Understanding sounds {screaming}

Good evening second post for tonight,

I am trying to be a better CNCer by not stumbling onto a good cut, i am trying (failing mostly lol) truly understand the science of the cut, by interpenetrating the active cut as well as the entered F&S’s to better increase / decrease cutting , surface plunge speeds. for a more consistent cut.

To that end i have heard allot about feed a screaming bit, the article was very good in analogizing the bit to a baby a scream baby like a bit needs feeding because it / they are hungry.

Today whilst cutting the oak i took this vid (not headphone freindly) Oak Screaching of the screaming bit, to me i am already cutting quite fast but if i understand this sound it is telling me that it needs more feed? i looked at the cyclone collector and there was a nice steady stream of chips, also took suck it boot off and looked at the chips type load consistency and these looked good too, at the end of the run the bit it’s self was warm not hot able to put on cheek without any discomfort, so again call on the people who have spent more time listening to their machines more than me to :

A) Let me know am i on the right track about this being a scream or is this “Normal” cnc cutting sounds.
B)have i got it wrong and this scream is because i am going to fast and need to feed the bit by slowing down? - in that slowing down will increase the chip rate?
C) provide some notes / feedback on how to turn my baby SO3 from a screaming baby to a happy one

Thanks as always

I’m by no means the expert here, but if the cut turns out as expected, to the dimensions you wanted, and the machined edges don’t have any visible chatter marks or spots of tool deflection, then i’d say: let 'er buck.

Some toolpaths do tend to sound angrier than others, but that varies on the type of cutting you’re doing. Feeds and speeds are critical when cutting metal, you can get away with a lot when cutting wood.

If you’re planning on doing the same type of cut, in the same material, over and over, it might be worth your time to try to fine tune the feed rate, to maximize tool life.


What was your router speed setting?

Sorry I meant to add that to the post I was running at 20k

I will say that some bits and some materials just scream. Plywood + single flute straight bit + slotting = amazingly clean cuts, but it’s one of the cuts where I always wear my headphones. I’ve cut a fair amount of this combination and adjusted several things, which has made it a fair bit happier (like maybe the baby has cleaner diapers?), but it is still obnoxiously loud (and I’m half deaf in my midrange hearing). I was always taught (on manual machines) to adjust by sound, and you can definitely improve most cuts, but sometimes the baby will just not be happy while at the same time the cuts are splendid. Just my $0.02



I have had several old timers tell me to set my Dewalt 611 on the speed setting 3 and leave it alone. I have done woodworking for 35+ years and have used router tables and hand routing at maximum speeds for a lot of smaller bits. So when I was given the advise to set at 3 I thought that was too slow. But I have followed the advise and it seems to work. Routers do make a lot of noise and grain direction has a lot to do with that. When you cut plywood you may be cutting two different layers at the same time and the plywood structure is set up so grain direction is 90 degrees grain direction per layer. So one cut may scream and the next deeper cut on the same pocket may not make as much noise. As someone above said if it works then do not worry about it. If however you are getting burning or rough cuts then look at speed and grain direction. In the design process you could turn 90 degrees and try again and see if you get a better result. Trying to go deeper and understand the theory is important but do not drive yourself crazy with every detail. As time goes by you will learn more and understand more. Wood is a natural product is not always consistent even in the same piece of wood.

1 Like

This topic was automatically closed 30 days after the last reply. New replies are no longer allowed.