Friday Livestream #8 - Making Sense of Speeds and Feeds

On Friday we’ll be doing a short session about how to decipher speeds and feeds charts so that you can approach foreign or unknown materials with greater confidence. Let me know what you’d like to know about the topic, or if there was something regarding speeds and feeds it took you awhile to wrap your head around!

Livestream will be at:


RPMs. In which cases and why you choose to pick a low, medium, or maxed out value, and do you ever start from SFM. There have been multiple discussions here, I’m just curious to hear your position on the matter.

(I would have added “do you believe in chipload?”, but you said “a short session”… :slight_smile: )


Chipload is life lol. It’s half the equation when I’m calculating feedrate.


@Julien Good point about RPM and SFM. With a spindle I approach with an SFM that I want for my particular path, it would probably be different if it were a router, so a discussion that caters to both camp would be welcome.
Please get into Chipload I feel like it’s important to understand regardless if it’s a simple 2D path or a complex 3D adaptive. Also how do you calculate it for a ramp, or a Helix, it there a good rule of thumb?

One other thing, where do you bring MRR into the equation? If there’s no problems I usually ignore it, I’m not a production shop, but I cant shake the feeling I’m missing something important there.

  1. Chipload/F&S reccomendations or tips for really small endmills.
  2. Any advice or tips for using extra long cutters (deflection and it’s effects on chipload, compensating for sometimes unavoidable chip recutting)
  3. Ditto on what’s been said about SFM and MRR
  4. Choosing high axial+low radial DOC vs. low axial+high radial DOC (any tips or warnings on how our machines handle the forces, which you recommend using for certain types of cuts or which you recommend using in general for the nomad/shapeoko/hoobyist machines)
  5. Tips/tricks for inevitable chipload spikes during certain cutting/pocketing maneuvers when using CC programmed tool paths due to no lead-in, ramp-in, adaptive clearing.

I would say try to “dumb it down” as much as possible for us monkeys, but you already do an awesome job of explaining technical things to us laymen! Looking forward to the session!


What do you do if the manufacturer hasn’t specified any tool guidelines or specifications for the tool you’re using?

(Looking at you Carbide 3D)

Even calculators like G-Wizard like to have the manufacturer’s specs as a starting point.

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for CC paths either you need to pick less aggressive F&S, or feed your gcode through
to normalize the forces for a 50% cutter engagement

(the CC folks have implied on the forum that they want to have this kind of behavior in CC but it needed a bunch of UI work first so delayed to the future)


I had your recent programming awesomeness in mind while writing that part :laughing:
And I should have worded it as more a question of his personal preference as opposed to typical “procedure” which may be as simple as you said.

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How to choose an End mill type (flutes, geometry) and how that effects feeds and speeds.


Feeds and Speeds vs Noise (real sound levels with a meter, open machine vs enclosure, etc). While some have no neighbors, so have very close neighbors…and noise matters.


Don’t look at us, look in Carbide Create! We gave you some starting points for our tools and common materials already. :man_shrugging:

And for tool vendors that don’t have data, just go to a different vendor and look up something comparable. A general purpose 1/8" endmill from harvey is going to work just like one from Lakeshore, is going to work just like one from us. Don’t overcomplicate it, small differences aren’t going to matter on a desktop machine in softer, non-ferrous materials.


Ahh, that’s where they’re hidden… I was used to Fusion 360 from before I bought my Nomad so I’ve never used Carbide Create. I was looking for information in the support pages and shop but there was nothing there, so I usually ended up using values from your MaterialMonday videos.

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Adding onto feeds and speeds vs. noise, what it sounds like when feeds and speeds are “right” vs. when they’re “wrong” in various ways (e.g. chatter, load spikes, just cutting too hard). As a newcomer to milling, basically all the sounds are scary, it’d be great to know which ones are worth worrying about and which aren’t, as well as what I can do about which sounds.

On a similar note, how to evaluate the results of different feeds and speeds, e.g. what should I look for on my workpiece after a roughing pass or a finishing pass? What’s the best I can expect to get out of the machine if I do everything right?

Also, +1 for axial vs. radial DOC. I found it really weird that all this work goes into making a tool with say 0.5" of perfectly sharp flutes and all the official resources say to use nothing but the first 0.01" of the tool, I’d love to learn more about how to improve on that.


1:30 PST is the start time as previous livestreams, correct?

Correct. And if you miss it, all episodes will be available here after broadcast:


But we can’t ask you silly questions face-to-face after the broadcast… I mean good question yes that’s what I meant good questions…(grin)


Hello, if possible, any suggestion on feed and speed (and DOC) for a facing operation on the supp. wasteboard. After cutting my board (my first cut ever on a cnc) that’s where i am now…
I intend to use a small Amana 45525 (similar to the Whiteside). Any advice would be appreciated.

You’re just skimming a mm or so? Go as fast as you want. The datasheet for that bit is all for a speed of 18k rpm.

Can we get a good Chunk of Fusion 360 on this one? It’s more flexible with speeds feeds and tool paths, so it would be helpful to direct some attention there.

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Yes one mm in two 0.5mm passes @ 18K rpm. So i’ll go at 90-100 in/min. Thanks Neil. Also, when i zero in the tool, my understanding would be to use the center of the cutter (1-1/8 Dia).