CONFLICT BTWN A VFR DEPARTING PA46 AND AN ARR MD80 10 MI W OF CAK; OH; DUE TO AN INCORRECT ALTIMETER SETTING BY THE PA46.

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WHILE FLYING A VFR FERRY FLT FROM CAK; WE WERE INSTRUCTED TO CLB AND MAINTAIN 6500 FT. THE AUTOPLT AND PRESELECT WERE SET ACCORDINGLY. CAK DEP CALLED OUT TFC AT 'SW; 10 MI; DSNDING TO 7000 FT.' AFTER SOME MOMENTARY CONFUSION OVER THE 'SW' TERM; THE TFC WAS SIGHTED BOTH VISUALLY AND BY OUR OWN CAS SYS (BRG SKYWATCH). CLOSURE TO ABOUT 2 MI HORIZ AND 500 FT VERT OCCURRED WHEN THE MD80 CREW CALLED OUT THAT THEY WERE IN A RA CLB. CAK VERIFIED MY ALT 6500 FT AND ANNOUNCED A 500 FT SEPARATION. AS THIS TOOK PLACE; I HAD SEEN OUR AUTOPLT CONTINUE A 1000 FPM CLB THROUGH 6500 FT; THE AUTOPLT WAS IMMEDIATELY DISCONNECTED AND THE ACFT LEVELED AT 6680 FT. NO OTHER ACTIONS/COMMENTS TAKEN. I BELIEVE THAT I HAD FAILED TO RESET THE BAROMETER SETTING ON THE PRESELECTOR UNIT. THIS UNIT RESETS TO 29.92 INCHES WHEN TURNED ON. CURRENT ALTIMETER SETTING WAS 30.41 INCHES HECTOR PASCALS. OUR ALTIMETERS HAD BEEN PROPERLY SET AT 30.41 INCHES. OUR DEP WAS RUSHED AND THE AUTOPLT PRESELECT HAD NOT BEEN PROPERLY CHKED. FUTURE OPS WILL ENSURE THAT THE PRESELECT IS CHKED/XCHKED WITH THE ALTIMETERS PRIOR TO DEP.