So I had a really tough carve on my AltMill 2x4 this weekend that totally went south probably due to bad feeds/speeds management on my part.
So here’s my question to the Community: What is your approach for carving super hard woods like hard maple and walnut when it comes to feeds/speeds and depth per pass?
I think I got greedy and set my depth per pass too high. I was using a 1/4 inch (6.35 mm) “Hog” bit from IDC Woodcraft for the rough carve, and was taking 2 mm per pass at about 2600 mmpm.
My stepover was only 50%, but like any carve there are moments where my CAM software had it doing its initial plunge with the full bit engaged and then making really long runs.
The wood was absolutely screaming and the chatter was ruinous in the end.
So in general when carving really hard wood, is it better to make shallow depth passes of like a millimeter or less, and if so can I still move the machine pretty briskly?
In other words, is it conventional wisdom that you opt for low depth/high speed for really dense materials?
Or should I just slow the hell down?
The carve was already over 2 hours with my settings (because I’m basically eating down through a 40 mm blank to end up with a neck that’s 20 mm at its thickest but has an angled headstock).
I think it would help to know the details of the cuts you were attempting.
What CAD/CAM software are you using?
What species of wood?
What were you feeds, speeds and depth of cuts?
Climb or conventional?
Type of toolpath - profile, pocket, etc.?
But first, a couple of observations - I have a ¼” Hog. I also have a ¼” Beast. AltMill 4 x 4. Cutting the same exact toolpath the hog screams and the beast cuts like butter. As far as I can tell, the only difference is the length of the cutting edge (hog being longer). I routinely cut maple, walnut, cherry and sometimes purpleheart (much less forgiving than the others). With the beast, I set it to 125 to 200 inches per minute (3175 - 5080 mmpm) at 11,000 to 14,000 rpm, ¼” depth of cut is the norm. You mentioned the hog screaming - screaming or screeching is usually caused by having the rpm too high for the feedrate.
And yes, shallower cuts at the correct feed and speed are better than deeper cuts and slowing the feed down. It all comes down to chipload.
Hard maple with a couple of strips of purple heart (10 mm thick). The blank was 915 mm x 115 mm x 40 mm
Feed at 2600 mmpm, plunge at 1600, and (probably where I went wrong), 2 mm depth.
Climb
The 3D Roughing toolpath in MeshCAM, with an estimated time to complete at about 2.5 hrs.
Thanks for the tip on the Hog vs. the Beast. I just broke my second Hog on the carve I mentioned (again, probably my fault). I’ll definitely check out the 1/4-inch Beast. I have the long 3/8-inch Slayer (Deep Slayer), which works great, but not always the best diameter for the workpiece I’m trying to carve.
From what you’re saying, it sounds like I was probably also running the spindle too high on my AltMill 2x4. I was running it at 18000. But I was only running at 2 mm depth per pass.
