Without a file it is hard to make suggestions.

Have you tried just drilling one hole and doing a transform rotate operation for the remaining holes?

IMHO you will never hit that tolerance with hardened D2 over that large of an area. Deboer isn't listing any end mills for hardened steels that I can see.

What material is it? Like @Jobnt said this is a tall task for a part of that size!!!!!! What machine and what kind of holders are you using? What end mill brand are you using? Union Tool makes specific tools for machining hardened materials.

There is no simulation for lathe.

I created a video for you showing how to create a cavity from a solid model. https://www.dropbox.com/scl/fi/hk066mbfanw9r8e3fx53a/CreateMoldCavity.mp4?rlkey=bfu7st9uro7iveufb543cvsfw&dl=0

We have a Snagit license here at work, that is Techsmith.

Glad to help! I am constantly learning from others here!

@berntd See this video I made of your file. https://www.dropbox.com/scl/fi/whbfnzy2kd2u8ij7u81kp/2019Help.mp4?rlkey=wrmf647mopqjcysr1byt3vwwj&dl=0

I use Cimco.

This is an example of continuous improvement.....have time for everyone to input ideas/ suggestions.

Silence speaks volumes here.

You might find it easier to start with wire frame chaining. Create a Curve on the top edge of the hole you want to cut. Do this on a new level. Then turn off your solid. Solid chaining works well but you need to make sure the selection is correct as @AHarrison1 stated above.

Your file shows each toolpath with 1 solid chain selected, this looks correct. Work on using Levels to separate your geometry. Move your solid body to a new level and name that level "Solid Model". Then move all your surfaces to a new level and name it "Surfaces". Then if you need any wire frame geometry put that on another level and name it "Wire frame Geometry". This way you can turn on and off the other levels making your geometry chain selection easier.

Make sure you are in the “Right Gview plane” then select Transform rotate. Or use Dynamic transform.

Create a standard for levels such as doing them in intervals of 10. Possibly having fixtures on a dedicated level in all files if possible. Have a dedicated level for Notes on the part/ job and programming so anyone that opens the file can view these. Implement the use of View Sheets to easily pick views and or levels. If there isn’t anything currently in use create a logical file storage structure system for storing and accessing files. Try to have all files for each part or job contained in the same folder whenever possible. Have a revision naming policy so everyone follows the same process. Develop a verification process that everyone will follow when G-Code is created. Insist on having comments added in every tool path. I have HSM Advisor for speeds and feeds. We use a lot of Helical Solutions/ Harvey tools, their machining advisor is excellent.

You forgot to add GibbsCam to that list!!!

Without a valid Ziptogo file no one will touch this since it reeks of piracy IMHO.

The Machsim is more or less just bling unless you have a kinematic aware post processor from Postability or In-House Solutions. Then you have to license the Module Works module for the full Machsim. Having a tested Post Processor, a matching Machine Definition and Control Definition (these are not part of your Machsim file) are the first steps in Mastercam. The post processor translates the NCI file that Mastercam creates in the background into G-Code for the specific Machine/ Control. The Machsim that you can build and or comes with Mastercam is only verifying the NCI code not the actual G-Code that the machine will interpret. This is why there is a need for verification software such as Vericut or Camplete. I can show you files that verify fine in Mastercam and on a Machsim but in Vericut it shows the collision as it is verifying the actual G-Code.

Those Y keys don't look used, I assume it is not a Y-Axis machine. Rotate the turret until one of the round hole stations is the current tool. Then look into the hole for a drive shaft.

Look inside the machine, if it is a Y axis it will have live tooling. Also look at the tooling cupboard and see if they have live tool heads for it.

Without seeing the shape or file I would suggest Scallop or Equal Scallop or Flowline.

Without a post processor this is pointless IMHO. https://www.inhousesolutions.com/resource/zip2go/

A ziptogo is needed to get the Machine definition, control definition and post processor. The other option is checking with your reseller.

I don't have MC2020 installed. You will need to link a ziptogo of a current file with toolpaths using this machine if anyone will look at it.