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Is the slide rule now a tool only for calculating collectors?

IT'S a tool that engineers who built the Golden Gate Bridge, now 50 years old, would not have been without. Once upon a time, it was used in planning almost all buildings, bridges, tunnels, and other engineering projects. What tool, so universal a short time ago, is hardly seen anymore? The slide rule.

In recent years, it's become increasingly difficult to buy an old-fashioned slide rule. In the early '70s, electronic slide rules - better known as pocket calculators - made manual slide rules almost obsolete.

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Fifteen years ago, Hewlett-Packard came out with the HP-35 - reportedly the first small calculator to perform engineering functions. In the following years, mass production of calculators sent prices plummeting. The slide rule was almost forgotten.

Parsippany, N.J., is home to Keuffel and Esser, formerly one of the largest manufacturers of slide rules. Hank Haase, manager of sales administration and a 40-year veteran with the company, which manufactures drafting films and paper, has seen the rise and fall of the slide-rule business. During the 1960s, Keuffel and Esser produced 5,000 slide rules per month. In 1975, they produced their last slide rule. Mr. Haase says it was the Cadillac of the slide-rule industry - the ``Log Log Deci Trig,'' made of seasoned mahogany and precision engraved. During the earlier days of production, it took many craftsman to fashion one of these instruments. Haase notes that the United States Naval Academy and West Point were large users of the ``Deci Trig,'' as were mathematical engineers. Though they're no longer produced, the company still stocks around 1,200 or so and occasionally gets an order for some.

Why would anyone still want to buy a slide rule, when inexpensive calculators are so readily available? According to Haase, slide rules are better suited to some functions than are calculators. He explains that if you're doing quotations and bids, markups and markdowns, a slide rule lets you ``see down the road.'' For example, if you set your slide rule on a certain factor to determine, say, a 30 percent margin on the sale of your pet rocks, at a glance you can see what price you would have to charge for a 45 percent margin. This is not possible on a calculator, where you need to make a new mathematical calculation to find the figure for the 45 percent margin. Despite this isolated advantage over the calculator, Haase does not expect the slide rule to make a comeback.

Neither does Arthur Orans of Philomath, Ore. Nostlalgia and genuine appreciation for this relic of our recent past led him to found the Philomath International Slide Rule Society. Begun in 1983 after he found an ``orphan'' slide rule at a flea market, his organization now boasts more than 400 members worldwide. Periodic newsletters are sent to members, and the society maintains manuals for slide rules with special uses - such as those for chemical, integral, and naval engineering. Many sympathetic to his cause have sent slide rules to Mr. Oran - from high-tech to big classroom models. In turn, he has donated many of these ``specimens'' to the Oregon Museum of Science and Industry in Portland. For a $7 membership fee, one can join up with fellow slide-rule enthusiasts.

The mention of slide rules evokes a poignant memory for Mark Schuster, an assistant professor at the Massachusetts Institute of Technology. He remembers the giant, six-foot-long slide rules hanging over the classroom chalk boards during his student days at MIT. He says he laments the passing of the slide rule because students have lost the ability to estimate in a creative way. With slide rules, the user has to figure out the correct placement of the decimal points. Students are now using calculators or computers to solve complex mathematical problems. Their tendency is to simply trust the answer their calculator has given them without thinking about whether or not the answer is reasonable.

Although it seems that everyone has become accustomed to the decimal points and push-button ease of calculators, most of those contacted for this article do not believe that slide rules are collectors items. But who would have thought that Superman comic books - or even the Ford Edsel - would become collectors items?

Philomath International Slide Rule Society, Box 892, Philomath, Ore. 97370.