Are these Chinese spindles really up to the job?

Last weekend I was pottering about, a bit of this and that. I needed to rout out a small channel for a chopping board, so picked up my generic 1000W router, 1/4" bit and got to it. As I was cutting through, probably a 9-10mm DOC and a rate of 10mm/s (wild guess), I started to think about how easily this router cuts through material, whereas the spindle on my MPCNC has to be gently coaxed through material to avoid significant deflection. So:

  • I wonder if I should routinely use deeper cuts at lower speeds to reduce the ‘moment’ applied to the end of the tool (this may be nonsense, perhaps it makes no difference to the degree of deflection when you consider the sum of all the moments applied in a deeper cut).
  • Is the power of the cutting tool (500W or 1000W) well correlated with angular momentum? Presumably, degree of deflection is in part related to angular momentum, as well as rigidity of the CNC itself
  • Am I really talking about torque?
  • Why didn’t I do a degree in a proper subject like mechanical engineering?

I’m going to buy a suitable router, mount it, and directly compare the two, unless this has already been done (please, someone save me from this…I’m poor)

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There’s another factor that you may not be considering here. When you’re routing something by hand, you have feedback that you use to compensate for deflection and whatnot. The CNC machine knows nothing of any of that. It just moves the tool from point A to point B at the speed you tell it to. It has no concept of using more or less power to hold lateral positioning, or to push through a knot. And let’s be honest, odds are, you could probably win a shoving match with your CNC. :muscle:

Yes, you’re right that I’m hugely oversimplifying, but I feel like I could use the router with just my fingertips and still cut more effectively than my spindle can. However, ‘feel’ isn’t a great metric for comparing two bits of kit :smiley:

I kind of had the opposite experience. I was making template to cut LR side plate using a follower bit. I had to muscle it so hard I was worried if I slipped in any way I would hurt myself. I had to brace the table I was working on up against the wall. That is when I realized how hard we push these things.

Yes, 1-3 tool diameters max

Um, not in the way I think you mean, the end of the tool is still getting the same force plus all the rest of it is also getting force applied now…deeper cuts will always apply more force. Speed is a matter of machine rigidity. (loosen your grip when you use the router by hand and you will realize that thing can be a bucking bronco and jump right off the table) But when the cutting parameters are within reason you already know there is very little force, and why something like the LowRider can just sit on the table and not move.

Lost me here. Think of it this way, you just need enough. More does not help it hinders. Strap a lawnmower engine on the MPCNC and would it perform better than a 500W router…nope worse because of the weight. My point is it is a balance. Machine rigidity, and cut parameters are far the most important, router power has very little to do with it as we are pushing the frame harder than anything else.

I learned more here than in school, my degree just makes people believe what I say.

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I think the momentum of the tool decreases the deflection.

A dremel for example builds up speed and the momentum of the spinning cutter is what grinds away at the workpiece, as opposed to a traditional low-rpm mill that bites off huge chips by just pushing the cutter through the material with extreme force.

A 20k rpm router is somewhere in between, where it should be cutting, not grinding, but the chips are fairly small and the momentum of the tool is doing some of the work. If you go for a higher power spindle, it might have the same but perhaps lower rpm, meaning greater torque and less momentum. Moving toward the traditional mill with fat chips, the load on the frame (and therefore deflection) is going to increase.

Thats how I think of it broadly, but of course there are feedrates and depth and cooling issues that also come into play.

I do know the dewalt cuts better than the chinese spindle I have, less tool stick out from the mount.

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