said base and having a lower end projecting slightly from said hole.