Some basics: a) very pure solid IGL copper conductor (lead) of Monorail is softer than brass b) Copper is too soft for a plug so we build from brass which will not bend when used or “deform” c) If the brass tip of the SIS plug is carefully machined to have “threads” with a precisely sized opening, it can cut and re-shape a softer IGL copper conductor that enters it.
So, the soft copper of Monorail conductor/lead is revealed in preparation for assembly. When you push the prepared cable into the SIS plug, the soft copper lead will find the hole. Then when you turn it 1 or 2 times, the harder brass, SIS core will catch and cut into the soft copper core.
When you feel this, put the cap in place and screw the SIS plug into the cap. This action: 1) turns the soft copper deeper into the SIS core 2) “Mashes” or “forces” the ground up against the SIS body to make “negative” contact from pressure 3) seals the red jacket at the exit tight so the cable will not come loose from plug and the cap will not come loose from SIS body. Also air/oxygen will not enter sis to contaminate ground contact
The tip/core connection with the Monorail center lead is air-tight and very strong, forever. Better than a solder connection!
If you unscrew the SIS plug and then unscrew the Monorail cable you can see the soft copper has been shaped to meet with the SIS core in perfect harmony. Photo below shows what happens inside the plug where the IGL conductor of the Monorail enters the tip portion of the SIS plug.