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View Full Version : Pictures from October 17, 2015 Advanced Class



Michael Stoops
Oct 19th, 2015, 07:51 AM
Our last Advanced Class of 2015!

After the usual classroom instruction portion we head out to the garage for a hands on demo before lunch.
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The Unigrit Sanding Block for spot repair. The large circle drawn in the water represents the area that would have been sanded had a typical sheet of sand paper been used to correct a small defect.
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After using the block, we now draw a small circle inside the big one - this represents the area that must now be buffed out to remove the sanding marks from the block. Remember, the larger circle represents the area that would have been sanded using traditional sandpaper; the required buff out area would be larger still. Why would you sand and buff such a large area when all you're working on is a tiny little spot?
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Hand sanding technique - hand flat on the sanding pad, closely spaced strokes of 6" - 8" in length.
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The E7200 sanding pads are very flexible; use that to your advantage when working on tight radius contours.
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Here we have a uniformly sanded area inside a contour. The small area at the lower right of the sanded patch is what happens when you use the full sanding pad lengthwise into a contour like this, as it lifts away from the bottom of the contour and doesn't work against the surface at all. Worse, the sand paper actually works more aggressively against the area it does touch, and you end up with very uneven sanding.... and a very uneven finish.
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When hand sanding, do yourself a huge favor and sand just a few strokes at first and quickly check the result. This area of the panel looked pretty flat, but a few quick strokes with the sanding pad revealed some fine contouring that might otherwise have been missed. This then allows you to alter your approach if need be.
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Next we move onto DA sanding.
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Make sure you have the interface pad installed between the backing plate and the abrasive disc. This makes things far safer, and even allows you to work on contours with the palm sander.
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1500 grit on the DA palm sander and the finish is nice and uniform, if totally devoid of gloss.
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We follow with 3000 grit to refine the surface even more, and the gloss actually starts to come back. The folded arms are reflecting in the 3000 grit refined area, but his head disappears into the 1500 grit area. Imagine how much faster and easier it's going to be to buff out the already glossy 3000 grit section!
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Speaking of buffing out, we lay down a bead of M105 and get ready to compound. We'll eventually follow up with M205 on black or yellow foam, depending on how the finish is coming along.
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After a quick break for lunch, it's time for the guys to get to work.
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This is after hand sanding with 1200 grit, 2000 grit cross cut over the 1200, and finally 3000 grit cut in a third direction. Again, we can begin to see reflections in the surface following refinement with 3000 grit.
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All that white slurry you see is clear coat being leveled out.
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And here's what happens when you don't keep things really clean and flushed out. See those long straight lines that stand out from the background? Those are tracers; deeper cuts caused by a build up of paint residue and/or dislodged abrasive particles being trapped between the sandpaper and paint. These gouge into the paint, creating isolated deeper scratches that can be difficult to buff out.
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Dead center of this shot, cutting at a roughly 30 degree angle through the lights, is one of those tracers that still remains after compounding and polishing. The rest of the surface is darn near perfect, but this deep tracer really stands out.
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Here's another example of sanding marks that weren't quite removed in a multi step sanding process. You can see straight line scratches in multiple directions, meaning we've got marks from different grits, and that just shouldn't be. If the angled cuts are 2000 grit and the vertical cuts are 3000 grit, that tells us that not enough 3000 grit sanding was done to fully remove the previous 2000 grit marks. Compounding shouldn't have started yet since the 3000 grit step wasn't done fully. In fact, that we see two different grit marks here also tells us that compounding isn't finished..... don't even think about polishing yet!!

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After going back with 3000 grit finishing disc on a palm sander and then buffing out, this is the end result. Nice!!!
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With advancements in abrasives technology, DA polisher technology, microfiber pad technology and even compound technology, we can now routinely remove sanding marks with the MT300 very quickly.
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We'll close with a couple portraits of a job well done!!
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Selectchoice
Oct 19th, 2015, 07:06 PM
Looks like a great class with plenty of learning going on!