Is the Dual-Action Polisher Safe?

[Kevin Brown]

Re: Is the Dual-Action Polisher Safe?

Junkman, good to see you hanging around MOL a little!

One thing to keep in mind when using 4" pads on a D/A - you will be concentrating the energy of the tool into that small area and the possibility of damaging the paint goes up significantly. If you get really aggressive with a 4" pad you run a much higher risk of burning the paint, or twisting it on a painted bumper cover. These smaller pads can potentially change the safety factor of the D/A and should be used with this knowledge in mind.

Believe it or not, I have found that to not be an issue with the focal pads and the PC, even with the more powerful PC-7424XP...

...These pads are marketed to be used on a drill for spot repairs but I don't advise anyone do that. As you know, a drill is going to reproduce the action of a true rotary and the opportunity for a catastrophe is 10-fold compared to the PC.

I think you are both trying to make the same point, perhaps.

Mike is likely saying:

If the random orbital's rotational speed steps UP to wickedly fast (like 10 turns per second, or 600 RPM), the damage potential is higher.

Since the pad is smaller, all forces placed upon the paint will generally be higher, too.
To avoid a mishap, occasionally check the temperature of the paint surface . If it is excessively higher than what you would realize using a larger pad, lighten up on the applied pressure, drop the machine speed, or both.

Junkman is likely saying:
Since the pad is mechanically rotated, there is quite a bit more torque on hand to push through things (paint included). So, unless some pretty severe pressure is placed upon the drill or something BIG gets in the way of the pad, there will be no extreme variance in relation to the supplied rotational speed.

Whereas 600-700 RPM is likely the highest rotational speed you might see with a random orbital, several cordless drills can exceed 2,000 RPM. Therefore, if you decide to use a drill as your machine of choice, drop the speed and occasionally check the paint surface for excess heat.

Both of you make useful points. Bottom line:
Either machine can be your best friend... OR your worst nightmare!

[Michael Stoops]

Re: Is the Dual-Action Polisher Safe?

Kevin Brown steps in once again to crystallize our thoughts!!

Yes, a smaller pad used on a D/A will indeed provide more cut than a larger pad, everything else being equal (foam construction, pad face contour or lack thereof, pressure, speed, liquid used). This is why 4" pads used on a D/A are so popular on the VW Vortex forum; those guys are generally dealing with pretty hard paint and the smaller pad concentrates the energy of the D/A into a smaller space, and they get more cut. The potential problem is that people have been lulled into thinking that the D/A is 100% totally and completely idiot proof. With that perception drilled into their heads, they lean on a small pad pretty hard, and dwell in one spot for too long, and the next thing they know - damaged paint. Yes, when used according to the guidelines Meguiar's teaches, and obviously using the methods Junkman shows in his videos, chances of damaging paint with a D/A are almost nil. But those smaller pads and a bit too much enthusiasm (coupled, perhaps, with a lack of understanding) can change things quite a bit. Those of you trying smaller pads for the first time will do well to keep these differences in mind.

But a smaller pad used on a rotary has the opposite effect - again, all else being equal. As pad diameter increases, so does velocity at the outer edge of the pad. Therefore, a 4" diameter pad does not have the same velocity that a 7" or 8" pad will on that tool. Since speed is the primary player in a rotary's ability to do the job (rarely do you use the same pressure on a rotary that you do on a D/A, for example) a larger pad will naturally give more speed than a smaller one, and therefore more cut. That's why, traditionally, pads designed for use on a rotary tend to be in the 8" range while D/A pads tended to be smaller - 5.5" to 6.5".

[Junkman2008]

Re: Is the Dual-Action Polisher Safe?

... But a smaller pad used on a rotary has the opposite effect - again, all else being equal. As pad diameter increases, so does velocity at the outer edge of the pad. Therefore, a 4" diameter pad does not have the same velocity that a 7" or 8" pad will on that tool. Since speed is the primary player in a rotary's ability to do the job (rarely do you use the same pressure on a rotary that you do on a D/A, for example) a larger pad will naturally give more speed than a smaller one, and therefore more cut. That's why, traditionally, pads designed for use on a rotary tend to be in the 8" range while D/A pads tended to be smaller - 5.5" to 6.5".

This logically makes sense. Here's where the technique I teach avoids this scenario. If one never turns the PC past a speed setting of 5 and only uses 9-14 pounds of pressure, it will be a non-issues. The polisher works for you. But you're right, if the user lays the "gorilla grip" on the polisher, there's no telling what damage might happen.

[TimG]

Re: Is the Dual-Action Polisher Safe?

Good video indeed!

[Peter.kelly]

Re: Is the Dual-Action Polisher Safe?

Wow! Thanks to all for the clarifications. To be honest, I've been doing cars by hand (mostly) for 35 years (17rs old to 52) and the fun of rubbing a car by hand for a few hours is somewhat diminished. It typically takes a few years to complete the full car as it's a hobby. There is a big bang in working on getting a car looking good after getting it mechanically good. By hand, this will take on the order of 96 hours of hard work on a medium sized car. If this lightens the load - and I think it will, I'll give it a try. One thing for sure - a restored car has a higher gloss and shine than it did when it rolled off the factory floor! Bring on tomorrow's innovations!

