These grinding and sanding...
These grinding and sanding discs are available in this finishing kit package from 3M. This kit comes with three 2-inch sanding discs and two 2-inch Scotch-Brite discs, which are useful for grinding on rust, old paint, body filler, and primer.
There's more to a good paintjob than good paint. There's the preparation that goes on before the first can of paint is opened; the work that happens in between coats of primer, basecoat, and clear; and the effort that takes place after the shooting stops.
Having the proper abrasive materials and tools is necessary to bring out the best properties of the paint. Any decent auto parts store stocks hundreds of abrasive products and the Internet supplies tens of thousands. How do you decide which fundamental items you need to do a decent job preparing sheetmetal, filler, primer, and paint? We talked to some industry professionals to get their wisdom and advice. Their combined knowledge could fill a library. The following pages just scratch the surface, but scratching the surface is a good start toward a great finish. Thanks to Brett Caslow and Larry Lavigne from 3M, David Kidd from Planet Color/Sherwin-Williams Automotive Finishes, Tom Nicolosi from Gerson, Brad Rathbun from Summit Racing, and Joe Richardson from The Eastwood Company, who provided much of the following information.
Supplies
Sandpaper is the most important and most used abrasive tool. The store shelves are filled with countless sizes, styles, and grits. If you're planning on being involved throughout the painting process, load up on 36-, 80-, 120-, 240-, 320-, and 400-grit dry sheets for early "below the paint" prep work, and 600-, 800-, 1,500-, and 2,000-grit wet-or-dry sandpaper for later "above the paint" wet sanding. You'll also want an assortment of sanding blocks, and a supply of grinding discs and sanding discs in various grits, plus a paint and rust stripper-cleaning wheel for the tough stuff. Post-paintwork will also require the use of various buffing pads, and the liquid products used in the buffing procedures.
Quick-change discs from Summit...
Quick-change discs from Summit Racing were among the abrasive products provided for our Project Shop Truck buildup. These multiple-use discs are available in 2- and 3-inch diameters and a wide selection of grades. The discs on the left are zirconium aluminum oxide, in 24-, 36-, and 50-grade. The others are fibered ceramic; blue is very fine, brown is coarse, and maroon is medium.
There are advantages and disadvantages of power tools. If you're a professional, you're already using power sanders for the sake of efficiency, and your skill level has probably eliminated most of the disadvantages we're about to talk about.
For a lot of hot rodders, this hobby is as much about playing with tools as it is about playing with cars, and the appeal of getting the job done fast is great. But doing the work slowly by hand may be the smarter move. Kidd from Planet Color encourages enthusiasts, especially those with less experience, to take the slow road of hand sanding.
Block sanding a car with a powerful DA (dual action) sander is fast, but it can get you in trouble fast too, either by building up heat and warping sheetmetal or by overaggressive grinding. Unlike working on a computer, bodywork has no "undo" button if you go too far. Going slow forces you to focus on the job, including inspecting the sanding from different angles in different light to check on your progress and spot potential areas where more attention is needed.
The Summit quick-change discs...
The Summit quick-change discs came in handy for grinding down the welds when Hot Rods By Dean patched the gasoline filler hole on our project '47 Chevy pickup.
If you are using power tools, you already have the advantage of speed and power. Don't get greedy by muscling the job, which can cause overheating and wear out discs faster-or cause damage to the sheetmetal. Apply enough pressure to cut, and let the tool do the work.
Below the Paint
The purpose of sanding is to create the best surface for the new paint. At this stage, sanding is accomplishing two things: It's removing the old material that might effect the quality of the new finish going over it, and it's roughing the surface to provide some grip for the next layer-whether it's filler, primer, or paint.