David Smith (1906-1965) called his art "the best damned sculpture in America." Today the world agrees. Above all other Americans, Smith helped change the course of modern sculpture by adding the techniques of welded metal to a tradition limited to modeled clay, cast bronze and carved wood and stone. He paved the way for a whole new look in three-dimensional art.

Next week the National Gallery of Art and the Hirshhorn Museum join forces for the largest, most comprehensive survey of Smith's work ever assembled. The National Gallery will exhibit the seven giant sculptural series for which Smith is best known, from the early "Agricolas" (made from farm machinery), to the burnished steel "Cubis," under way at the time of his fatal car crash.

The Hirshhorn show examines Smith's little-known interest in other media: spray paintings, thickly impastoed landscapes, pen-and-ink drawings, prints, photographs and ceramics. Also included are some of Smith's personal papers, letters, sketchbooks and photographs lent by the Archives of American Art. Among the intriguing tidbits is a poignant response from Smith to a lecture request: "I wish my work was sufficient in itself, but people pay for talking where they cannot for the work."

There is also a 1947 letter to Smith from his dealer, Marian Willard:

"Dear David, In September a little guy came in to see your work . . . and selected 3 medallions and made an offer of $600 for the lot . . . I told him that I was not accustomed to reduced prices without consulting the artists . . . Let me know your feeling as soon as possible . . . Name Joseph H. Hirshhorner (sic)"

Those works were the first of 32 later acquired by Hirshhorn and given to the museum. Several are in the Hirshhorn show (Nov. 4 to Jan. 2, 1983). The National Gallery show runs from Nov. 7 to April 24, 1983.