How to mill internal threading?

Hello, I want to mill something like

The lid is not hard to model, but I am not quite sure what type of tool to use to create the threading. I’ll be modeling everything in Fusion 360.

Has anyone done anything like this?

I am no expert and just getting to know the cnc, but I think you could probably do it with a single profile thread mill.

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The thread mill is the best solution. That said, many of the G codes used for thread milling are not supported by GRBL. It is possible to rewrite the g code to handle the thread mill operations within GRBL.

See there:


The threading on that lid is very coarse (to fit the jar) and looks to be pretty forgiving. The suggested single profile threadmill may work, although they max out at a depth of cut which may not be deep enough for the threads on your jar, plus they cut a sharp V so would be many many passes to get any sort of round profile.

I think in a perfect world you would want some sort of cutter with a rounded profile, sort of like this:

Of course you need the diameter to be small enough so you can make a helical thread, rather than just a concave groove in one plane. Still would need to make multiple passes but may get you closer.

OR, you could 3D print it :wink: