Weakened demand for hand tools and industrial products reduced earnings for the fourth quarter and year at Easco Corp., a Baltimore-based toolmaker and metals producer. Another Baltimore company, Fair Lanes Inc., reported a sharp jump in profits from its bowling-lane operations.

Easco said earnings in the fourth quarter dropped 52 percent to $1.3 million (31 cents a share) from $2.7 million (79 cents), a year earlier. Revenues in the period, however, were up 8 percent to $105.7 million from $98.1 million.

For the year ended Dec. 31, Easco earnings fell 8 percent to $10.8 million ($2.81) from $11.8 million ($3.50) in 1981. Revenues in the year rose 3 percent to $426 million from $415 million.

Fair Lanes, which operates 89 bowling centers in 20 states, said it earned $2.1 million (39 cents) in its second fiscal quarter, up 26 percent from earnings of $1.7 million (31 cents) a year previous. Revenues increased 5 percent in the quarter, to $20.7 million from $19.7 million.

The company reported a 52 percent increase in earnings in its first half ended Dec. 31, to $2.3 million (43 cents) from $1.8 million (33 cents) a year earlier. Revenues rose 6 percent in the half, to $36.5 million from $34.4 million. The half included the sale of five Treadway Inns that added $287,000 (5 cents) to earnings.