The subject of proper connector torque arises often, and for good cause. Failure to follow the proper specifications and recommendations for a given connector type can damage expensive equipment and degrade measurement integrity. Often times it’s not only test instrumentation and cables that fall victim to improper torquing procedures, but the deliverable hardware itself. Experienced engineers understand the importance of applying the proper torque when mating connectors, but it’s still typical to find non-torque-calibrated (traditional) open end wrenches laying about in most Engineering laboratories, and connector damage due to over-torquing remains one of the most common causes of repair costs and equipment downtime. Using a properly calibrated break-over torque wrench when tightening connectors is therefore guaranteed to save time and money.
Mini-Circuits has developed a series of break-over torque wrenches following a set of torque recommendations that we suggest for the most common microwave connectors used in our product portfolio. Note that we recommend a more conservative torque specifications than IEEE working group 287 for several of the series. Mini-Circuits’ torque recommendations, torque wrench model numbers and case styles are shown for general reference in Table 1 below.
Table 1: Recommended torque for different microwave connector types and corresponding Mini-Circuits torque wrench part numbers.
| Connector Type | Mini-Circuits* | IEEE 287-2007 | Units | Mini-Circuits Torque Wrench Part Number |
| N | 8 ± 0.32 (0.9 ± 0.04) | 13.3 ± 1.8 (1.5 ± 0.2) | In-lbs (Nm) | TRQ-N20-8 TRQ-N20.6-8 TRQ-N34-8 |
| SMA | 8 ± 0.32 (0.9 ± 0.04) | See Mfr. | In-lbs (Nm) | TRQ-516-08 |
| 3.5mm | 8 ± 0.32 (0.9 ± 0.04) | 13.3 ± 1.8 (1.5 ± 0.2) | In-lbs (Nm) | TRQ-516-08 |
| 2.92mm | 8 ± 0.32 (0.9 ± 0.04) | 7.1 ± 1.8 (0.8 ± 0.2) | In-lbs (Nm) | TRQ-516-08 |
| 2.4mm | 8 ± 0.32 (0.9 ± 0.04) | 8.0 ± 1.8 (0.9 ± 0.1) | In-lbs (Nm) | TRQ-516-08 |
| 1.85mm | 8 ± 0.32 (0.9 ± 0.04) | 8.0 ± 0.9 (0.9 ± 0.1) | In-lbs (Nm) | TRQ-516-08 |
*Mini-Circuits’ recommendation for an optimal connection when used with Mini-Circuits products. Torque recommendation may vary by connector material composition. Always consult manufacturer’s mechanical specifications before mating connectors.
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