Making and enjoying craft stuff is, in most of this great country, a conservative, safe, grandma-and-the-kids-type activity. Behold the Jo-Ann craft megastores dotting the nation, straining under the weight of "silk" flowers and stickers featuring geese ´n' gingham. The American Craft Show will probably include some of the usual Bay Area response to such uninspired do-it-yourselfing: skillful basketry, ceramics, and wearable art. But it will also feature something unusual, even for a left-coast crafts fair: the Crucible's Educational Response Vehicle. This lovingly restored 1960 International Harvester fire truck contains a full metal shop, and the friendly freaks who drive it perform demonstrations of glass flameworking, welding, and other activities grandma might not set up on the kitchen table. True to the mission of the Oakland "fire arts" education center, such activities delight the small-fry and make everyone else itch to hold a blowtorch.