UNF 1/4" 28G thread

It has its origin in the USA. Mainly used in chromatography/HPLC applications. Most common sizes are UNF 1/4" 28G and UNF 10 32G. The digits 28 G and 32 G stand for the number of thread pitches at a length of one inch (25.4 mm).

UNF 1/4" 28G versus M 6

Without exception all BOLA HPLC fittings come with the most common HPLC thread UNF 1/4" 28G. In addition, fittings and distributors with the very similar thread M 6 are used. These threads can only be distinguished by exact determination of their outer diameter or by using a test mandrel (it is possible to screw in a tube end fitting in the counterpart of the other thread for at least 2-3 rotations). The UNF 1/4" thread has an outer diameter of 6.35 mm, the M 6 thread has precisely 6 mm (work tolerances are possible). We recommend to use only the UNF 1/4"-28 G thread to avoid confusion and double inventory.