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Old 05-03-2005, 10:03 PM
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sanding curves

I have been through all the forums, but cant find the info i need. Im a self taught body worker, and im having problems sanding on a curved area. I have sanded every direction i can and i can get it straight one way but not the other. With my glove on it feels good and flat length ways, but it feels wavy the other way. Then if i get it feeling good that way, then its not the other way. Its getting on my nerves now. What am i doing wrong. I have flex sanders but that does not help. Is there a trick to sanding these curves.
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Old 05-03-2005, 11:57 PM
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For the most part X-ing strokes contour and back and forth strokes flaten. Also where you end a stroke ie. (stop) CHANGE DIRECTION of your sand strokes is just as important as their direction. This thread is going to get many replies as there are many seasoned body and paint people here with as many styles. There are some who no longer use filler at all. But the one thing we all use to check our progress is guide coats. Use guide coats on your filler often (alot,again and again) to help keep track of progress ..

Sanding is like mowing the grass.(grasshopper ) If you stop the mower in the same place to many times when you CHANGE DIRECTION the grass will be shorter in that spot than midway across the pass and fingers will point and people will tell...

I don't have a lawn cause of the parked cars but...
The same princible applies all the way through the steps of filing metal, sanding filler, primer, paint, clear to buffing . If the buffer's passes stop and CHANGE DIRECTION in the same place enough times it'll burn/cut through there for crying out loud. There are those who can take a perfectly painted new straight panel that was absolutly straight when it came out of the paint booh, and put waves in it by colorsanding and not thinking that WHERE they STOP AND CHANGE DIRECTION of the sanding stroke is IMPORTANT ...Same with spraying paint. but thats another story etc...

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Random orbital (dual action DA) sanders are the perfect example of the importance of random stop and direction changes of sand strokes for the same reason. . .


http://www.a2zautoforums.com/showpos...9&postcount=10

Last edited by milo; 05-05-2005 at 11:32 PM. Reason: spelling, twice
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Old 05-04-2005, 01:10 PM
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QUOTE: . There are those who can take a perfectly painted new straight panel that was abasolutly straight when it came out of the paint both, and put waves in it by colorsanding and not thinking that WHERE they STOP AND CHANGE DIRECTION of the sanding stroke is IMPORTANT ...Same with spraying paint. but thats another story etc...

I agree, I've seen people ruin the straightness of panels during the colorsanding and also when the paint was applied unevenly coat after coat. There really is alot of attention needed to make something considered
flawless.

Back to the original question, The flex sanders do help on these irregular shapes. Rounded fenders like those found on early to mid 40's vehicles can be a real challenge. What you need to do is blocksand the complete panel in an x pattern from front to back and reverse equally and never working one area more than another, you can cut till bare metal is showing then you'll need to decide if these spots are high and needs to be lowered or if the rest of the panel surface needs to be built up. Guide coat is a must and will show any low areas. Keeping your pattern as you work your way from front to back is key IMO. On really nice jobs I'll walk the whole side of the car blocking from one end to the other-but then panel alignment must be perfect.
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Old 05-04-2005, 04:56 PM
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sanding

Thanks you all, i dont care how long it takes me on the body, but it has to be straight. For someone like me that has to do all the work himself this site is the best. I did find out today that i was using my 40 grit to much and was taking off more than i put on. I dont want anything over 1/8 inch thick on the bondo, in fact im trying to keep it about 1/16 inch thick. And this means working the sheet metal more. Im sure ill have more questions to ask as i go along. I have a friend of mine that just got his 40 ford back today, but he has money and had it done by a restoration shop, in only 4 months. And it is very very nice. But i had to do this car on my own, and it will take me 3 or 4 years to do.To me if someone else does the work, then you cant brag to much. Anyway thanks for all your help.
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Old 05-04-2005, 08:03 PM
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Sanding blocks are SO important. I have so many that I keep laying around and someone comes in and pick's one up and starts nervous tapping on a table with it and I'm hollering at them and they are like "It's JUST a sanding block"
I can not count the number of people I've seen using their HAND'S to block out with. They usually have 3-4 FINGERS cutting 3-4 GROOVES into what they are trying to make straight. Even though the paper may be folder up,It's STILL not gona sand FLAT.
Sure hand sanding has a place but it's NOT in the middle of a panel.
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Old 05-07-2005, 07:38 PM
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Quote:
Originally Posted by baddbob

What you need to do is blocksand the complete panel in an x pattern from front to back and reverse equally and never working one area more than another, you can cut till bare metal is showing then you'll need to decide if these spots are high and needs to be lowered or if the rest of the panel surface needs to be built up. Guide coat is a must and will show any low areas. Keeping your pattern as you work your way from front to back is key IMO.
Baddbob,

Do you use guide coats only while wet sanding?
I have always dry sanded while straightening panels and have never used guide coats. It is easy for me to see the low spots that the board is not hitting. I can see that guide coats would be a must for wet sanding. But I am able to dry sand panels to perfection without guide coats.

Roger
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Old 05-07-2005, 09:36 PM
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I use a guidecoat for both dry and wetsanding. Some primers have a surface color or slight as sprayed shine that serves as a guidecoat visable when drysanding but I still prefer to guidecoat almost everything. Sometimes I will even guidecoat the final stages of filler work to be sure any coarse scratches are removed and to identify any pinholes, etc. Some jobs are more critical than others, when I did production work guidecoat wasn't always used.
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Old 05-07-2005, 11:13 PM
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While we're on the subject, not all paints make for a happy guide coat. If you don't need a guide coat that's cool but for the benifit of those new to the game...
A contrasting color spray can primer will sand best...
I've found that Sem's Trim Black works best for me. Even though the Sem company makes what they call "Guide Coat Black" in a spray can it seems the Trim Black is a better choice to have on hand since it'll do double duty and save picking up the wrong can when you really need Trim Black for something ,
These prices seem out of wack. They are priced the same at the autobody store in my town but the links show the two products
http://www.sjdiscounttools.com/sem38203.html
http://www.premiumautocare.com/semtrblpr.html

.
.The problem with "any old spray paint" is when they roll up and load up your sand papers before they can half start cutting..and this can cause cussing .
Some ole schoolers will remember using a rich oxy flame to soot the bondo...

Last edited by milo; 05-08-2005 at 01:03 AM. Reason: spelling way bad
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Old 05-08-2005, 07:56 AM
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I agree, don't use any enamel spraybomb products for the guidecoat. 3M makes a nice dry powder guidcoat that works really good, PPG and Transtar offer guidecoat in a spraybomb. Or you can do like I do, purchase some red or black economy laquer primer and use that. I buy an economy line gallon of the laquer primer and it lasts for a very long time, over reduce it some with laquer thinner and dust on a light fine coat- works great and only costs about $30 and lasts for a very very long time. You can keep some mixed in a sealed container ready for use.
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