Undercuts with slotting cutter?

Does anyone know if it’s possible in the Fusion360 → MeshCAM → Carbide Motion workflow to add a slotting cutter to create slight undercuts in workpieces?

I have a case where I need to make a coarse internal thread, similar to 3/4" NPT pipe. I designed so that I have about 0.95 revolutions of thread - just under one full turn. That means I can technically flip the workpiece and hit all surfaces with a “top down” view, if I approach from both sides. But the flip and re-registration are creating challenges, and even if I get them all worked out, they’re going to slow down the workflow considerably.

What I’d love to do is use a slotting cutter, or even a square endmill with significantly reduced shank, to hit these undercuts from the top only. My thread depth is only about 1.6 mm, so that’s the max overhang I will have.

I’m cutting in plastic, and plan to rough with a Type O to start. Stock thickness is about 15-20mm total, with the internal thread at about the 50% mark through the stock. Again, I have less than one full revolution of threads, so pitch and proximity of neighboring threads aren’t an issue.

Has anyone used a slotting cutter successfully on the Nomad3, and if so, are there special considerations when setting up the cutter in MeshCAM?



Could you just skip Meshcam and generate a threading toolpath in Fusion?

Yeah, probably want to use fusion for this tool path. Simulating the cutter and holder will also help you avoid easy-to-make mistakes.
Fusion CAM is a pain for a beginner (if you’re as much of a beginner as I am) but it’s quite a bit more flexible than meshcam.
I’ve been buying Harvey tools and they have libraries you can import into fusion for their cutters. Maybe other manufacturers do too? That’s especially helpful for odd cutters. I haven’t tried my undercutter yet but I do have one :grimacing:

1 Like

Sounds like I need to bite the bullet and learn CAM within Fusion360. MeshCAM feels like an intermediate wedge in the workflow anyway. Any time I need to make a small change, I have to toss that file completely, go back to F360, and go through the exports and conversions all over again.

Any rules of thumb on picking a slotting cutter? I need at least 2 mm of cut, so was thinking of a 1/8" shaft with 5/16" cutter. Or I could do a 1/4" shaft with 7/16" cutter. That seems like a more rugged tool, but cutting on the sidewall, it will require more torque for the larger diameter.

Bite the bullet. Once you get going with F360 CAM you are not going back.

1 Like

For your torque concern I bought HSMAdvisor. The nomad is pretty lightly powered and I’m so noob that I just have no idea what reasonable starting points are. It helps me find sane chip loads with low spindle power requirements while maximizing tool axial engagement which improves tool life (versus shallow axial + large stepover).
When you set up a tool library (I just copy paste from Harvey’s library into my own fusion cloud sync lib) in fusion you can just export your tools and import into hsmadvisor to help you set up different cutting profiles (materials, roughing versus finishing etc) with the exact tools you have.

Good luck! There’s kind of a lot here and I’m still just scratching the surface but it’s a good time to be a hobby cnc user :slight_smile:

Mind if I ask which one you picked as your first to try?

Sure. I have a very specific project in mind that only needs a 0.5mm lip so I got the tool with the smallest overhang that could do the job Harvey Tool

1 Like

This topic was automatically closed 30 days after the last reply. New replies are no longer allowed.