i bought the porter cable 7336sp same as (7424) but with the sanding pad.i did the hood ,fenders,one door.but when i started on the roof i noticed separation of the black plate to the white pad.was i pushing too hard or is this common? other than that problem this is one bad ace machine!

 

The white pad that comes with the PC isnt very good. I wouldnt use it on my nephews bicycle.
Get a 5inch backing plate and some LC Pads Orange, White and Black

http://www.obsessivedetail.com/Buffer.html
Check out Justin's starter kit. That will get you on the right track.
Orange- Light Cutting
White- Polishing
Black(Grey) Finishing (waxing/sealant/glaze)
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