When to sand using circular motions, and when in a single direction?

"Otto-the-Croatian-'Whoops my Volvo is a sedan'" (otto-the-croatian) 08/18/2018 at 13:25 • Filed to: diy, tips, help oppo, help, merci twingo

0

14

Just a quick question Oppo. I’m gonna refresh my hubcaps on the Twingo next week and paint them (Gold or black - thoughts?) and I’ve been checking out some tutorials. Sometimes I see people sanding in circular motions and sometimes in a single (or two-way) direction, like in the picture. Which one is correct for what application ?

Is it true that you sand circular when it’s plastic and one way when it’s metal or alumin(i)um? Or do you decide based on the context - if you’re applying primer on the surface later or not, etc.?

Thank you for the advice

- Sandy from Zagreb

...

Btw in the near future I’ll get rid of the hubcaps and paint the steelies a dark gold or copper or rose-gold kind of color. But until then I want to just do a quick temporary makeover.

Nom De Plume > Otto-the-Croatian-'Whoops my Volvo is a sedan' 08/18/2018 at 13:46

1

Why not plastidip?

Y ou use a circular sander on a wood floor and a belt sander building a piece of wooden furniture. These are both at least usually flat surfaces which I’m not sure your hubcaps are.

What I think will matter to you is how textured and flat the surface and hardness of finishing treatment are. Having no idea if they are plastic or aluminum it is hard to say if the third option, chemicals, would be viable.

I would think cleaning them enough to do a wrap or plastidip would be an easier short term solution but have no idea based on the information you provided.

Montalvo > Otto-the-Croatian-'Whoops my Volvo is a sedan' 08/18/2018 at 13:47

0

Im in no way knowledgeable or an expert but I’d probably stay away from circular motions. That way any imperfections that could occur are happening in one direction and can be “ masked” when looking from a different view. Anything involving swirls has a tendency to get noticed easier.

Otto-the-Croatian-'Whoops my Volvo is a sedan' > Montalvo 08/18/2018 at 13:57

0

Cool, thanks. I’ll keep that in mind.

I like cars: Jim Spanfeller is one ugly motherfucker > Otto-the-Croatian-'Whoops my Volvo is a sedan' 08/18/2018 at 13:57

3

With g rain if there’s a grain, otherwise go cir cles I think. I haven't sanded wood in a few years. 

Otto-the-Croatian-'Whoops my Volvo is a sedan' > Nom De Plume 08/18/2018 at 13:59

0

I agree that it would be but plastidip is more expensive and much harder to obtain in my area. It’s not common here yet. The local stores sell it at a ridiculously high price because it’s still a new technology, and ordering it online is also expensive ‘cause of the shipping costs.

The hubcaps are just plastic universal ones. For now just placeholders until I paint the steelies, so whatever I do to them d oesn’t matter, I’m free to experiment.

farscythe - makin da cawfee! > Otto-the-Croatian-'Whoops my Volvo is a sedan' 08/18/2018 at 14:06

0

plastic hubcaps?

coz if so id recommend fine scotchbrite

plastic grooves easy and all that jazz

also i know on aluminium its circular.. (plastic front fenders too.. but i know nothing of hubcaps other than use the finest sandingpaper/scotchbrite you can get or it will leave grooves)

Otto-the-Croatian-'Whoops my Volvo is a sedan' > farscythe - makin da cawfee! 08/18/2018 at 14:11

1

Plasic. And yeah, the grooves bit makes sense.

I’ve got up to about 2000 grit so I’ll be good I guess. I tried painting a nerf gun once and all I did was ruin the surface completely by using sandpaper. It just got more and more wrecked as I did it. It got kinda wooly, if that makes sense. Strands of plastic falling off and sticking up. But that was a different kind of  plastic to hubcaps.

MM54 > Otto-the-Croatian-'Whoops my Volvo is a sedan' 08/18/2018 at 14:16

1

Having spent the past two hours sanding trim, the back-and-forth is for wood (sanding with the grain) and either works for metal (though circular / random orbit is better). Plastic is soft so be very careful.

Nom De Plume > Otto-the-Croatian-'Whoops my Volvo is a sedan' 08/18/2018 at 14:20

0

Ah, experimenting is probably just what it will take. Since the finish is coming off one way or the other you can try a few methods. Heat might allow you to almost peel the finish off without warping or melting the plastic. Freezing would make the plastic too brittle.

I think the key is going to be removing as little plastic as possible using a variety of sanding and spot sanding techniques. A very lightly abrasive polishing pad at lower speeds on the end of a drill might do it. If not I’d aim for the lowest grit or lightest abrasive means at your disposal and work upwards until you are actually removing something. Instead of the typical 400 grit>>2000 grit to get a smooth finish.

farscythe - makin da cawfee! > Otto-the-Croatian-'Whoops my Volvo is a sedan' 08/18/2018 at 14:22

1

lol hubcaps will do more or less the same thing as the soaker if you go coarse enough tho

hand sanding i dont think you should go lower than 600 grit (tho.. i would give it a try with something much finer first and work your way down till you actually get a result that looks like sanding without too much effort)

Otto-the-Croatian-'Whoops my Volvo is a sedan' > farscythe - makin da cawfee! 08/18/2018 at 15:03

1

Going back down from fine to coarse. H aven’t thought of that.

Otto-the-Croatian-'Whoops my Volvo is a sedan' > Nom De Plume 08/18/2018 at 15:05

0

Thanks for the tip , I’ll try applying different temperatures as well. And going back from 2000 towards a more coarse paper seems to be a smart way to do it. Good. I’ll post on Oppo when I do it.

farscythe - makin da cawfee! > Otto-the-Croatian-'Whoops my Volvo is a sedan' 08/18/2018 at 15:14

0

lol normally that would be the wrong way round :)

Nom De Plume > Otto-the-Croatian-'Whoops my Volvo is a sedan' 08/18/2018 at 15:51

0

Sandpaper will create plenty of heat on its own. What I was suggesting was a plastic scraper after getting it good and warm. Alternately using a chemical, also sure to get plenty warm, and plastic scraper. If it peeled off and revealed the pristine surface below that would be more preferable than sanding.

Sanding should work fine as long as you are gentle. Expect to devise some way of burnishing the surface to get it smooth afterwards. If you Croats do any skiiing this final part of the process will be similar to prepping for wax. Again not sure what you have access to but a kitchen scrubbing pad like this is what we use in the states.