UNEF thread gage stands for Unified Extra Fine thread gage. Measuring wires, tri-roll comparators, thread rings gages, thread plug gages, thread micrometers are some of the various thread gaging instruments. The various aspects to consider while selecting a suitable variable and fixed limit gage for an application are internal and external thread type of an application, particular designation of a thread like UNS, UNF, UNC, UNEF, NPT, ACME, or buttress, part tolerance, and gaging frequency.
In case of UNEF thread gage, the TPI which stands for Thread Per Inch is a measure for threaded fasteners and woven fabrics and is a number of threads per inch of fabric are big. The more the TPI, the finer the thread is and for UNEF thread gage, TPI is usually 18,20,24,28,32. UNEF, the extra-fine-thread-series is appropriate for situations where finer pitches of threads are suggested. Considering the conditions like a short length of engagement, or the thin-walled tubes, nuts, ferrules, and couplings the UNEP is the most suited thread gage.
UNEP thread gage is made of oil tool steel which is hardened, drawn, and stabilized. These features of oil tool steel equip the UNEP thread gage with properties like wear resistance, anti-friction, stability to distortion. These gages are available in various designs including the reversible design, taper lock design, and the tri-lock design. The advantage of the reversible design is that it permits the rotation of one end of the gage allowing the user to get two gages in one. In such design, if one gage gets worn out the other end becomes the new gage. The user simply needs to open the collet of handle, turn the thread plug gage and brush around, and the opposite end is the new gage. The advantage of taper lock design is that it allows the easy replacement of worn out end of gage by insertion of the new end of the gage into the handle through press fitting. These taper lock gages render the drastic savings to replacement cost. The wear life of taper lock thread gages is extended to more than 100% by stocking them in chrome coating. The advantage of Tri-lock gages is that they are available in reversible style and enables the use of both ends of the gage.
UNF thread gage is one of the designations of the series, which stands for Unified Fine wire. UNF tells the number of Thread Per Inch (TPI), the standardization which depends upon the Gauge. The fine, extra fine and course series were established to improve the size standardization and to ease the design. So, if the requirement of the design is a finer thread than the first, the nominal major diameter is picked proceeding to the identification of fine thread for that size within the standard, and finally, this thread is used in the design. Inch sizes come in UNF and are used to specify the fastener diameter. In the case of small fastener, the UNF is 4-48 or 8-36, and in the case of the large fastener, the UNF is ¼-28.