Properly connecting a BNC connector to coaxial cable is an acquired skill. You need two tools — a wire stripper that can cut through the various layers of the coaxial cable at just the right location and a crimping tool that crimps the connector tightly to the cable after you get the connector into position. BNC connectors have three separate pieces, as shown in the following illustration.
Here’s the procedure to attach the connectors yourself:
Slide the hollow tube portion of the connector (lovingly called the ferrule) over the cable.
Let it slide back a few feet to get it out of the way.
Cut the end of the cable off cleanly.
Use the stripping tool to strip the cable.
Strip the outer jacket back 1/2 inch from the end of the cable; strip the braided shield back 1/4 inch from the end; and then strip the inner insulation back 3/16 inch from the end.
Insert the solid center conductor into the center pin.
Slide the center pin down until it covers the inner insulation.
Use the crimping tool to crimp the center pin.
Slide the connector body over the center pin and inner insulation but under the braided shield.
After you push the body back far enough, the center pin clicks into place.
Now slide the ferrule forward until it touches the connector body.
Crimp it with the crimping tool.
Don’t get sucked into the trap of trying to use easy “screw-on” connectors. They aren’t very reliable.