THEY USE so much thread at Sugarbush that they put it right in their logo: "The Thread Fairy."

Thread cones are all over the place: hitched by sixes to a sewing machine, stacked on shelves, still packed in their boxes. The best cotton thread. $9.46 per cone of 6,000 yards. They use 10 a week.

That's 34 miles a week. In a year they could stitch up the highway from here to Denver.

"I save all the used cores. I'm going to build a castle with them someday," says the founding designer and manufacturer, Susan Bush. She lives amid the backpacks, the purses and tote bags and wallets, the piles of cut fabric, and straps, and belts, and zippers, and linings, and thread cones. And they talk. All the time. In red, green, blue, orange, brown, black, tan.

They don't shout, but you definitely hear them, day and night, breakfast and dinner. In the living room, the dining room, the halls, all through the apartment, a high-ceilinged old charmer on Columbia Road. She always works in those seven strong colors. "They pick up almost any color you could wear. Look at this with pink."

She holds up a blue-green-red handbag with abstract grass spears on it. Very nice. It is talking politely and quite distinctly.

"At first I couldn't stand it, working and living in the same place. Start to do the dishes and then see some swatches you had to move. But I've matured. You learn to draw lines."

Actually, she's a pianist. Studied 18 years in her native Denver, once played First Piano in a 200-piano extravaganza. Books by Walter Piston on the shelf. She is 32.

"I didn't want to be a music teacher and beatSee SUGARBUSH, Page 3, Col. 1 SUGARBUSH, From Page 1 on kids' backs," she says. "I'd been making a few rather elaborate things, dresses, smoking jackets with special little pipe pockets and pockets where you could put individual cigarettes under a little flap. It was a labor of love but not a very sensible way to live. Then four years ago I started seriously turning out fashion accessories."

Sugarbush has doubled its income every year. There are now 11 canvas products, soon will be 12. She thinks about a major expansion but hates the hard, mean world of the big-time garment trade, where a rival will casually steal your purse to copy it if you take your eyes off it when he's in the same room with you. She goes to the trade shows for the wholesale market in American crafts, gets orders from all around the country, from Neiman-Marcus, from tiny museum shops. There is an account in Japan, which pleases her.

"The backpack is the cornerstone of the business. We make 100 bags a week. A lot of professional women are using backpacks but they're attracted to color and don't want just those ones you get in the sports stores. These are more casual."

Fashion-conscious customers also go for the matched sets: the carry-on bag and purse, the tote-bag and pack. Bush gets a kick out of demonstrating the carry-on bag. Its sheer ingenuity is delightful: outside pockets, inside hideaways, zippered pouches, a place for your magazine, a handle that turns into a shoulder strap. All triple-stitched and bound, unusual in a canvas bag.

"I developed this one. It has a stiff plastic bottom, stands alone, has nickel reinforcement strips at the top. It sells like crazy."

The bags are hung from wall racks, dominating the living room as though it hadn't already been taken over by sewing machines, cloth strips, steam irons, drawings, account books and the famous thread. There are two full-time workers and "a parade of part-time people" who show up for the Christmas rush.

"People are always saying how neat it must be to have my own business, but they don't know about those 18-hour days and working through the night. I've cut it down a bit as I learn how to do things, but if it were simply the money I could never have done it. It has to be interesting."

Interesting. The trademark war was interesting. For four years she fought a big shirt company with seven factories and platoons of lawyers. She won.

Sometimes she regrets turning her back on the piano. But then a new idea flares up, a problem in design, a decision. A circular purse. Hmm. Wasteful to cut. Hard to sew. And it would look like a Frisbee case. But you could have this flap come out, see, and a zippered cardcase pocket here, and it would all fold into this smashing round shape. Hmm.

And in orange, red and green, it would speak for itself.