Driving relay using NO, COM and or NC

I have a SainSmart 5 Axis Breakout Board for Stepper Motor Driver CNC Mill board.  I want to drive a hot wire relay with it.  It has NO, COM, NC connectors - how do I wire these to the relay, and how is Linuxcnc configured for this? I connected the inputs to ground and NO, but an M3 does not trigger the relay

=0.8em  It has NO, COM, NC connectors

Those would be the contactors for the signal you want to switch with the relay: NormalyOpen, COMmmonm NormalyClosed.
To switch the relay you need to apply a voltage to coil (usually A1 and A2)

 

NO,COM,NC are (usually) the switched side of the relay.
Where are the coil connections connected to ?

Could you do a quick sketch of how you've wired the relay, you're description isn't quite clear.

If you want to drive a relay via another relay, connect one of the coil terminals on the relay you want to dirve to the + power rail, the the other terminal to the NC or NO depending on whether activating the first relay turns the second relay on or off and connect the COM to the ground of the power supply that the coil of the second relay is connected to.

I have this relay

www.amazon.com/gp/product/B01B60LPVK/ref..._title?ie=UTF8&psc=1

And this board

www.amazon.com/gp/product/B0093Y897A/ref..._title?ie=UTF8&psc=1

I've used X, Y, Z and A for the hot wire motors (XYUV), so besides the 5v and B output pins and the input pins, everything is used besides the NO/COM/NC connectors

I found when I send an M3 and M5 that I can hear the onboard relay clicking on and off. So the config is correct (NO is pin 14) - I just dont know how to connect the onboard relay to the external relay

External Relay Yellow wire to +5v
External Relay Blue wire to on board relay NO if onboard relay turns external relay on
OR
External Relay Blue wire to on board relay NC if onboard relay turns external relay off
On board relay common to ground of the above +5v supply

Imagine the on board relay is a switch. Pretty much what I said in my first post, but now with colours

I think my board is faulty - getting nothing (AC or DC) from ground to the 5V connector. I've tested using ground/COM etc - all combinations. The relay light on the board switches on and off though. Going to order a new board - I want a spare anyway (I'm cutting several thousand pieces of foam)

The relay contacts will have no voltage on them, that's why the one lead on the external relay needs to be connected to +5v and the common of the on board relay connects to ground. If you look at the diagram of the relay posted you will see what I mean.
The Bob board supplies no voltage to any on the NC NO COM or common contacts on the on board relay. Your board is not faulty. Get a multimeter use the resistance setting or continuity setting and place it across the NO & COM conatcs of the on board relay, the relay is just a couple of switch contacts activated by an electromagnet, as with a switch there is no power on the contacts until you supply that power. The power doesn't maigically appear on the contacts, it has to come from somewhere.
If you follow my description it will work.

Thanks - the continuity between NO and COM is working. I need some sleep now - so I can think straight again. Your help is much appreciated though

 

Simple diagram