CAMheads CNC Router Forum By: CAMaster CNC

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Clayton.Lott 07-01-2019 07:46 PM

Screaming bit
Need some help for the new guy. Cutting 1/2 5x5 birch with 1/4 in upcut and it screams unbearably. I've tried rpm ranges of 10000 to 16000 and Ipm ranges of 50 to 150 with no changes. Also tried a second brand new bit. Throw some knowledge out there for me guys. Thanks

Jim Becker 07-01-2019 08:36 PM

Honestly...nature of the beast. Cuts like that require hearing protection.

Clayton.Lott 07-01-2019 09:18 PM

So this is something I should expect on all my cuts or is there something I'm doing to cause it? Such as bit size, material, etc

Ken Rychlik 07-01-2019 09:48 PM

Try bumping your cut speed up to 250 or 300. In my experience a screaming bit is under worked. Need slower spindle speed or faster travel speed. Another thing to watch for is chips. If your making dust, your going to slow. You need to make chips.

Compression bits are the worst for screaming. I still use a lot of straight bits just for this reason.

bmilam 07-01-2019 11:58 PM


Originally Posted by Clayton.Lott (Post 81514)
So this is something I should expect on all my cuts or is there something I'm doing to cause it? Such as bit size, material, etc

Not necessarily. I really haven't pushed my machine and cut thru in one pass so mine makes little noise compared to dust collector. Other bits I'm sometimes wondering if the bit broke because they are so quiet. Every once in a while I get one that screams like you are talking about.

Xray 07-02-2019 01:17 AM

A screaming bit usually indicates a dull bit, and/or one with improper RPM's/feedrate for the job at hand. Could be that you are taking too much of a bite as well, try reducing cut depth if practical.

The real JP 07-02-2019 04:45 AM

Download a chipload calculator to help you get a starting point with speeds and feeds.

You want chips, not dust. try 13,000-300 you can bump the feed or rpm up or down with the keyboard.

I have the "us tools" app on my iphone. ( red square with chrome US )
It gets me close enough to get cutting.

Think of it like when you use a skillsaw. Go too slow and it burns and shrieks. Go too fast and it gives a splintery cut. Same deal with the router, you'll get used to the sound of it when it is cutting good. Any change will draw your attention.

guitarwes 07-02-2019 09:58 AM

50-150 ipm is WAY too slow for those rpms (10k-16k). Try 12000rpm at 240-300ipm full depth pass. A screaming bit wants to be fed (use slower rpms or faster feed rate).

Clayton.Lott 07-02-2019 12:17 PM

Thanks. I will try out some of this. Does everyone use two flute bits? Ever try three flutes? Straight bits?

tmouse 07-02-2019 01:13 PM

Three flute would need even more speed and slower RPM

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