During Commencement week, staffers of Harvard's purchasing office do not spend much time conjuring up visions of sentimental alumni strolling through the Yard reminiscing about freshman year. For them, the week's events consist of securing such items as 50,000 folding chairs for Commencement and luncheons and 18,000 towels for visiting alumni.

The array of requests from the Associated Harvard Alumni (AHA), combined with the preparations of a Commencement Planning Task Force of Buildings and Grounds (B&G) and Harvard police reveal the extent to which Commencement has become a curious combination of slick, big-business organization and small-scale purchasing.

The purchasing office takes its largest orders from the AHA, which organizes the mammoth 25th reunion and the smaller 50th, 35th and tenth reunion celebrations.

Of the $500.000 budget for the reunions, $190.000 goes for food and catering, $94.000 for housing and linens, and another $41.000 for liquor, soft drinks, glasses, and bartenders' salaries.

Other goods and services AHA rents or purchases are:

I40 tents for shelter at outside events

I17,000 bedsheets for the alumni and their families:

Iten wheelchairs, two ambulances and two stretchers in case any alumni need emergency medical care:

Ithree pianos for recitals: and.

Ithree electric fans to cool down a reception in the Radcliffe Yard.

"It's almost a 'no-frills' reunion." Marian R. Briefer, AHA associate for major reunions, said last week, adding that the 25th reunion committee has cut back on high-priced extras such as ornate centerpieces for tables this year.

The bill for hard liquor has also decreased because more people are drinking wine than in previous years. Briefer said.

These cuts and the $400 fee alumni pay to bring their families help offset the rising cost of labor and steep price increases for large events. For example, the cost of renting Symphony Hall for the traditional Boston Pops concert for alumni and their families "goes up in the thousands" each year, she said.

Despite these cutbacks, the half-million-dollar budget still allows AHA to spend $14.000 for the salaries of 100 counselors employed to supervise the children's activities and $15,000 for one luncheon. AHA also purchases $37,000 worth of "gifts" for the alumni and their families. These include umbrellas, frisbees, and wastebaskets, all of which bear prominent renderings of the crimson insignia of the Class of '56.

Rather than spend money during Commencement week, the class of 1981 will probably make a profit by charging admission fees to its events. Diane Dussault, administrative assistant for AHA said last week, adding that unlike the 25th reunion activities, many of the events sponsored by the senior class committee have cash bars. The senior class dance, for instance. turned a profit of $650 by selling $100 worth of liquor. The profits from the Class of '81 events will go into a class treasury.