bgagnon created the topic: How to properly torque a right angle SMA connector

I have noticed that while playing with a right angle SMA connector that the resulting breaking torque varies which different matting techniques given the same setting on the torque wrench. There were two scenarios that I was interested in.

1. ) I finger tighten the right angle SMA connector on my RF cable. The mating connector is fixed to the table. Then, using an 8 inch pound torque wrench I tighten the connector WHILE preventing the connector body to rotate. The only part rotating is the coupling nut. I use my other hand to prevent the connector body to rotate. This keeps the cable in the same spot.

2.) I finger tighten the right angle SMA connector on my RF cable. The mating connector is fixed to the table. Then, using an 8 inch pound torque wrench I tighten the connector WHILE NOT preventing the connector body to rotate. The connector body rotates with the coupling nut and the cable ends up a number of degrees rotated from where it initially was.

After measuring the breaking torque on these mates on a relatively large sample set (each scenarios was performed 25 times), scenarios #1 results in about half as less breaking torque which is bad. ~3in-lbs versus ~6in-lbs in scenario #2. Breaking torque is measured with a dial torque wrench.

My question is: What is the correct way to tighten the connector? Is there a preferred method? Does anyone know or have insight to the phenomenon that causes less breaking torque?

My current theory is that there is extra running torque between the coupling nut and connector body when you hold the cable in place. This extra torque then detracts from the resultant pre-load making the breaking torque lower. I haven't been able to find anything on this. Would be helpful if anyone has thought about this before. I can make up a graphic to explain better if needed.