It is not the hosel bore depth that affects the finished club length. It’s the measurement from the bottom of the bore to the ground line that affects the final club length measurement. If a bottom of bore to ground line measures 1″ and you are assembling an iron to 38″ the cut shaft length would have to be 37″. To measure the bottom of bore to ground line insert a shaft into each iron head and measure the club for length just as you would measure any club for length. Say the shaft measures 39″ raw length and when inserted into the club the club measures 40.25″. The 1.25″ difference is the bottom of bore to ground line measurement. If you were assembling to 38″ finished length in this case your cut shaft length would be 36.75″.