How Much Pressure To Use With A Random Orbital Polisherby Ivan Rajic
Quite a few people have asked me over the years about the correct amount of pressure when using various polishers, especially concerning the Porter Cable 7424 XP. Even with years of experience, this is a very tough question to answer correctly. Reason being, there are numerous variables and goals within a polishing process, which will undoubtedly affect the technique used during the process. Also, different people are stronger or weaker than others, so asking to answer it simply is nearly impossible.
That said, I’ll try to explain it as best as possible in this article without going into too much detail.
What Is The Goal?
I believe the first variable is figuring out exactly what’s to be done on the paint in terms of polishing. Generally speaking, more pressure leads to more correction, but that’s not always the case and that may not always be exactly what you want. It’s not always the case because on certain vehicles, it’s much more efficient to let the polish and pad do the correction by applying only moderate pressure, as opposed to leaning into the pad as you would on many other vehicles. Pad and polish selection, as well as the obvious vehicle in question will determine how much pressure is preferred to do as much correction as possible. On the other hand, it may not be always what you want in certain situations. For example, if you plan on doing only one stage of paint polishing, you surely don’t want to rely on a lot of pressure to correct the paint as it may leave marring that will necessitate a second polishing stage.
What Type Of Paint Is Being Polished?
As mentioned above, different paint will react better or worse to a lot of pressure during polishing. Black, sensitive paint like we see on jet black Porsche, BMW and Subaru for example, will react very poorly to a lot of pressure because this pressure will lead to a lot of left over marring to be corrected with a second polishing stage. In many cases, if you are too aggressive with such paints, you may end up needing a third polishing stage to fully clean up the marring and buffer marks left over from the initial compounding stage. Conversely, paints that are hard to correct, such as those generally on Audi and Mercedes vehicles, react well to a lot of pressure as they tend to correct much better due to the additional pressure. Again though, it all goes back to the question “what is the goal” because when working on a certain paint, you first need to know how many polishing stages will be done before figuring out the process and products to be utilized. Which leads us to the next and final question…
What Type Of Polishing Pads And Products Are Being Used?
Once you know the process and on what vehicle it is to be done, the next step is to determine the products to be used with the polisher. Pressure (heavy or light) doesn’t necessarily come into play only with compounding stages and multi-stage polishing. In general, more pressure is good for compounding stages and light pressure works well with finishing stages, but this greatly varies on what polish and pad is being used. On many paints, using a finishing polish at a slower speed with light pressure will lead to polish/pad induced marring, whereas introducing more pressure will leave a perfect finish. In short, the products and pads will have a big impact on how much pressure is best for the process in question.
All that said, there are general rules that we can always go to as a starting point. As I mentioned above, heavy pressure during compounding works really well when using a random orbital polisher (I find rotary polishers like the speed and not much or a lot of pressure). Light pressure works well during finishing stages where you don’t want to press into the paint much and simply let the pad and polish do the light correcting work. To get a really good gauge of how much pressure is necessary, especially if you’re only working on a few family cars yearly, try some polishing on the vehicle and see what pressure and technique gets the job done best. Then, get a scale and try to replicate that pressure to see at about how many pounds of pressure you need to do the polishing work. Generally speaking, 25-35lbs is good for most correction work when using a random orbital polisher, but it should only be used as a starting point as stated above.
Well I hope this sort of clarifies the question many have been asking and gives everyone a good place to start the experimentation on their vehicles. Thanks as always for reading and please feel free to leave any questions or comments below.
Thanks for the article very useful
Ivan thanks for sharing this info was spot on.
Many greeting from Slovakia!:)
Thank you for useful information.
What is your experience with forced rotation polishing machines (Flex 3401) on soft paint (Toyota, Mazda …). What a pressure and pads are recommended to remove swirls and RIDS?
You say “25-35lbs is good” pressure? Is that right?
What are your thoughts on using shank mounted polishing pads? I would like to use my electric drill.
Thanks for the kind words all.
Jan, I mainly work with the Flex 3401 polisher and the article above completely relates to that machine as well as a random orbital like the Porter Cable. I have no trouble working with soft and sensitive paint with the 3401 so I’d follow the guidelines above as far as pressure goes.
Al, that pressure is a non-scientific measurement I got from a basic bathroom scale. When I tried to replicate the pressure I use during polishing I normally came up between 25 and 35lbs for correction/compounding and less when finishing.
Iceberg, I’ve only tried it a couple times on a headlight polishing kit and didn’t like at all how it felt. It’s much harder to control and you don’t have the necessary weight behind it to use with pressure when correcting paint. From my brief experience, I’m sure it can do a decent job on paint, but it will probably take a lot longer and results will be worse than if done by a proper polisher.
Does the number stated in pounds that you measured on the bathroom scale include the underlying weight of the polisher? This makes a dramatic difference in overall poundage I would believe. Thanks, very helpful!
Daryan, yes and no. Reason I say that is the weight of the polisher really doesn’t come into play much or at all, actually it’s negative in some instances, when working on side/underside of the car’s panels. If you try to check the rough pressure/weight on the scale, make sure you do it normally as if you’re working on the hood (polisher on top of scale and push down) but also place the scale (if possible) against the wall perpendicular to the floor and try to match the same pressure. I noticed many people, some assistants and some students I’ve trained, can correct the upper surfaces well by utilizing pressure (gravity and polisher weight), but get sub par results on the side panels due to the lack of pressure. Hope that helps!
I mark the backing plate with a marker and make sure it’s spinning at all times as I apply more and less pressure. I apply pressure just until the pad starts to slow down and hold the pressure there (pad still spinning fairly quickly 75% speed %25 drag due to pressure).