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Old 10-22-2005, 06:16 PM
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DA scratches when color sanding

Can someone tell me why when you color sand with a DA 1000, then 1500 then 2000 grit and buff you can see little swirly Q scratches still under there, not buffing out.Matthew is buffing right now and having to resand every panel by hand to get them out. Is there a reason they are not coming out from the DA itself?? Seems like much more work to me?? He ask me to come and post a thread to see if someone would know for sure.He already spoke to someone about it this morning and tried slowing his sanding speed way down, but still the scratches are showing up.He also made sure his pad was kept clean and not clogged. Matthew also said this is the newer way shops are sanding now days, so he knows there has to be something he is doing wrong to get those scratches.Anyone?

Amanda
BondoKing's Wife

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Old 10-22-2005, 06:26 PM
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they're called pig tails. the paint builds a small speck on the paper and mars the surface. change paper more often and dont let the da stop spinning. iif it stops it heats up and sticks the residue in a ball. i no longer use a da because of them. too hard to get rid of. i use an orbital block.
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Old 10-22-2005, 07:09 PM
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yes this is true. when i do a car a always use a da and the pigtails are from one of 2 things. one is what was stated above and two is plain and simple dirt under the pad. one little speck of something and its all over so it must be clean where you are doing it. one thing i noticed helps is make sure you put a soft interface pad on the da. this made a hugh difference. my normal procedure for wetsanding is a da with a psa pad and 800. i wetsand with that to start then clean off and dry the panel then switch to a hookit pad w/soft interface and the 3m 1200 dry discs. you can goto the 1500 if you want but its really not necessary. those dry discs are a key too. i had some 3m wet/dry 2000 hookit disks....no good. they leave pigtails all over the place. normally i would goto 2000 wet by hand but that 1200 dry leaves almost as fine a finish as 2000. this procedure gives me a really flat finish in record time. fastest way i've ever found. on an average i might get anywhere from 1 to 6 pigtails on a whole car that when i'm done i just go back with a little 2000 wet by hand a get them out.
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Old 10-23-2005, 08:51 AM
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Cleaning the PSA pad between paper changes is a good habit as you can get "stuff" between without even knowing it. That IS glue on there ya know.
The interface pad's are a great addition to the arsenol but anytime your dry sanding,you can get tail's.Just part of the game.
A gray scotch pad wipe of the paper will clean those specks of build off nicely if you start getting the pig tails.

He could also be getting debris blown on to the car as well if your working outside or got a fan blowing on the vehicle in the shop.

We talked awhile back about a dedicated DA for color sanding as "stuff" from your body work DA can contaminate (fall out of) it on to the surface causing a world of trouble.

And, Of course,The clear not being dry enough can cause problem's as well.

So, Do WE get cake too for helping YOU out???

Mike.
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Old 10-23-2005, 01:52 PM
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Call me a dinosaur, but to me there's just nothing better than a trained hand and a clean water supply to ensure excellent color sanding. I just won't use the DA unless it's going to be repainted!
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Old 10-23-2005, 07:27 PM
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I totally agree with crashtech. Color sand by hand ONLY. More control less re doing what you mess up with the machine.
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Old 10-24-2005, 07:00 AM
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I have never used a DA for color sanding and was thinking of trying it,
But now I don't know if I should.
I have one of those air "jitterbug" type sanders that I never used.
Would that be better?
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Old 10-24-2005, 07:13 AM
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I agree, using a DA for color sanding? I would not even think of it. Prep work and the price of materials now a days, why try and save a little time using a DA for color sanding...doesn't make sense to me...I guess I am also a dinosaur. Hand color sanding is the only way for me. As mentioned above, one tiny spec of debris and the DA has it all over the place before you realize it.
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Old 10-24-2005, 07:31 AM
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eastwood sells a small gitter bug with a water hose on it. it is excellent for blocking but it too can leave pigtails although the flushing of the water reduces it a lot. your still going to have to hand jive it some but this block can save some pain on old joints
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Old 10-24-2005, 07:37 AM
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What about the Abralon 4000 grit padded back DA paper?
I have read a few posts earlier that this works really well.
Are there any pig tail problems with this stuff?
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Old 10-24-2005, 08:41 AM
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Quote:
Originally Posted by roger1
What about the Abralon 4000 grit padded back DA paper?
If you're talking about the foam discs, And I think you are, I love them
but only after initially hand cutting with a coarser grit.
They didn't do much by themselves.
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Old 10-24-2005, 08:48 AM
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Yes, I am talking about the foam discs.

I was going to give them a try for the first time on my present project.
And, was intending to hand sand with coarser paper first as you say.

My project is ss urethane. What would you suggest starting out with?
I was thinking 1000 or 1200 then 2000 by hand and then go to the Abralon foam discs with the DA. Still may be a little scary to use a DA for me. I have this fear that I'll sand the paint too thin.

Also, have you had that pig tail problem with the foam discs?

Roger
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Old 10-24-2005, 09:16 AM
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I haven't had the pigtails with the foam discs.
I have gotten away with hand cutting first with 1000 grit
(and a lot of water) and using the foam 4000 grit, also
with a lot of water and the result was a nice semi-gloss shine
that a foam pad on my buffer brings out a great finish with
only medium cut polishing compound.
I've eliminated the wool pad and coarse compound first step,
which always gave me a few scratches.
I found the 2000 grit foam pads still need the coarse compound
first but a foam buffing pad took them out easily before the polishing step.
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Old 10-24-2005, 11:06 AM
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Here is the gig with the DA sanding.. Always I have done it by hand, and recently thought that maybe I was becoming a dinasouar myself with perhaps my antiquated ways, so I buy a new da just for color sanding and the foam backing pads ( I bought mirka and 3m... 3m is much better btw)... I thought faster was better when running the da... I also decided on using water instead of dry to keep the paper from loading....It works, but if you have allot of dirt and specs in the topcoat, which I did, you best cut that by hand then get out your da... There is no way you will keep all that from getting under the paper... If it is a spec here and there that is one thing....

IMO if you use 1000 grit you still need to use 2000 before going to 4000 Abralon Mirka disc... I dont think there is anyway that the 4000 pad is going to remove 1000 grit scratches as suggested above... Try it on a black car... wont work!!!

For me this has been a tough learning experience ( as always), but I will keep messing with it until I get it right..

I think the 3m hookit system that Mrclean says makes all the difference will be what I use next... I got about 100 dollars worth of Mirka DA paper I bought just for color sanding... Can u say ebay blue light special..

If my wife had never posted this for me, I would have never tried it again, but now through this thread allot of information has been laid out to see where i need to make changes..

Thanks guys for your help

Matthew
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Old 10-24-2005, 12:26 PM
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Quote:
Originally Posted by BondoKing
IMO if you use 1000 grit you still need to use 2000 before going to 4000 Abralon Mirka disc... I dont think there is anyway that the 4000 pad is going to remove 1000 grit scratches as suggested above... Try it on a black car... wont work!!!
Oh it will work, it's just a matter of how long it takes for it to work.
I can go through the clear and the color to the primer with a 4000 grit,
It's just a matter of how long it will take, or how long you're willing
to hold the DA there. Remember, it cuts a whole lot faster on a DA
than doing it by hand.
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