Spindle speed question

Another forward looking question as I gain some confidence with a month old x-carve. Is there any situation where I should go faster than setting #1 on the Dewalt 611 in terms of material, bit size, or level of detail?
I’m guessing I would only want to bump the speed for maybe metal or if I want to experiment with considerably faster feed rates with beefy bits.

I have the 750 with homing switches and z-probe using Easel. I don’t foresee going beyond MDF, birch ply, and hardwood but who knows.

Again, I searched for this in the forums but didn’t find anything definitive. Life is hard when you don’t know what you don’t know.


Consider a working envelope, wood have a wider range of settings that will work. Metals have a more narrow envelope.

There are two main areas of focus, in terms of what the bit desires in what kind of material.
First is SFM, or the speed of the actual tip of the cutter edge. A certain speed in a certain material provide the cleanest separation of the chip (the bite each flute of the cutter take each revolution)

Second is chip load. (referring to the bite above)
Chip thickness need to be within a certain range, again - a thickness that provide a clean separation. (example, go to slow on feed rate/too high RPM and slice is very thin and the bit will rub instead of cut. Rub = heat = destroyed bit)

So, SFM provide a RPM range which is diameter dependant.
Feed rate is RPM * Chip thickness

The rigidity of the system determine the depth per cut and ultimately give the max acceptable MRR (Material Removal Rates, Feed rate * width of cut * depth of cut)
A system that is not rigid will make the bit bounce and chip thickness will be all over the place. This will break bits.

So there is not a single definitive answer, it all depends :wink:

16K RPM is what you want to stay at as a rule of thumb.
If you have settings that work for 16K you can maintain chip thickness (and increasing MRR) by increasing RPM and feed rate by a similar factor. The upper limit will be where you have maximum MRR for that configuration.

What I’m taking away from this is I don’t have to ever worry about running the Dewalt too slow. Good.!