Yeah, those are rather pricey. I found a 18" flexible sanding block with a spring steel base from, you guessed it, Harbor Freight. Works pretty damn good and it was cheap. I'm going to cut up some polycarb 1/8" sheet for some variable flex sanders and see how that goes. Thanks, Rat Bastad- a good one.
I always finish my plastic with 80 grit, feather the paint,then prime and guide coat. Block with 150 grit free cut paper, re-prime and then finish sand with 320 grit. This is the way I've been doing it for almost forty years, everyone learns a different way.
I took an auto body class at San Bernardino Community College thirty years ago that was taught by an instructor that had been doing body work since 1948. Lloyd Hammond was his name and he was the finest metal man I ever knew. He had a cross peen Proto body finishing hammer named “Ike“, the head was polished like a mirror so it would not leave scratches in the surface of the metal and it was on its third or fourth handle by then. When Lloyd was done metal finishing a panel all it needed was a light coat of lacquer primer, wet sand it with 600 grit and when it was painted it was straight like a mirror. Lloyd showed us how metal finishing was done. I was the best in the class at it and I sucked! After several weeks of welding, brazing, hammering, stretching, shrinking I finally realize my limits and eventually gave into the concept of using body filler. You can only grind and file on something for so long. I was taught by Lloyd if you were a sorry-ass-body-man (which I am) and you had to use body filler you should grind the metal so the grinder marks were lengthwise, in the direction you would normally being looking down the panel. Apply the schmooze (you could not call it Bondo in his class because that was a trade name) Sand the schmooze with 36 grit speed file paper in a crisscrossed pattern until you just see the metal starting to breakthrough around the edges of the dent or low spot, STOP sanding, do not try and make the schmooze smooth and pretty, all you will be doing at that point is creating a low spot. Just barely sand the schmooze with 80 grit paper to knock off the sharp edges from the 36 grit, your final sanding strokes should be lengthwise. If you have a hard line between the metal and the filler you have sanded too far and have created a low spot, you need another coat of schmooze. If the schmooze feathers out into the metal your probably still too low but your at the point where you can probably block it out with two, three or four... coats of primer. I don't want you to think were sculpting a car out of schmooze, if it’s more than a 1/16” thick you need to go back with your hammer and dolly and work on it some more. The trick is learning to know if it needs another coat of schmooze or of it will block out with the primer. Run the flat palm of your hand over the body work, if you can feel anything at all it probably needs another coat of schmooze. The waves that you are going to be blocking out with primer are ones that are too small to feel with your hand but big enough to see when they are painted. I agree with block sanding with fine paper, it will just ride up and down on the waves and the panel nevr seems to be getting any flatter, all your doing is wasting time and primer. I do all my blocking with 220 grit paper. Don’t let the paper get creases in it or build up on it. I sand with very light pressure until I hit metal then I give it another coat of primer and do it again. When I think I have it straight I give it another coat of primer and wet sand it with 400. Then I clean and dry the panel and take a paper towel and wipe it down with wax and grease remover. Before It evaporates it will look like the most beautiful glossy paint job you have ever seen. Look at it from all angles and if there is a wave in it you will see it. Then start cussing, go buy another gallon of primer and start the whole process all over again. It’s all about patience and how much primer you can afford. Jerry
A couple more tips that work for me. Block with a course paper, ( I use 100 grit), and as soon as you see the metal (or bog), starting to show STOP!! Any more blocking will just sand all the filler out from around the 'high" and make it worse. Allow enough primer still left there so you can smooth over with 180 grit. And the big tip.....As you will know, that once you have sanded through your guide coat you are sanding blind, having to remember where the guide coat had showed up the high and low spots. So, simply tint differently each primer coat so that you have a "continual guide coat". It will also show if you are sanding a "flat" onto a curved surface. I learnt this one trying to get the front of a set of 38 Ford guards (fenders) straight. It was like trying to block a ball!!
Here ya go buddy , I asked the same question a while back and someone posted this link. http://www.roddingroundtable.com/tech/articles/sanding1.html
Hello to all. Im currently working on my 1956 buick. Im block sanding the door off the car the only reason im doing so is because the door has a curve to it from front to back the car was sand blasted and epoxy primed. Should i be block sanding the car as a whole or in parts
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