Newbie Polishing/Machine Finishing Questions

[nyjetfan]

Hey All - New here around these parts, and wanted to ask a couple of questions about machine polishing/buffing. Sorry if these are covered somewhere, but I haven't been able to find them with the search function.

Some of these probably stem from high school when I was given the task to buff out a car (25 years ago) and my training was "Here's the buffer, there's the car, get to work". Needless to say flat panels looked pretty decent, body contours varied, and the "valleys" between the rear quarter panels and the trunk showed some nice burn marks..

For these questions, assume I'd be using a new Dual Action machine (PC, GG or similar). Haven't purchased one yet, but wanted to build up my knowledge/confidence that I can improve upon my past efforts (and prevent myself from creating issues like I had in the past). There are plenty of informative threads on the different models, so unless there's something specific to a model that would help here, no need to rehash that.

1. Do I have to avoid the body lines on the car? For example, most hoods have a "center section" that is at a slightly different elevation than the outsides. For example, look at the mercedes in the link below - there are "valleys" on the outside of the hood (dips down over the headlights and then rises again above the grill), and I know the orbital I used in HS created some burn marks in those types of environments.
http://www.autogeekonline.net/forum/how-articles/31000-how-remove-sprinkler-water-spots.html

2. Will I need to avoid edges of the body panels, for example the line where the hood and fender meet?

3. What about the sharp body lines - for example where the fender goes from being horizontal near the hood and turns down to create the wheel well. Some cars have pretty sharp angle/turn here which would create a protruding edge - any special considerations there with the machine?

4. Any best ways to learn the technique, other than doing it? I'd definitely start with my 2004 Expedition which can use some correction, and would be very leery of jumping to my Jet Black BMW X3 anytime soon.

Also, if there's any additional input/advice you can offer for a newbie, please pass it along as I'm interested to learn and research now in hopes to prevent a "Oh $h1t, I just...." thread later :-)

[tuscarora dave]

Welcome to the site.

I wouldn't be concerned on the hood around the headlights on that Benz because those lines are very curvaceous, not anywhere near being sharp lines. If using a rotary polisher (and I did read and understand your post) I'd go a little slower in those areas. At worst a PC or GG DA polisher will lose pad rotation in those areas and just jiggle around causing no harm at all. If I were limited to just one DA machine such as a PC or GG, I'd have a 3-3/4" backing plate on hand to work those areas with a 4" pad to keep pad rotation and correction more efficient in those areas.

As for the lines or gaps between panels... I work right up to the edge with DA polishers. To work over that gap, (polishing both fender and door for example) with a DA wouldn't really risk burning the edges so much as it would likely leave you with a boat load of compound / polish splattered all up in the gap and inner fender / door jamb to clean up in the end of the job. That mess can be difficult to clean up and just doesn't have to happen. Could a DA burn the edges between a door and a fender? I guess it could happen if you were working that area for a long time with a real abrasive compound, but it's unlikely with a DA. Rotary would zip the paint off of those edges in a jiffy if you weren't very careful.

The sharp lines around fender wheel arches... you should tread lightly at a minimum around these areas. A $0.02 piece of painter's tape on these sharp edges could save you hundreds for a respray of a burned panel, not to mention the "Walk of Shame" as you go knock on the customer's door and tell them that their pride and joy now has to go to a body shop and have a fender repainted. Tape is cheap insurance against burns and newbie mistakes.

[nyjetfan]

Thanks Dave - Appreciate the detailed response and suggestions to help keep things from going south with the polisher.

[tuscarora dave]

Thanks Dave - Appreciate the detailed response and suggestions to help keep things from going south with the polisher.

Sure thing man!!

With the abrasive technology and the technology, R&D put into the dual action polishers out today and the internet forums for detailing / polishing automotive paint, once you get really good with a DA polisher there isn't much need for the rotary polishers any more if you're not doing a ton of production work.

I'll never get rid of my rotaries but I rarely reach for them anymore either.