[Junkman2008]

Re: Is the Dual-Action Polisher Safe?

Man Peter, you're a better man than I. There's no way I would do this stuff by hand. My ball & socket joints hurt for three months after the first time I clayed my car. I use a lot more pressure than anyone else I seen clay. I thought I was going to have to have an operation! I couldn't imagine doing paint correction by hand. After seeing a demo from the guy who use to represent Meguiar's, I had no desire to go through that sweat tank!

[TH0001]

Re: Is the Dual-Action Polisher Safe?

Believe it or not, I have found that to not be an issue with the focal pads and the PC, even with the more powerful PC-7424XP. Because of the built in clutch with the PC, the pads will slow down significantly as you apply pressure. I use these a lot around emblems and wicked contours of various cars and have not seen any issues at all. Because of the design of the PC, these pads are very friendly to the paint.

These pads are marketed to be used on a drill for spot repairs but I don't advise anyone do that. As you know, a drill is going to reproduce the action of a true rotary and the opportunity for a catastrophe is 10-fold compared to the PC.

Thanks for the welcome!

There is no clutch or anything that resembles a clutch on a Porter Cable (or any random orbital that I am aware of).

[Junkman2008]

Re: Is the Dual-Action Polisher Safe?

There is no clutch or anything that resembles a clutch on a Porter Cable (or any random orbital that I am aware of).

Then explain why as you add pressure to the PC, the rotation of the pad decreases? The orbital action continues but the rotation speed of the pad is totally dependant upon the pressure you apply. That is a clutched action.

[Mike Phillips]

Re: Is the Dual-Action Polisher Safe?

There is no clutch or anything that resembles a clutch on a Porter Cable (or any random orbital that I am aware of).

I remember this controversy, in fact I ended up writing an article about it and in the article I gave full credit to the person that finally tracked down the EXACT terminonlgy... it's called...

The Free Floating Spindle Assembly


I wrote an article about this and have posted it to the "Hot Topics" forum, if it's approved it will be there today and it explains the whole story about the mechanism unique to DA Polishers.

[Michael Stoops]

Re: Is the Dual-Action Polisher Safe?

This logically makes sense. Here's where the technique I teach avoids this scenario. If one never turns the PC past a speed setting of 5 and only uses 9-14 pounds of pressure, it will be a non-issues. The polisher works for you. But you're right, if the user lays the "gorilla grip" on the polisher, there's no telling what damage might happen.

This is absolutely spot on, but please allow me to reiterate a very important point you make here:

If one never turns the PC past a speed setting of 5 and only uses 9-14 pounds of pressure, it will be a non-issues.

For anyone new to using smaller pads on a D/A, please take this advice to heart. The potential problem with new users is that they've read online, repeatedly, that "the D/A polisher is totally safe and you can't do any damage to the paint with one". They take that as gospel, and then they get crazy.

But you're right, if the user lays the "gorilla grip" on the polisher, there's no telling what damage might happen.

Unfortunately, this is what too many new users do after being lulled into a false sense of security.

We just wanted to stress this point - respect the tool, understand the dynamics of what's going on, and use your brain when working on paint. Stop. Observe. Evaluate. Think. Of all the tools you have available to you when working on your car, your brain is by far the most important. But too many people fail to utilize it fully.

[Junkman2008]

Re: Is the Dual-Action Polisher Safe?

I remember this controversy, in fact I ended up writing an article about it and in the article I gave full credit to the person that finally tracked down the EXACT terminonlgy... it's called...

The Free Floating Spindle Assembly

Thanks for clearing up the technical name for it. I will call it by it's correct name, although it basically acts as a clutched device. If I say clutched, people will understand a lot quicker as to what I'm talking about. The Free Floating Spindle Assembly will need a little more explanation!

...We just wanted to stress this point - respect the tool, understand the dynamics of what's going on, and use your brain when working on paint. Stop. Observe. Evaluate. Think. Of all the tools you have available to you when working on your car, your brain is by far the most important. But too many people fail to utilize it fully.

I like this. Spot on.

[Mike Phillips]

Re: Is the Dual-Action Polisher Safe?

Thanks for clearing up the technical name for it. I will call it by it's correct name, although it basically acts as a clutched device.

The resulting action is similar to the resulting action of a clutch mechanism, anyone that's owned a Mini Bike with a horizontal shaft lawn mower motor which uses a centrifugal clutch will probably understand

If I say clutched, people will understand a lot quicker as to what I'm talking about.

Exactly... the goal being to help people understand the tool is safe while focusing on the major topic... polishing paint, not the internal workings of a tool... been there, done that...

Now days in my classes I pass all the tools we cover in the class around with no backing plate and show everyone how the drive mechanisms work and by doing this they have a better understanding of what's going on when the backing plate and pad is on the tool and they're operating it.

It's the idea of helping people to understand why they're doing something not just what to do and understanding how the different drive mechanisms of the different electrical polishers work aids in this area of education .

