Custom version of Fusion 360 post processor to enable "pierce only in the center" for holes

I have made this post processor if you are interested in having Fusion just pierce the center of (some) holes so that they can be driller/reamed manually.

This version is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE

It installs like the regular one from Langmuir but it’s marked 1.7 just to differentiate it.

In order to use it, create a cut operation and name it “pierce-only”. You can have other operations (with different names) for regular cuts. Typically you want to pierce holes first and then cut other shapes, but there is nothing in this modified post processor to require or enforce that.

It is important that the “pierce-only” cut operation does not use any lead-in, lead-out and that Pierce Clearance is set to 0 and consists of circular holes only. The post processor tries to detect failure to do so but it cannot be not fool proof.

When ready to post-process, make sure to enable this designated function.

The resulting G-code will only pierce in the center of the hole (make sure your pierce delay is adequate, but so any other parameter of the cutter):

I am still not sure in what language this post-processor is written in.

The code is now still under review in a branch on my github; if you know how to do, please have a look. In the future I might make a “release”.


Hi @manoweb

Thank you for this! I’m working with a friend who has a Langmuir to help him learn Fusion 360. I tested out the PP today on my Mac, and had no trouble posting G-code. But when we were trying the same on his PC, we kept getting an error. Paraphrased, it was “no linear cuts allowed, turn off lead-in, lead-out and set pierce clearance to 0. Post failed.” Digging deeper, it directed us to line 478 of the PP.

The resulting .nc.failed file looked exactly the same as my successful one, except that it had a line at the end declaring it failed. Otherwise, I couldn’t spot a single difference (except his was inches G20 and mine mm G21).

G90 G94

(Piercing center of hole only)
G0 X-39.964 Y21.9
G4 P0.5
G0 Z25.4


But we’d followed your instructions to a T: toolpath named “pierce-only”, lead-in & out off, pierce clearance 0. I even fiddled with the passes tab, switching between left and center offset compensation. And the selected geometry was a series of circular holes, specifically the top edges selected. (The above G-code is truncated to just one such hole). In NC Program we checked “Center pierce only detect,” turned off THC & IHS, had no spaces in the file name…

Any ideas? We changed the extension on the failed file to just .nc and he’s going to run a test with it, but it’d be great if we could get it working as intended.



Interesting. Would you be so kind to attach the .f3d of your Fusion design for me to try?

In practice, that error message means Fusion is trying to perform a linear cut on the layer that is supposed to be center pierces only.