NMAC BTWN 2 SMA SEL ACFT IN AN UNCTLED TFC PATTERN DURING TURN TO FINAL.

Narrative

I WAS MAKING TOUCH AND GO'S AT THE PINEDALE ARPT AND HAD BEEN IN THE PATTERN FOR APPROX 25 MIN. I WAS IN THE PROCESS OF COMPLETING MY 5TH AND FINAL LNDG. I WAS APPROX 1 1/4 MI OUT ON A L HAND DOWNWIND TO RWY 29 AT 8200 FT AND HAD ANNOUNCED TO UNICOM AND TFC ON 122.8 MY POSITIONS AT ALL TIMES. I HAD JUST THROTTLED BACK AND SLOWED DOWN THE PLANE AND PREPARED IT FOR LNDG. I HAD ANNOUNCED THAT I WAS TURNING L BASE FOR RWY 29 AND A FULL STOP LNDG. I STARTED A L DSNDING TURN AND WAS APPROX 20 SECONDS INTO IT WHEN A SMALL LIGHT PLANE FLEW UNDER MY ACFT MISSING ME BY ONLY A FEW FT. I MADE A R HAND 360 DEG TURN AND RE- ENTERED THE PATTERN AND ANNOUNCED MY INTENTIONS AND LANDED ON RWY 29. THE DAY WAS CLR; UNRESTRICTED VISIBILITY AND WITH RADIO TFC IN THE AREA. THE PINEDALE ARPT HAS SEVERAL STUDENTS AND LOW HR PLTS IN TRAINING AND PRACTICING AT ALL HRS OF THE DAY. THE LCL PLTS ARE AWARE OF THIS SIT AND ARE VERY CONSCIOUS OF THE IMPORTANCE OF ANNOUNCING THEIR POSITIONS IN THE AREA AND THE TFC PATTERN. MR. X IS AWARE OF THIS AND BY NOT DOING SO I BELIEVE; THIS IS A VIOLATION OF RECKLESS AND CARELESS OP OF AN ACFT.