BOSTON (AP) _ Every weekday, almost 300 employees of the world's largest razor blade manufacturer come to work unshaven.

At an appointed time, the men take their place in a row of 28 cubicles, apply shaving cream to their faces and become part of Gillette Co.'s never- ending search for a better blade.

Their daily shaving ritual is often watched by experts who record the number of strokes, the time spent shaving and other factors. Sometimes, the experts even collect the stubble in jars for examination.

For Gillette, the behemoth of the blade business, razor research means big bucks and security that looks almost as tight as some military installations.

''You can imagine that the leader in any market would also be the leader in research and development,'' said Gillette spokesman Greg Niblett. ''We're always looking for how to get a better shave.''

Gillette spent $61.9 million last year on research for all its products. Though it won't release a figure on shaving research, Niblett said ''a good percentage of that is spent on blade and razor development.''

And for good reason: Gillette, which pioneered the disposable blade at the turn of the century, sells 60 percent of the 2 billion blades bought each year in the United States. It's an edge the Boston-based company does not want to lose.

The employees volunteer to shave at work, usually during work hours, at the 27-acre complex, which turns out about 5.4 million blades a day.

The men, who range from production workers to department managers, take their place in a long row of booths, each equipped with a mirror and sink. A test center employee hands them shaving cream and a razor through a window, and, in undershirts or bare-chested, they go to work.

Afterward, the men check off boxes on a computer card to rate their shave according to smoothness, closeness, freedom from nicks and cuts, and overall comfort.

The men never know what they are testing. It could be an experimental blade, an existing Gillette product or one made by a competitor.

The center has been in operation since 1973, and some of the men have tested razors for years. They receive no additional pay, though they often are given gift certificates or movie passes.

''Basically it's very convenient for me to shave here,'' said Gary Zakrzewski, a manager in Gillette's product evaluation division who has shaved at work every weekday morning for 21/2 years.

''It does save some time in the morning at home. And the other thing is I'm kind of interested in the type of products we make, to judge the quality of what we shave test.''

The testers' evaluations are fed into a computer along with evaluations from 2,400 Gillette employees, family members and friends nationwide who test razors at home.

''Shaving is a very, very subjective process,'' Niblett said. ''We all have different beards.''

That leads to widely differing opinions among the blade testers as to what constitutes a good razor.

''Eventually you're going strike a balance that pleases a majority,'' he said.

Gillette's razor research has several goals.

''On one hand, we're trying to determine whether new products meet performance and safety standards,'' Niblett said. Another goal is to test the quality of existing products.

''It's one thing to produce a good blade. It's another thing to produce it a million times over,'' he said.