PC & WetSanding?

J

Jeremy1026

New member
Does the PC pack enough of a punch to take out the marks left over from wetsanding? If a PC can remove it, would a 4in cutting pad with an abrasive polish, followed by a 6in mid-level pad with a semi-abrasive polish be enough to remove the wet sanding marks?
 
Some will disagree, but you can get the job done with a PC after using 2000 grit. It takes 4 or 5 passes with a heavy cut compound (again, I know, not supposed to do with a PC... blah blah). Definately a time waster for a pro, but do-able.



mr2_wetsand.jpg




The left side was wet sanded with 1000, then 2000, then #84x4-5 passes, #83, followed by #82. Its hard to tell in the picture, but the reflection of the bulbs on the right is very blury and the one on the left is much more defined and clear.
 
yeah its possible, but a rotary with a wool pad will clean it up 10times faster



via PC:

hi temp extreme cut, or menzerna powergloss with a megs burgandy or LC yellow pad, 3-4 passes, then megs 83 with a lc orange 2 passes, then a light polish with a heavy polishing pad, then light polish with a light polish pad will leave you with some good results...but will take about 10times as long....
 
I've got a question about finishing out wetsanding marks that I *hope* relates:

Which process is better(removes less clear/paint) after you have wetsanded with your final paper(2000,3000,4000w/e)-

PC w/ heavy compound i.e. HTEC and making many passes with pressure



Rotary with whatever process you would use on a rotary?

Sorry if it's too far OT.
 
I am going to say that 2000 grit is IMPOSSIBLE to remove with a PC. You might reduce the sanding marks but they are still there. On my NBM paint some 2000 grit marks remain after using OHC/wool pad on a rotary. They are only visible under lights at night or bright direct sunlight but they are still there. 2500 or 3000 would be a better choice if working with a PC.
 
A PC or UDM will remove 2000 or 2500 grit sanding marks with an Orange LC pad and Prima Cut polishing compound. I do this infact on the show cars that I finish for the shop that I rent from. I do most of the work with the rotary but on portions that are difficult to access or subject to burning, the PC or UDM work fine. They are slower and less thorough though, but definitely possible.



I think the myth about the PC not being able to remove sanding marks began with Meguiars. With their pads and polishes, it's not possible, but choosing a different system is all it takes.



Richard
 
wannafbody said:
I am going to say that 2000 grit is IMPOSSIBLE to remove with a PC. You might reduce the sanding marks but they are still there. On my NBM paint some 2000 grit marks remain after using OHC/wool pad on a rotary. They are only visible under lights at night or bright direct sunlight but they are still there. 2500 or 3000 would be a better choice if working with a PC.
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How is it impossible to remove with a PC? Sure it takes more time than with the rotary, but the last time I heard, an abrasive is an abrasive, and the longer you use it, the further it goes down in the paint. In fact if you keep going with 84 on an maroon pad, you will get down to sheet metal. So unless you subscribe to some magical theory about melting the paint smooth, I don't see how you can believe that.



The only thing I can think of, is you are sanding incorrectly and getting lots of tracers. Those are a bear to remove with anything as they go deep.
 
OctaneGuy said:
I think the myth about the PC not being able to remove sanding marks began with Meguiars. With their pads and polishes, it's not possible, but choosing a different system is all it takes.



Richard
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Thanks for backing me up. It is a myth.
 
Hope you don't mind, I shot a little video on the UDM vs. PC yesterday, and here are some still shots from the footage showing how well the PC and UDM can remove sanding marks on a painted/sanded hood. These were little areas masked off with painters tape that were polished out using Prima Cut and the 6" LC Orange Pad. The light and the towel were placed there to see the quality of the finish after the quick buffing. Had I spent more time, the results could have been even better.



The results were actually identical with one minute of polishing using the same pad and chemical on speed 6. I also measured the before and after temperatures and nothing substantial, only a few degree difference. It takes much longer than a minute to heat things up with this combination.



On this same panel, not visible in these shots, I used the rotary with a W7006 cutting pad and M84 compound to remove the sanding marks. So I was able to compare the results of the rotary to using the PC/UDM.



pcwetsand1.jpg




pcwetsand2.jpg




pcwetsand3.jpg


yakky said:
Thanks for backing me up. It is a myth.
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Hard to say. I'm using the UDM nearly every day for the past two weeks. It's a different machine over the PC for sure, however the pad makes a huge difference. Whether you use the UDM or the PC with the 6" pad that it comes with--vibration is greatly reduced over the usual 6.5" pads. I find that I'm able to spin dry pads that I've washed with the UDM, which I can't do with the PC.



I've gotten paint panels hot enough to say OUCH with the UDM--similar hotness levels to the rotary.



Aside from the minor quirks the UDM has--several of which I've solved by taking mine apart and modifying it--I definitely like the UDM over the PC as a tool to complement my rotary buffer and at times as an RB replacement on delicate paints.



