Thoughts on Feeds and Speeds?


I was wondering if someone could provide me with some insight regarding Feeds and Speeds?

I’ve now been working with 3-Axis Routers since 2015 but to be honest all I’ve been doing was letting my gut ( and ears ) tell me if my Feeds and Speeds were right. Also, I’ve basically only ever used the 16’000rpm setting on my DeWalt 611 but recently I went full retard and, among others, upgraded my machine with a 0.8kw Spindle opening up some opportunities to go lower than 16’000rpm ( AFAIK down to 8’000rpm ).

So far I’ve been working on all kinds of materials like MDF ( mostly ), Hardwood, POM and Acrylic and especially with the latter I’ve been reading to go as low as possible to prevent the dreaded melting ( apparently less of an issue cast Acrylic? ).

Two days ago though I had somewhat like a revelation while watching an Onsrud Video discussing F&S with End Mills.
In the end - At least that’s how I interpreted it - It came down to the Endmills suggested Material specific Chip Load being the No.1 Factor followed by either your machines maximum Feed OR the Routers/Spindle RPM Range.

The End Mill manufacturer would ideally provide a material specific chip load chart ( calculated at DoC 1:1 Tool Diameter ) and you’d calculate how fast your Steppers can reliably move the machine as fast as possible giving you a theoretical ideal RPM starting point of the Router/Spindle. If the latter cannot reach the desired value the prior needs adjustments accordingly. If the latter can, more fine adjustments can be made by increasing the F&S until the surface finish deteriorates followed by backing down the value by 10%.

Now… Assuming this interpretation is right to begin with - Where does the RPM as low as possible or DeWalt 611 is too fast mentality come from when it comes to cutting materials like Acrylic? Am I missing something?

Thanks in Advance! =)

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I have limited first-hand experience but I thought this video gave a great explanation with some great information. Hopefully it’s of some use.

It’s a matter of balancing speed against feed rate so as to maintain a decent chipload — it’s all-too-easy at trim router speeds to spin so fast that rather than taking a chip the endmill is rubbing.

I got started on working through all this at: Tutorial on feeds and speeds

and am hoping to get back to it once I finish up my current project.

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