View Full Version : PC versus Rotary RPM's

Nov 3rd, 2005, 05:42 AM
Can someone clarify the actual speed in revolutions for me.
I told a customer speed are in revolutions/rotations per minute for the rotary (ie 1200rpms) but did not know what the actual speed used in porter cables as I only see speeds 1 to 6 ? what is that running at ?

thanks for clarifying

Nov 3rd, 2005, 05:57 AM
The main reason it is in speeds 1-6 is because it is about impossible to say what "rpm' the PC (I assume you mean G-100 model?) is running at. You could do oscillations per minute maybe, though that doesnt take into acount the head spinning. The motors rpm doesnt mean anything, becasue the head spinning, and the head oscilating/orbiting cant be added together. So it is kind of hard to say.

Mike Phillips
Nov 3rd, 2005, 06:03 AM
Because when you push hard on the dual action polisher both the rotating action and the oscillating action can stop, it becomes a mute point what the speed of either of the two actions are, the hope and the goal is that in the long run, the tool/action gets the job done.

In our Saturday classes, in an effort to demonstrate why the dual action polisher is so safe for the average person to use I'll set the speed setting on 5.0 and then hold my hand against the face of the pad to start with and let the audience see the pad rotating and oscillating by placing a black mark on the yellow W-8006 foam polishing pad, and then I'll grab the pad firmly with my hand and completely stop any movement of the foam while the motor continues to run.

I then contrast that to the action of both a traditional orbital buffer and the rotary buffer by turning these machine on and showing how they operate and the point becomes pretty clear.

Nov 3rd, 2005, 06:06 AM
excellent, thanks guys, I'll employ the term "oscillation" for pc

the other pc
Nov 3rd, 2005, 06:49 AM
Porter Cable lists the (no-load) speed of the PC as 2500-6000OPM.

So in theory, "speed 1" is about 2500OPM and "speed 6" is about 6000OPM.

If the relationship between dial position and (no-load) speed were linear "speed 3" would be about 3900OPM and "speed 5" would be about 5300OPM. Unfortunately, speed control dials don't necessarily have linear response so it's hard to know for sure without actually measuring it. I'm sure somebody at Porter-Cable knows.

You can't directly compare a rotary RPMs to orbital OPMs anyway, since every point on an orbital's pad is traveling at "orbital velocity" (unless it's a DA like the PC, then it gets even more complicated) and the speed of any given point on a rotary's pad is proportional to drive speed and the distance from that point to the rotational axis.



(another chance to use that graphic again, I knew it would come in handy)