Does anyone know the purpose of this tool? The holes are threaded.
Fixture for flaring tubing , one of pieces needed
One of two pieces needed, the other being the actual flaring tool. Gooogle "flaring tool" for examples.
Are you sure they're threaded? They're often ridged - look like threads at first glance, but not spiral - to improve the grip on the tubing.
like the others have said part of a flaring tool, the part you are missing is on the top left