Electronics > Beginners
Loose Crimp Sleeve (Outer Ferrule) on BNC Ferrule after Crimping [RG-58]
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rstor22:
I found that the BNC center pin once inserted into a BNC connector clicks and locks in place and does not come out (for some RG-58 connectors). After crimping the center pin and the outer ferrule (crimp sleeve) and pulling to test the crimp everything seemed fine. On some of the crimps I have made I found that the outer ferrule did not crimp securely and pulling to test the BNC connection gave a false sense of security as it appears that the crimped center pin prevented the BNC connector from detaching from the cable (since the center pin is also crimped to the core of the cable).

I decided to do some more tests and crimped some outer ferrules (using an Xcelite ratcheting crimper) on the BNC connector (with no RG-58 cable / pin) and found that for some BNC connectors the outer ferrule just slides off after pulling slightly. I tried some unknown brands along with named brand Amphenol BNC with disappointing results. I found that I needed to adjust the tension dial to a higher tension on my crimp tool for the unknown brand BNC connector outer ferrule to crimp satisfactory to the BNC connector (though it needed A LOT of force for the ratcheting mechanism to disengage at that setting). Some other brands such as Provo BNC connectors had their outer ferrule crimped successfully at the lowest tension setting and seemed to be sturdy when pull testing by hand.

Today I had a colleague of mine who crimps RG-59 connectors on coax show me some of the cables he made. The finished crimped connectors on the coax appeared to be secure when pulling by hand. I then suggested to crimp an outer ferrule to a RG-59 BNC connector with no coax / pin. After crimping we found that the outer ferrule came right off the BNC connector very easily.

Has anyone test crimped a ferrule directly on a BNC connector with no RG-58 cable / center pin and does the ferrule appear to be crimped securely when test pulling by hand? I am assuming that even with no coax it is supposed to be a secure crimp that should not easily pull off, correct? Has anyone needed to adjust the tension setting (if available) on their tool for the outer ferrule to crimp correctly on RG-58 BNCs?

reference picture of what I mean by outer ferrule (crimp sleeve) : http://www.l-com.com/images/Coax_with_callouts.gif

xavier60:
I had that problem with cheap RG58 crimp BNC connectors I got on ebay. The  ferrule walls were too thin.
I got firm crimps with replacement  ferrules with correct wall thickness from another seller. 
https://www.ebay.com.au/itm/Crimp-Sleeve-Ferrule-Pleated-Tube-Pipe-For-RG58-400-RG142-LMR195-Connector/152692980958?hash=item238d35fcde:m:m1lUxkQNOvO4gNYs8VbhBOg:rk:1:pf:0
rstor22:

--- Quote from: xavier60 on February 15, 2019, 10:00:03 pm ---I had that problem with cheap RG58 crimp BNC connectors I got on ebay. The  ferrule walls were too thin.
I got firm crimps with replacement  ferrules with correct wall thickness from another seller. 
https://www.ebay.com.au/itm/Crimp-Sleeve-Ferrule-Pleated-Tube-Pipe-For-RG58-400-RG142-LMR195-Connector/152692980958?hash=item238d35fcde:m:m1lUxkQNOvO4gNYs8VbhBOg:rk:1:pf:0

--- End quote ---

I had made some rough measurements/calculations of the BNC ferrules / outer ferrules that I tested. At first I thought it was the result of the difference between the outer ferrule ID and the BNC ferrule OD which was the issue (i.e. the smaller the gap the better the crimp?). This didn't seem to be the sole reason as the one that crimped the best had a 1.07mm difference where two others that did not crimp well had a smaller difference. I think it may be a combination of the above difference along with the OD of the outer ferrule as the one that crimped the best had largest OD (6.54mm) of the outer ferrule when compared to the others (6.31, 6.33, and 6.47mm). I think the thickness of the outer ferrule as you mentioned also plays a part in this.

Can you advise of the OD of the replacement ferrules that you purchased? (the link only specifies the ID).

Thank you.
xavier60:
Yes,
Original, OD 6.0 mm, thickness 0.2 mm
Replacement, OD  6.5 mm, thickness 0.5 mm
vk6zgo:

--- Quote from: rstor22 on February 15, 2019, 08:50:43 pm ---I found that the BNC center pin once inserted into a BNC connector clicks and locks in place and does not come out (for some RG-58 connectors). After crimping the center pin and the outer ferrule (crimp sleeve) and pulling to test the crimp everything seemed fine. On some of the crimps I have made I found that the outer ferrule did not crimp securely and pulling to test the BNC connection gave a false sense of security as it appears that the crimped center pin prevented the BNC connector from detaching from the cable (since the center pin is also crimped to the core of the cable).

I decided to do some more tests and crimped some outer ferrules (using an Xcelite ratcheting crimper) on the BNC connector (with no RG-58 cable / pin) and found that for some BNC connectors the outer ferrule just slides off after pulling slightly. I tried some unknown brands along with named brand Amphenol BNC with disappointing results. I found that I needed to adjust the tension dial to a higher tension on my crimp tool for the unknown brand BNC connector outer ferrule to crimp satisfactory to the BNC connector (though it needed A LOT of force for the ratcheting mechanism to disengage at that setting). Some other brands such as Provo BNC connectors had their outer ferrule crimped successfully at the lowest tension setting and seemed to be sturdy when pull testing by hand.

Today I had a colleague of mine who crimps RG-59 connectors on coax show me some of the cables he made. The finished crimped connectors on the coax appeared to be secure when pulling by hand. I then suggested to crimp an outer ferrule to a RG-59 BNC connector with no coax / pin. After crimping we found that the outer ferrule came right off the BNC connector very easily.

Has anyone test crimped a ferrule directly on a BNC connector with no RG-58 cable / center pin and does the ferrule appear to be crimped securely when test pulling by hand? I am assuming that even with no coax it is supposed to be a secure crimp that should not easily pull off, correct? Has anyone needed to adjust the tension setting (if available) on their tool for the outer ferrule to crimp correctly on RG-58 BNCs?

reference picture of what I mean by outer ferrule (crimp sleeve) : http://www.l-com.com/images/Coax_with_callouts.gif

--- End quote ---

The thickness of the braid is important in determining how tight the ferrule will be.
I have never tried just crimping the ferrule without the braid, but I would expect it to not be as secure as using it in the correct manner.
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