Richard



ZoranC said:
Richard, from your experience so far with the UDM, how much more aggressive than PC you would say it is?
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Richard, thank you for the input! I'm glad you kept an open mind regarding UDM ;)



Would you mind sharing with us, please, which quirks you addressed and how? My biggest complaint is size of shroud that is not always letting me get under mirrors.
 
Well, the short cord is easily fixed, by a trip to the hardware store and purchasing a longer cord which is sold by the foot. If you're 5'7 or shorter, the existing cord length is fine, but if you're 5'11 like me, the cord connector when thrown over your shoulder hangs above the ground and is annoying.



I'm about 5'11

udmrickshort.jpg




Jay is about 5'7

udmjay1.jpg




The variable speed dial is upside down when compared to the PC. Although I haven't flipped mine yet, when I disassembled my UDM yesterday, I noticed that it's easily flipped..although the wires might need to be lengthened slightly--not hard if you're decent with a soldering iron.



The sensitive switch is annoying, but worst thing about it to me is there is no visual indication of whether it's on or not. What I wanted is the ability to see at a glance the state of the power switch, so with some drilling of the housing and some red cardboard, I made a visual indicator so that I can see at a glance if the power switch is on or not. This makes it easier when plugging in the UDM that it's not accidentally on. Part of the problem is with the shorter cord, the UDM was getting disconnected prematurely a lot, so being able to know for sure whether the UDM was in the ON or OFF stage was critical for me. I PM'd DavidB about this mod, not sure if he will want to implement it or not in future models.



The larger protective housing isn't much of a problem to me. It's about 1.5" inches larger and about 1/4" taller than the PC. I know this based on the PC Guard that I installed on my UDM--yes a UDM Guard or Ultimate Guard will be available soon.



People have complained about the vibration, but I've found that to be a problem only on pads where the velcro backing isn't sticking well to the backing plate. With a new pad that was centered properly, vibration wasn't an issue. With a worn pad, vibration was more problematic. But with the 6" pad most of the issue went away--but this was true whether I used the PC or the UDM.



I documented this stuff in a little video I will be posting online next week or so comparing the UDM and PC.



Richard





ZoranC said:
Richard, thank you for the input! I'm glad you kept an open mind regarding UDM ;)



Would you mind sharing with us, please, which quirks you addressed and how? My biggest complaint is size of shroud that is not always letting me get under mirrors.
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Richard, thank you once again!



OctaneGuy said:
If you're 5'7 or shorter, the existing cord length is fine, but if you're 5'11 like me, the cord connector when thrown over your shoulder hangs above the ground and is annoying.
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rkf76, are you listening?



OctaneGuy said:
The larger protective housing isn't much of a problem to me.
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I really dislike it.
 
You're welcome. I guess the larger housing hasn't been much of a problem because I haven't had too many areas lately that I couldn't reach with the UDM. Time will tell of course, and likely what will happen is that I will pick up one of my PC's if I run into issues.



But with the backing plate off, it's obvious how much space there is around the counterweight (whereas the housing nearly hugs the PC counterweight), and unless it's large for some reason that I don't know--it does seem unnecessarily large.



udmpc.jpg




ZoranC said:
Richard, thank you once again!





rkf76, are you listening?





I really dislike it.
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I used a Megs flexible sanding block and I did get some tracers. Chances are most inexperienced wetsanders will get some. I still don't think it's good advice to recomend removing 2000 grit wetsanding marks with a PC. On hard clears a PC just doesn't have the power to really correct paint. Compare one side of a flat hood compounded with a rotary with wool followed by a polish with foam followed by a finishing polish and PC in contrast to the other side done soley with a PC. After viewing from all directions you will notice that the side done with a rotary will have a gloss that the PC side isn't capable of producing. Also results will vary based on the cars color. A dark metallic will show stuff in bright sunlight that you won't ever see on lighter colors.
 
It's pretty simple. It all boils down to what system you are using with the PC. In my experience, I've polished out 2500 grit Unigrit with the PC using the Prima system and an orange LC pad. If I'm going to buff out an entire car, my preference is always with the rotary with either a cutting pad and compound or a wool pad over a PC with any system. But I don't think anyone that is considering wetsanding and polishing will attack an entire car with a PC. Not something I'd recommend anyways. But for spot sanding of touchups, or small repairs, or as in my case, removing the sanding marks on delicate paint areas, the PC or even better--UDM-- is a safe and viable option with the right system.



wannafbody said:
I used a Megs flexible sanding block and I did get some tracers. Chances are most inexperienced wetsanders will get some. I still don't think it's good advice to recomend removing 2000 grit wetsanding marks with a PC. On hard clears a PC just doesn't have the power to really correct paint. Compare one side of a flat hood compounded with a rotary with wool followed by a polish with foam followed by a finishing polish and PC in contrast to the other side done soley with a PC. After viewing from all directions you will notice that the side done with a rotary will have a gloss that the PC side isn't capable of producing. Also results will vary based on the cars color. A dark metallic will show stuff in bright sunlight that you won't ever see on lighter colors.
Click to expand...
 
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