Porter Cable XP Sanding & Kevin Brown Method

[David Fermani]

I’ve been wanting to try out some DA sanding with my new Porter Cable XP and test the infamous Kevin Brown Method to remove the marring. I’ve been faithfully using the KBM for a few months and love the way it carefully levels paint and creates substantial amounts of gloss all in one. I’ve heard some people warn of electrocution using water with an electric DA, some say that the PC’s throw is too long. I thought I’d give it try on a complete detail scheduled on this 04 Saab 9-3 and who's paint was in very poor shape. The owner was seriously considering repainting it and gave me the go ahead to do whatever I wanted to the paint.

Befores:






I really wanted to use 3M 1500 Trizact, but realized I only had regular 1500 grit. I had did have a bunch of 3000 Trizact so I felt confident that any heavy sanding marks from the non-Trizact 1500 would easily be refined by following with 3000.



After carefully prepping the surface to insure that all topical contaminants were removed to facilitate safer sanding, I taped the edges with 3M ¾ inch painter’s tape. I wanted to stay as far away from the edges as possible to avoid strike through.

I then lubed the surface with an ONR clay lube mixture:



And then some lube on the sandpaper. I chose to do this wet, but it can also be done dry.



Set the speed between 3 & 4:



Final sanded = 1500 >>> 3000 Trizact:





Initial priming of the LC/CMA Orange Flat pad with Meg’s M105:








1 pass with M105 cleaned up all the sand scratches & left the finish with a decent amount of gloss. (I was able to work ½ the trunk in 1 pass)












Sun Shots after 105. Definitely pad micromarring, but not bad results after 1 easy pass.






Here’s after Meg’s 205 via LC/CMA White Flat pad:

[Jakerooni]

Lookin top notch There Dave.. Makes me want to go out and get some disc paper for the D/A would make it much easier than a sanding block I currently have. How did the owner react when he saw it?

[**Frank**]

Lookin top notch There Dave.. Makes me want to go out and get some disc paper for the D/A would make it much easier than a sanding block I currently have. How did the owner react when he saw it?

x2

Damn, that looks awesome.

[David Fermani]

Lookin top notch There Dave.. Makes me want to go out and get some disc paper for the D/A would make it much easier than a sanding block I currently have. How did the owner react when he saw it?

Thanks Jake - He absolutely loved it!

x2

Damn, that looks awesome.

Thanks Frank!

[the_invisible]

Looks really good!

I have successfully removed sanding marks with the orange pad and M105 on the DAXP on OEM paint as well. One or two cynical skeptics harassed me for the sinful act of removing sanding marks with the DA + foam pad. Nevertheless, your result turns out really good, as expected from the KBM!

The orbital range of the PC, or Griot's, G110 for that matter, are a little long compared to dedicated air powered sanding tools. I will have to give my DA a try for wetsanding.

[gmblack3]

Very nice David! Have you tried any of the surbuf pads yet?

You should prime the entire face of the pad.

[Barry Theal]

David very nice! Have you tried this before sanding with a older pc7424? Also did you use an interface pad for sanding or did you just go with a standard backing plate and paper?

[Leadfootluke]

Very cool! I don't have the balls to do that, haha. But now that I see the results, looks like a great idea.

[David Fermani]

Looks really good!

I have successfully removed sanding marks with the orange pad and M105 on the DAXP on OEM paint as well. One or two cynical skeptics harassed me for the sinful act of removing sanding marks with the DA + foam pad. Nevertheless, your result turns out really good, as expected from the KBM!

The orbital range of the PC, or Griot's, G110 for that matter, are a little long compared to dedicated air powered sanding tools. I will have to give my DA a try for wetsanding.

Thanks invisible!

Very nice David! Have you tried any of the surbuf pads yet?

You should prime the entire face of the pad.

