This one goes to 11!

[b_m_hart]

OK, so the title is from Spinal Tap - a great spoof on Rock music from "back in the day".  If you've seen it, you remember where the guy's talking about his amplifier, and how it goes to 11 (instead of "just" 10).

One of the things that I've come to learn, either by reading, or through the errors of my own ways, is that power tools of all flavors, Festool included, are NOT always best used at 11 (max power / speed / etc).  I don't question the validity of this, I just am curious as to why that is.  Why would a router bit turning faster do anything but make for a cleaner cut?  Why would you need to turn your TS55 or TS75 to a lower speed for certain types of materials?

Is there some sort of general guideline or principle that can be used as a way to know when to use what speed?  Or is it something that's learned by "oh crap, burn marks"?

 

[Steve Jones]

In the case of router bits (and drill bits) the ideal speed is not RPM but the speed that the cutting edge passes the material, for large bits a slower speed results in the same cutting speed (the ideal you're aiming for is a match between cutting speed and feed rate).

This also applies to turning material on a lathe, larger diameters have to revolve slower (lower RPMs) to achieve the same cutting speed for the same reason.

In the case of the saw blade most saws don't have variable speed, however the Festool ones do to allow for cutting different materials, in my case the only time I slow down the saw is for cutting plastics which tend to melt or soften and will "weld" themselves back together behind the blade if I don't.