Sag 180 TDI measurements

Could some help me with the dimensions of the thread dial indicator gea and it’s thread pitch. I know I don’t need one to cut threads but I’m looking for a project to do. I can see that the feed screw is 3/8 pitch but I don’t understand what that stands for. I’ve searched the web for screw pitches and I can’t find anything that resembles a 3/8 pitch to buy a gear for the TDI. I saw on another post that the gear is a 16 tooth but there were no dimensions such as diameter and thickness etc. I found drawings for a 16 tooth 4 pitch that could work but I’d really like to understand the 3/8 pitch and make a proper sized gear. Any help would be appreciated. If someone wants the gear dimensions I found I can share them.

Thanks