Spindle Noise - Episode 143

Is a spindle quieter than a router?

Before taking the router off the machine it is a good opertunity to compare the noise against the new spindle. Doing it later would require reassembling the SuperPID so now is the best time to do it. The process is not scientific but only serves as a comparison between the two. 
The audio in this video used in the spindle / router comparison are recorded on the same microphone and it was not moved between tests. The levels are as recorded so offer a realisic comparison.
The test was conducted at 10,000rpm which was chosen because it is the speed I use to cut a lot of my projects. The SuperPID allows my router to run at slower speed but maintain the power. A spindle works the same way allowing it keep constant speed under load.

The Results
 The router, as expected, was louder than the spindle but not by as much as I thought it would be. The 9db(A) difference represents an 8 fold increase in the power of the noise. The Decibel scale is logrithmic and a change of 3db(A) represents a doubling power. 3db(A) is also the smallest level increase that the human ear can distinguish. Exposure to noise levels of 85db(A) or higher can cause permanent hearing damage.

These tests are of only limited use as it is not normal to use a CNC machine and not cut anything. Once you start to machine your project the addition of dust collection and the sound of the router bit cutting through the material will easily increase the noise level above 85db(A) making the wearing of hearing protection manditory. Unfortunately I do not have level measurement of the old router while cutting to compare it against the spindle.
There will be an advantage when doing fine work as the cutter will not make a lot of noise. eg when I do a final pass on a 3d project I don't usually put my dust connection on and because of the minimal amount of material being removed the cutter makes very little noise.

I am looking forward to getting the machine up and cutting just to see how noisy it is.