A standard element required for the manufacture of a Printed Circuit Board is a drill drawing table, also known as a drill table or a drill drawing legend. The drill table lists the size and number of holes for each drill used on the board. Each drill size can be represented by a symbol, a letter, or the actual hole size. The Drill Table is configured in the Drill Table dialog, with the assignment of symbols / letters to hole sizes being performed here.
The drill symbols are always configured in the Drill Symbols dialog and the assignments remain consistent for a PCB. The dialog can be configured from a variety of places; generally you will find access to it where you need it.
Specifically, the Drill Symbols dialog can be accessed via:
The grid area displays detailed information about the mapping of a symbol to a hole size. It can be customized, including:
Click the Grouping button to set which properties are to be used to control the assignment of symbol-to-drill events (holes). Holes are clustered initially by hole size and then assigned separate symbols whenever a grouping option that uniquely identifies them is enabled. For example, the design could include a round pad with a 1mm hole, and another square pad with a 1mm hole - if Pad Shape is not enabled in Grouping, then they will be assigned the same symbol. But if Pad Shape is enabled in Grouping then they will be assigned separate symbols.
Each hole site can be represented by a symbol, a letter, or a string showing the actual hole size. These options control the symbol style and size:
These options control the style of drill symbol and when they should be shown:
There is a total of 15 symbols available, as shown below. If there are more than 15 different hole sizes in the PCB then letters are automatically assigned.