Thanks Bryan! Nope, the SurBufs are at the top of my list. Also, thanks for the advice. I never thought about doing that. I always figured that the initial loose polish gets sucked into the center of the pad and didn't need to prime that area. I'll make sure to correct it (pun intended).

David very nice! Have you tried this before sanding with a older pc7424? Also did you use an interface pad for sanding or did you just go with a standard backing plate and paper?

Thanks Barry! No, this is the 1st time sanding with a PC. I used the LC yellow 6 inch plate (stiff). I made sure to start and stop the machine while it was totally flat on the surface to avoid pigtails. I 1st tried speed 2.5, but it wasn't keeping up with my ~slow surface movement.

Very cool! I don't have the balls to do that, haha. But now that I see the results, looks like a great idea.

Thanks Leadfootluke! - No big deal - just try it on a scrap panel (or a friend's car ) 1st.

[Barry Theal]

ok damn I was looking for a comparison between the two machines. I use my pc a lot to sand. i just get tired of the air running a lot. I just bought the makita 6040 which is a d/a And a random orbitol. I'm gonna give it a try with sanding. I got a 1960 MG that will be completly sanded. I'm wondering how I"m gonna go about it. Any nice work bud! Ill call ya later this week some evening about that pm.

[Kevin Brown]

WOW!

While I am not surprised, I still get a big smile when I see results like this. Very nice job on the priming, too. I reckon you would agree that the key to success on this job was THOROUGH final sanding.

It is great to watch a seasoned pro such as you David take on a challenge such as this and use an unorthodox procedure. The results speak for themselves.

[Kevin Brown]

...
The orbital range of the PC, or Griot's, G110 for that matter, are a little long compared to dedicated air powered sanding tools...

Not to jack this thread, but this is a common misconception, my man. You are a guy that is not afraid to try or learn new things, so bear with me on this.

I agree that most of us correlate fine sanding with the need for a small stroke machine, but after much thought as to why this would be true, I deduced that is is NOT true. My opinion, yes, but it is backed up with a lot of thought (and a decent amount of experience).

I also chatted with a few guys on this very topic over the past year (whenever it was on my mind). It was especially helpful to talk to those that had zero experience with sanding (they were just good thinkers). No bias towards large or small stroke. Then, the thought process began.

Bottom line for me? Unless I need to use a machine in a tight area that does not allow safe use of a long stroke machine... or I need a machine to be used on a surface that requires precise control, I will opt for the large stroke machine every time.

There are many reasons for this, but one of the biggest reasons is obvious if taken to an extreme. First, eliminate the random rotation of the backing plate (which is driven by centripetal force, but more on that in a bit). Imagine a machine that only created a 1/128th-inch stroke, and we are using a six-inch sanding disc. The machine's miniscule movement would essentially bore tiny little holes in the paint, and any abraded paint material would probably not move away from the abrasive particle, so we would likely see pig-tailing as the abraded paint residue packed itself around the individual sanding grains.

Now, switch to a machine touting a two-inch stroke. Obviously, the stroke on this machine would not allow for safe use in a confined area because the backing plate's side could bash into surrounding parts. Plus, the area being sanded will be larger (effectively an 8-inch diameter area versus an area of 6-1/128th inch for the small stroke machine).

But- if the sanding disc is durable and high quality (in terms of particle size and distribution), the sanding will still be thorough. The speed of the particle's movement per oscillation will be higher, so cutting power increases, as does the distance each particle moves. This increases the likelihood that the abraded paint will eventually migrate away from the abrasive grain that removed it in the first place. Lots of lateral movement, so there is a high likelihood that the residue (and any sanding grains that have detached from the disc) will not become trapped under the disc.

I could go on and on, but won't right now. As for the random rotation of the backing plate... all other parameters being equal, the rotation will be higher because more movement creates more centripetal force.

THUMBS UP AGAIN, DAVID!



p.s.-
From what I know, 3M has recently decided to recommend a 5/16" stroke for use with their sanding discs.

Posted this diagram up a while back. Hope it helps.