The mother of all CNC programs

I’ve been working on cocker threaded Phantom bodies for quite some time, and the latest incarnation is a ‘full round’ version.  I had a job shop do the internal machine work on them as I didn’t yet have the big lathe running (which I’m now having some regrets on – the cost was substantial, it took over 5 months, and despite what I was told at first, they want the invoice paid in full NOW).  I wanted to do the final machining in a single setup, as they’re round and alignment would be a concern were I to try multiple setups.  Furtheremore, a single setup would require 4th axis operation, as there are features on the top and bottom of the part.  In short, there were a lot of ‘firsts’ for me in this project, and it’s the most ambitious CNC program I’ve yet done (experienced CNC machinists would laugh at its simplicity, but hey, I’m learning).

Roundhead body on the mill
Detent slot milling operation in progress

I broke the program down into pieces, some of which I had already done.  There are 5 subroutines in use:

  • sear slot
  • threaded insert counterbore
  • feed port
  • threadmilling for insert counterbore
  • detent slotting

The sear slot is first, then the underside counterbore, rotate 180 degrees, then the topside counterbore and feed port.  Tool is changed to the threadmill, top counterbore is threaded, rotate 180 degrees and thread the bottom counterbore.  Finally switch to the ball end mill and run the detent slots.  Total run time is still over a half hour, which I hope to cut down a bit by removing some unneeded ‘air’ cuts, increasing feeds, etc.  Still, the satisfaction is immense – I’ve had a lot of tools (the 4th axis, tooling plate, tailstock, bullnose live center, etc.) sitting idle for a very long time (they were all purchased with this project in mind), and it’s a great feeling to finally have them put to use.

Mach3 while running the CNC program
The three tools used in the program, held in A2Z endmill holders
The three tools used in the program, held in A2Z endmill holders

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