CNC Couplers (DIY - Cheap and Easy) Couplers

I am always tinkering around and trying to design cheap alternatives to store bought or specialty parts.  While CNC couplers are not all that expensive (if ordered from China...) I wanted to build a cheaper one.  

By using off the shelf hardware store stuff a simple coupler could be built that I think works a little better than the gas line and hose clamp option.

The cost to make these couplers is only a few bucks if you have an old tap and die kit around.  Even if you need to buy the tap kit it's still pretty inexpensive.  (And having a tap kit around is always useful.

Thanks for watching.