Phantom Barrel Thread Type?

[JonM]

I've got an idea bouncing around in my head for one of my Phantom barrels. If I were to model threads for a breech, what would they be?

[Lt. head-shot]

I know they are ACME threads, and a quick search of ZDSPB came up with this.

"Phantom barrel threading: 7/8"-14 ACME"

[JonM]

Thank you!

Follow-up question. How close are 7/8"-14 ACME threads to 7/8"-14 ANSI threads? I ask because Fusion 360 can model the ANSI threads automatically whereas the ACME threads would need to be modeled manually.

[XEMON]

Pretty far off ... ACME threads have a square profile ...
you can always 3D print a test piece ... The magic of 3D printer ...

Do you have access to something else than fusion? I believe SW has ACME threads in the library.

[Lt. head-shot]

Unfortunately, like Xemon said, VERY different.

[flyweightnate]

ACME Stub, specifically. They're shallower than a standard ACME. The flanks are either 14 or 14.5 degrees from the axis, vs 30 for a normal thread. Not quite square, not quite triangle, but a trapezoid.

Most machinists won't touch it, but with CNC it's just a special insert.

[JonM]

Thanks guys. I'm tossing around the idea of 3D printing a threaded breech for a Splatmaster so I could use a short Freak bored barrel. The only one I have that would fit and not stick out too far is my 8" Phantom barrel. Since I'm printing it, I expect tolerances may be a bit tricky, but it's just an idea I'm tinkering with at this point.