The Free Floating Spindle Assembly will need a little more explanation!

Just share the link to the article, it's now a blue clickable link...


And here's the article...

The Free Floating Spindle Assembly - The Story Behind The Story... by Mike Phillips

Keep up the good work Junkman!

[TH0001]

Re: Is the Dual-Action Polisher Safe?

Then explain why as you add pressure to the PC, the rotation of the pad decreases? The orbital action continues but the rotation speed of the pad is totally dependent upon the pressure you apply. That is a clutched action.

This is a great question and a concept that is misunderstood by paint polishers of all levels! From the novice enthusiast, to the guy who polishes a couple of cars a year, to the avid professional. I respect your willingness to help people and am honored to have the same opportunity to educate.

You didn't say clutched action, you said clutch.

Because of the built in clutch with the PC

This statement insinuates there is some device that is used to transfer the orbital motion of the machine directly into the rotational movement of the pad, and this is not true.

As Mike noted, there is a spindle assembly that allows the pad to rotate freely in the housing (minus the drag from the bearing in the assembly), but it's action bears no resemblance to any clutch, no more then the ball and socket joint of your shoulder does.

Then explain why as you add pressure to the PC, the rotation of the pad decreases?

To understand why it slows down, we first have to have a grasp on what makes start rotating in the first place. As the pad orbits quickly, centrifugal force causes the pad to start spinning in the same direction as the orbit. There is no direct link (clutch) that causes this to happen, it is just physics. Perhaps an easy way to grasp this is to imagine holding a string with a ball tied around to one end. If you want to make the ball swing around you (rotate) you hold the string above your head and start orbiting your arm.

As your orbit your arm (unless you are Linda Blair from The Exorcist and can detach your wrist and actually spin your hand 360 degrees) the ball and string will begin to rotate in the same direction. So now we have small orbital motions (jiggling your wrist around) beginning transferred into rotational motion with out the use of any clutches (this is the best example I can think of to explain why the pad rotates, and probably the most applicable).

If we add friction to the string (by replacing the relatively aerodynamic ball with a note book, creating an air brake) the rotation of the pad will slow considerably. You will have to orbit much faster to maintain the same movement. Again we have nothing working like a clutch, we just have physics that are so universal we never stop to think about them.

The reason the pad slows down (considerably) is because there is no clutch that directly transfers the orbital motion of the machine to the spinning action of the pad. In fact the term 'Free Spinning Spindle Assembly' is perfect, as it is Free Spinning.

[Fly Bye]

Re: Is the Dual-Action Polisher Safe?


I'll throw in my .02 cents:

What causes the Porter Cable to orbit, is an eccentric part, in which the spindle/bearing assembly is fixed to. Because the spindle is fixed offset to this eccentric part, (referred to as an Eccentric HSG kit by Porter Cable) the spindle moves in small orbits when the power is turned on. Because the spindle is fixed to this eccentric piece via a sealed bearing, when the machine is turned on, the spindle not only orbiits, but also rotates due to centrifugal force created by the spindle being fixed slightly offset (via bearing) from the center of the machines rotation.

Although the Porter Cable works sort of like a clutch, it in fact does not have a clutch at all. The rotation is based solely on centrifugal force. A clutch is a mechanism that connects two shafts together, so that they are locked together, and thus spin at the same speed (engaged), or (disengaged) and spin at different speeds.

The backing plate on a PC is never locked, not even remotely close to being locked. The PC orbits in between 2,500-6,800 orbits per minute. If you look at the black dot on the backing plate in the Junkmans video, you'll see that it spins just a fraction of what the machine is turning itself. (the eccentric piece)

Nice video Junkman, kind of entertaining



Peace out

[TH0001]

Re: Is the Dual-Action Polisher Safe?

Although the Porter Cable works sort of like a clutch, it in fact does not have a clutch at all. The rotation is based solely on centrifugal force. A clutch is a mechanism that connects two shafts together, so that they are locked together, and thus spin at the same speed (engaged), or (disengaged) and spin at different speeds.

100% correct. The Free Floating Spindle Assembly is actually the exact opposite of a clutch, which is as you noted, a device that provides some sort of mechanical link to transfer energy (in the forum of motion) between two devices that can be engaged or disengaged progressively.

The only way that there is any type of clutch like action is that if the clutch was fully disengaged vs. the constant free floating action of a DA. However, at which point why even have a clutch?

I personally think distinctions like this are necessary to protect against the misinformation that it is often represented as expert advice so common on the internet.

The backing plate on a PC is never locked, not even remotely close to being locked.

Again correct. Any clutch like mechanism would be counterproductive to the limited power in a dual-action polisher. In fact you can replicate the exact action of a 'locked' backing plate on a DA by using a rotary polisher. Instead of centering the pad on the rotary, offset it 5/32's of an inch. This creates the same pattern as a dual-action polisher with a 5/16th's stroke that has a locked backing plate. You have one rotation per orbit. This creates a lot more friction being transferred to the drive mechanism, which would bog the machine greatly.