This is for the pictured brass heat-set presses that are available on Amazon. It neatly holds (10) M4 internal threaded brass insert mandrels.  After doing a short run of parts with multiple thread inserts, I got tired of misplacing, dropping and losing my heat-set insert mandrel.  This will neatly hold up to 10 heat-set inert mandrels.  You will need (10) M4 brass heat-set thread inserts and (10) M4 X 10mm set screws for the mandrel holder.  As well as (2) M5 X 14 socket head cap screws to attach it to the top of the press.

Add a drop of thread locker compound to the set screws so they don't turn when installing or removing your mandrels.