Boston — If it's an electric guitar, a bag of fertilizer, or a jumbo jet you want, you'll be buying the best if you ''buy American.''
You also won't go wrong if you're in the market for US-made precision scientific instruments. At least the rest of the world seems to think so: American exports of those were calibrated at $1.2 billion last year, up from $ 200 million 10 years earlier.
Some other domestic products or categories considered No. 1: telecommunications equipment, home computers, calculators, pharmaceutical products, motor fuels, paper (from tissues on up), medical equipment, avionics, photographic film, pleasure boats, outboard motors, electric motors, glass, textiles, locks, and lighting. Moreover, the United States is better at packaging its products than any other country.
So say experts surveyed by the Monitor in the fields of consumer research, product testing, manufacturing standards, and quality control.
And there's more. Still other US-made items lead the market, these sources say, largely because foreign manufacturers can't afford or choose not to compete with them here - or, more likely, haven't established themselves in the field yet. Among these: electronic games and large household appliances such as refrigerators, washing machines and dryers, dishwashers, and air conditioners.
If you're getting the idea that the United States is a long way from relinquishing its status as a world leader in manufacturing, experts say, you're right.
''People think everything is being taken away from us, and it's not,'' says Chuck Carter, an internationally known quality and reliability consultant from Richardson, Texas, and author of nine books on the subject. ''It isn't that we don't know how; we just don't do it. We're lousy planners. But we're coming back.''
Others in the field are quick to agree.
Says Bill Rockwell, general counsel of the American National Standards Institute in New York: ''Quality is a very subjective thing; it's in the eye of the beholder. In some areas in this country, we've lost the will to be the best. But there's a tremendous effort on the part of industry to bring back what they lost.''
Red Binstock, director of publications for the Milwaukee-based American Society for Quality Control, adds that the US ''seems to be motivated by crisis. Now that they realize they've lost their lead, many manufacturers are beginning to fight back. Unfortunately, they've got a long row to hoe.''
But Mr. Binstock says,''There are still many American products that people trust.''
A few of them that critics say take a back seat to no one:
* Telephones. Among praises heaped on the best-known US manufacturer: ''finest in the world''; ''there just is no comparison''; ''anyone who owns a competitor wishes he didn't.''
* Calculators. Americans who travel to Japan for advice, assuming that it leads in calculator technology because it is preeminent in many electronic consumer products, are referred back home, Dr. Carter says. ''The Japanese know the Texas Instruments and Hewlett-Packards are the world leaders, and those companies are not going to let anybody take that away from them.''
* Photographic film. Frank Cricchio, vice-president of the Professional Photographers of America and a studio owner in Port Arthur, Texas, says if he had a once-in-a-lifetime assignment, like making the official color portrait of the President of the United States, he would unhesitatingly choose US-made film over that from Japan or any other competitor. American film, he says, has better dye stability than that made overseas, so prints last years longer.
* Guitars. A spokesman for Boston Music Company at Berklee, a store attached to the internationally known Berklee School of Music here, says US-made guitars - both electric and acoustical - are by far the first choice of foreign as well as American students.
* Spark plugs. The popular TV commercial in which an English-speaking Japanese garage mechanic contends that a certain American-built plug is just the thing - even for Japanese cars - is right on target, Dr. Carter says. ''We're king.''
For those who would be king, Carter advises: ''You've got to work at it 365 days a year, or you won't hack it.''