This is how the PC really works

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Grimm

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There was a thread several weeks ago where someone was concerned because their PC was not spinning after some pressure. This led into a debate amongst a few of us on how the PC 7424/7336 really works. Some are under the misconception that the machine actually is supposed to spin the pad on a single axis like a rotary, or else it is faulty. I emailed Dewalt to ask about how the machine really works, and finally after several weeks I actually got a reply:

Subject Please clarify function of the 7424/7336 Discussion Thread Response (Stacie)03/14/2007 10:38 AM Dear Doug,

The term "random orbit" means the disk moves out of the plane line of the motor. The pad is not connected directly to the motor. The rpm of the pad on a flat surface is 1 to 300 RPM. it is possible there will be no rotation and/or the rotation can be in either direction. This makes the sander much more aggressive than non random orbit sanders without creating the swirl marks one would expect with disc sanders.

One misconception of the 7424 is that it is not a buffer. It is an applicator of the wax/polisher and mimics the swirl motion of your hand while applying product.

Regards,
End User Services
 
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I dunno... I think it is. its not officially a buffer as it wasnt meant to be.

but:

IM001158.jpg
 
Well, technically, it started out life as a random orbit sander. You could take the sander with the velcro pad and then put any velcro buffing pad on it. For that matter, you could buy any random orbit sander from Lowes, Sears, or Home Depot and slap a polishing pad on it and it would work.

I think totoland uses a Festool "random orbit" sander...pretty much the creme de la creme of sanders.
 
BTW, it's the random orbit nature of the machine that helps to prevent it from generating so much heat on one spot and burning the paint.
 
the pc's original use was for furniture and wood finishing...i used to use them when I made tables and cabinets...FINISH sanding was its main duty as it could do 3000 oscillation to my 2-3 hundred...and it did a great job of buffing and burnishing waxes and stains on flat table tops...the car enthusiat crowd picked up on the pc and then started designing/creating/modifying wool and then eventually foam pads to be used with the pc...
 
nick19 said:
These polishers are characterized by the motion of the head. It spins on a central spindle, but unlike a rotary polisher, this spindle rotates around an eccentric offset. On a PC, this produces a jiggling motion. This irregular motion prevents the polisher from burning the paint, which refers to removal of paint below the clear coat surface. Dual action polishers are very USER FRIENDLY as a result of this feature.

The same safety feature which reduces the possibility of damage from a PC also prevents it from removing deep scratches. While a PC will improve the appearance of scratches and remove light swirls, it cannot cut or damage the paint.

If you need more thorough scratch removal, this will require a rotary. Keep in mind, rotary polishers in inexperienced hands can damage the clear coat and run the risk of a serious PAINT BURN. A rotary polisher SHOULD NOT be used by a novice.

On the plus side, dual action polishers will improve the texture and luster of automotive paint with minimal risk.




Hope this helps...




-Nick :cheers:
Click to expand...



From another I posted about... this is in simplest terms what the PC is and how it works.
 
Well technically I suppose the PC isn't a polisher. Considering how much effort it requires compared to a rotary, it's sort of like using a sander to plane a board instead of a planer. Eventually you can do it, but it will take longer, more work, and you might not be totally satisfied with the results. ;)
 
oh dogshit, it removes any swirls that I have, so as far as I'm concerned, it's a polisher.
 
Thanks for doing the legwork and sharing with us Doug. Interesting stuff. Tough to picture what Dewalt means by "more agressive".
 
and/or the rotation can be in either direction.

This is the first I have seen any official comment on reverse spinning. No one on this or the Meguiar's Forum had heard of it. I contacted the manufacturer by E-Mail, and they played dumb.

I feel liberated.
 
orngez said:
the pc's original use was for furniture and wood finishing...i used to use them when I made tables and cabinets...FINISH sanding was its main duty as it could do 3000 oscillation to my 2-3 hundred...and it did a great job of buffing and burnishing waxes and stains on flat table tops...the car enthusiat crowd picked up on the pc and then started designing/creating/modifying wool and then eventually foam pads to be used with the pc...
Click to expand...

It does suck doing it by hand I wish i had my Pc when i made my table!
 
Can you use a PC to buff the wax and if so is it any better than by hand ?
 
Man looks like the story of the PC is a very interesting one. Thanks for posting this info, really nice of you to do all the re-search and share. To be honest, I don't miss the PC...I like the Cyclo and the rotary.
 
Im lost ... first the 7424/7336 is a Porter Cable device. So why not contact them or Black/Decker which recently bought them. I am lost as to how Dewalt came into this, and does Dewalt even make a random orbital polisher and not just a sander ??
 
Killr, I saw your comment, and was confused because I did contact Porter Cable. But I looked at the email I still have from them, and it was a Dewalt address. I looked it up, and Black & Decker owns both Dewalt and Porter Cable. Why the Dewalt address I'm not sure.
 
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A rotary is nothing more then a varible speed sander or grinder. What makes it a polisher is putting a polishing pad on it instead or a grinding disk or a backing plate with sandpaper. Sanding a piece of wood to get the scraches (cut marks out of it) is really not mush different then polishing the paint on your car. It does not matter what something was initially designed for or called. Lots of tools have many uses. Both a PC and a rotary can be used as a polisher. They can also both be used to sand a piece of wood and many other uses. Both also have advantages and disadvantages as a polisher over the other. Use what works best for you in the situation you have at hand and your level of skill.
 
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Translate please

So it rotates in either direction, wobbles, etc. But what is its most efficient motion for a specific purpose? When I first started messing with my new PC 7424 it seemed like it wasn't hardly moving at all. Been using it for a year now. In my Neanderthal mindset, I decided that it would polish and buff most efficiently in its "mostly rotary" state. So I marked some radial lines on the backing plate and use the direction and speed of the rotation as a guide to the contact plane. In other words, I want the black lines to rotate counterclockwise at the rpm I have chosen.
Is this correct (for polishing, paint cleaning, and buffing)? Is that the most efficient motion for a random orbital or does it perform those tasks just as well when it meets some resistance and slows down or goes counter-clockwise?

Somewhat unrelated: The 7424 is dubbed a "polisher." It looks just the 7336 "sander." Is there any reason why one could not use it as a sander (for woodworking)?
 
DeWalts "version" is a DW443. Runs a little faster than PC. Cannot change backing plate.
 
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