Random orbit sander for clear vs wet sanding?

C

C10chas

I have a 6" sander with 3/32" orbit and a 3m hook & loop interface pad, how well would this work cutting clear (open areas, not edges/corner/radius) for the first cut with say 600-800 before switching to wet 1000-1500?
Lets hear the pros and cons!
 
not for blocking. da starts at 1000 and even then you best have control and know how much you are cutting it.
 
It can be done, you just need to watch what your doing.. Experience comes into play here, however that experience comes at a price. Its easy to burn thru not paying attention very easy!.. I have DA'd many cars with P400 without the interface pad on all flat surfaces.. ie.. the hood, roof, decklid, etc.. Then hand sand everything else.. You could use an interface pad for the contoured panels, but they wont be straight like they should vs using the block on those spots..

Like I said experience really makes a difference here.. I dont mind at all to take a machine to clear or any substrate.. BUT I have tore up a bunch of paint along the way and had to fix it.. That was my price for learning, but to me it was worth it..

I also think like this.. Your gonna reclear anyway, so if you burn thru somewhere as long as its not a candy job here, no big deal, just simply feather some base over those spots before you shoot the flow coat.
 
I do use a soft block, but the block still does a better job and is much firmer than an interface pad on a DA bro... There is a large difference between the two
 
Bondoking;1274 said:
I do use a soft block, but the block still does a better job and is much firmer than an interface pad on a DA bro... There is a large difference between the two
Click to expand...

BK, agreed, the interface is very soft, I was referring to the block used when wet sanding, not a rigid block right?
 
I havent used wet sandpaper in years. Been doing all my colorsanding with a da for as long as i can remember. These guys are right though, you need good control and feel with a da. In most cases i start with 1000 finishing film, then 1500 and then switch to 3000 trizact discs.
 
I've been undecided on the da's myself, when i use one i do 800, then 1200 then 3000.
The reason I am unsure is that it seems like you have so much more urethane peel left when using a DA, versus when you use a block.
 
Chad.S;1419 said:
I've been undecided on the da's myself, when i use one i do 800, then 1200 then 3000.
The reason I am unsure is that it seems like you have so much more urethane peel left when using a DA, versus when you use a block.
Click to expand...

Exactly, To get it straight and flat there's only one way for me-by hand with blocking.
 
I agree with you guys. If you start at 6 or 800 it will take out maybe half of it but thats it. i dont get much of that problem though because i clear twice and on my second round use a thinner clear and i am carefull not to spray heavy to create the wave. Half the battle is to not spray it with wave. Of coure thats easier said than done.
 
i use a 9 in hard block with 600 after first clear. after second clear i switch to the da with a soft pad. jim got me to dry sanding it . only complaint is the dust . one advantage to the dry sanding is you can see any imperfections pretty easy . learning to shoot paint is not all that hard but the art of polishing takes a lot of laps . i still use blue tape . i absolutely hate a repair.
 
How do you all deal with concave (reverse) curves? A common example being '73-'87 Chevy pickups, that have a major reverse running the length of the truck above the body line. I can usually see imperfections in these areas under fluorescent light, even after buffing. I feel this has gotten worse for me as solids in the clear have gone up. I am ready to switch to fat fender cars with no reverses if I can't figure out how to get them to appear perfectly straight!
 
Maybe no one else sees what I see, or I am having a problem specific to my technique.

Looking at these reversed areas lengthwise, they look perfect. It's only when standing perpendicular to the panel, and catching a reflection from inside the reverse, can the imperfections be seen.

I would love to hear how the pros deal with areas where flat blocks can't go, I would share my methods if they were proving 100% successful, but they are not.

P.S. Apparently, the average person can't see what I'm talking about, or if they do, they are too polite to comment upon it.
 
I know exactly what you're seeing there, crash, but I can't explain it. Did a '34 Chevy street rod and all was just great EXCEPT for the rear panel below the trunk lid where it curves out to the rear bumper (concave). Tried every trick I knew to make it look 'right' but never was satisfied with it. Of course the customer never seen it or even understood what I was trying to show him (not a good business practice, by the way!). It was only noticeable under the flouresent lights at the right angle, but outside in the sun you would never see it. I. too, would love to hear some methods to help 'correst this dilemma.
 
It's good to know I'm not alone! The worst panel I have done was a rear gate on an '85 Blazer that I painted a black cherry color. Not only did the gate have the same typical shape as the side, there is also a large reinforcing rib near the top of the panel that stops smooth sanding action. I never got happy with that gate, even after wetsanding it and re-clearing it.

But, the customer is thrilled with the thing, it's probably the nicest '85 Blazer I've ever seen, even with the stuff that drives me crazy...
 
Jim C;1278 said:
I havent used wet sandpaper in years. Been doing all my colorsanding with a da for as long as i can remember. These guys are right though, you need good control and feel with a da. In most cases i start with 1000 finishing film, then 1500 and then switch to 3000 trizact discs.
Click to expand...

Do you "wet sand" with the DA? In auto body class I would dry sand with the DA using 1000,1500 and 2000 finishing films, but then my teacher got upset at me and told me me that I needed to use water/soap, because otherwise I'd clog up and kill the pads fast. I've never been confident that he was right, although I agree that the pads clog up faster sanding dry.
 
OK, first, the original question was about a "RO" (random orbit)
not a "DA" (dual action) BIG DIFFERENCE!!!!!
Most air sanders are DA's, which spin fast (RPM)
and oscilate slow (orbits)
Most RO sanders are electric,
they spin much slower and orbit much faster.
Both sanders come in mostly 3 different orbit sizes
usually from 3/16" to 3/32"
All these combinations makes a big difference in how they sand.
A DA will be more aggressive than a RO.
I find a RO with a small orbit and slowed to it's minimum speed (RPM)
will sand clear longer before loading the paper.
The faster spinning DA's tend to heat it more and clog.
Even slowing them down, which helps, doesn't go as far as my RO.
Electric RO sanders come in two types too.
The palm sander type is for fine finishing and mostly for woodworkers,
but the "right angle" RO's are made to be more aggressive by putting out
higher RPM's and work good for clearcoat sanding and fine polishing.
this all gets confusing but the specs for RO's are on the nameplate
and usually list "OPM"s (orbits per minute) so you can compare.
I like the Porter Cable "right angle" RO for clear sanding.
It's the same tool for sanding or polishing.
http://www.deltaportercable.com/Products/CategoryOverview.aspx?catPath=4272.4288.4291
Here's the "palm sander" RO which I only use for wood, it's just to
slow for automotive.
http://www.deltaportercable.com/Products/CategoryOverview.aspx?catPath=4272.4288.4290
 
crashtech;1519 said:
How do you all deal with concave (reverse) curves?
Click to expand...

You don't have to use a hard block on clear to get a straight finish,
if you sand with coarse paper, like 400 grit.
Anything above 600 will basically not straighten but only smooth.
So a soft block with 400 on those curves will get it straight if you
sand it properly, then the finer grits won't change it.
You have to be careful how you sand, not little overlapping strokes
but long strokes to cancel out each other otherwise you'll
create waves that appear like lines from bad bodywork.
I hope that makes sense. It's hard to explain without showing.
 
You must log in or register to reply here.
Back
Top