This Term is a way of Describing the Threading on a Fitting so that it will properly be Matched to a receiving Port such as a Column Connector and a Column. This Match is important for a good Seal and long life of Fittings. Improper Matches will cause the Fittings to Cross Thread and wear out Prematurely.
The 10-32 Description can be broken down into two parts. The First Part (10 in this case) Describes the Diameter of the Threaded part of the Fitting. If you were to measure the Width of the Threads from side to side, this distance would be the first part.
For fittings larger than ¼” you would state the actual Measurement. For example, if it were ¼” you would state ¼ . When the measurement is below ¼”, and for English measurements and not metric, you would report his number in gauge. In this case, we state 10 gauge.
The Second Number or Part is number of Threads per unit of Distance. For our purposes, it is reported in Threads per Inch. This means that there would be 32 Threads per inch.