Random orbit vs. orbital vs inline sander

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PostPosted: Sat Jul 10, 2021 12:51 pm
Hello all first time poster. I am currently starting to use 2x urethane primer,base, clear on high gloss cabinet projects. I am looking at sanders for sanding flat panels of various sizes some are smaller like 6" x 18" to large panels 18" x 90+".

Im just not sure which would be my best bet for getting nice flat finish. I have run into issues before with RO scratches showing up so I was wondering if just a orbital style would offer better finsh or inline. Im planning on sanding primer to 400 prior to base coat. Whatever sander I get I would like good dust collection. I currently have a festool ets 125 req 5" RO with 2mm orbit and a pneumatic sander I got also 5" with short throw. Im looking at the following sanders. Main use is prepping the primer prior to base and knocking down the orange peel in the clear prior to polish. I used the pneumatic DA before and noticed I had a much more difficult time getting out the swirls than I did if I hand sanded inline even with a coarser paper. So Im leaning toward the Dynaline but the price is up there I like the 3m orbital but worried I might still have swirl issues the Big electric would be for primer prep only on BIG panels. Any advise is appreciated even though it not "automotive" it is automotive finishes so figured I would ask here. thanks

https://www.amazon.com/Bosch-OS50VC-120-Volt-Finishing-Vibration/dp/B00B7EU1I4/ref=sr_1_24?dchild=1&keywords=bosch+sander&qid=1625938944&s=industrial&sr=1-24

https://www.amazon.com/3M-Orbital-Sander-Air-Powered-Central/dp/B007UUFV8Y/ref=pd_sbs_4/132-4190315-5044653?pd_rd_w=r0wty&pf_rd_p=f8e24c42-8be0-4374-84aa-bb08fd897453&pf_rd_r=VWTCDN4SFATCRYZ7KP43&pd_rd_r=1c8a8138-68e0-42d1-8ac5-7138bfaff55f&pd_rd_wg=j3I7n&pd_rd_i=B007UUFV8Y&psc=1

https://www.amazon.com/Dynabrade-57404-Dynaline-Central-Vacuum-3/dp/B00KF9OJQM

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PostPosted: Sat Jul 10, 2021 2:41 pm
I think your problem is more likely to be the paper grit size than the tool.

Also, RO machines have to be moved slowly, like their directions say,
most people go back and forth way to fast and that is the leading
problem of getting scratches and swirls.

If you really want to sand primer smooth and straight, nothing
beats hand sanding with a block. And it really doesn't take that much more time.
(just a couple of thoughts I hope can help)
JC.

(It's not custom painting-it's custom sanding)



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PostPosted: Sat Jul 10, 2021 3:19 pm
Thanks for the response, my biggest issue with hand sanding is dust control. Right now my 2 car garage is my everything everything space. cnc space, assembly, sanding and finishing. Space is tight. I actually dont mind hand sanding but the dust is much worse. With a power sander I can hook up my dust extractor and catch 90+% at the source. The primer I use turns to baby powder so it sands very easy but it makes a pretty good mess too plus the paper stays cleaner. I thought about getting a sanding block that hooks to the dust extractor. Hand sanding is one thing but hand sanding with a hose attached doesnt thrill me. With a power sander I dont mind the hose as much. One hand on the sander just guiding it along and one holding the hose so it doesnt mar the surface is much better than dragging the hose back and forth.

Im kind of leaning towards that 3m sander it looks like it would check a lot of the boxes without getting me in trouble with the CFO. It looks small enough to handle the smaller panels but large enough for the bigger panels with a certain level of blocking ability to keep everything nice and flat with the added benefit of some having some dust control, and not real aggressive. I really need a "fine" finishing sander I almost feel the DA is to much. Plus the 3m would probably work for wet sanding too provided I can find wet paper for it (I havent checked on that yet). I have to be careful if wet sanding as most panels are MDF so water will be used sparingly. I just have never used one so its hard to drop 350 bucks. $400 with paper without knowing its going to give better results.

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PostPosted: Sun Jul 11, 2021 8:44 am
For electric machine sanding I like the Porter Cable "right angle"
sander polisher. Shop around for a better price.

https://www.amazon.com/PORTER-CABLE-Ran ... =hi&sr=1-2

The right angle type random orbital (electric) sanders are more aggressive than the
typical woodworking type palm sanders and they are less aggressive than a air DA type.
I find this Porter Cable one a good balance for finish work, I use it a lot to sand clearcoat
before buffing.
It can be fitted with a dust collection system and can use 5" or 6" discs.
They sell different counterweights for the different disk sizes but I use the
same one for all and it does fine.
I've used this tool a lot over the last 15 yrs and it has held up well.
I like the Velcro type disk paper attachment.
I've also used it a lot in my wood shop for cabinet sanding, have not ever tried
it for polishing, usually use my buffer instead.
JC.

(It's not custom painting-it's custom sanding)



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PostPosted: Sun Jul 11, 2021 10:34 am
I find scratches become an issue mostly with clogged paper.
Checking and changing or cleaning the disk helps

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PostPosted: Sun Jul 11, 2021 5:34 pm
RamblerRacer wrote:I find scratches become an issue mostly with clogged paper.
Checking and changing or cleaning the disk helps


if your paper is clogging there is other issues, like primer not curing
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PostPosted: Mon Jul 12, 2021 5:13 am
Thanks everyone, The issue I had with the RO sanding the clear was odd. I used a 5" 3/32 stroke RO sander with a soft interface pad. I used plenty of water and dont feel I moved real fast but will slow it down even more in the future. The problem seemed to be no matter what I did I always had some slight swirl/scratches marks left by the sander even at 3000 grit and higher. Granted they where hard to see but they were there. It was cheaper paper and didnt try any 3m Trizact but I had better results sanding by hand (inline) even using 2000g than I did with 3000 on the RO. I ended up doing it in two stages using the RO to level out and remove any orange peel and then go back over by hand before polishing. I was using a foam pad polisher on a DA style right angle (harbor freight) polisher. So it wasn't as aggressive as a wool pad on a rotary. If my memory serves me correctly I used 1000 grit on the RO and then 1500 and 2000 by hand then used 3m finesse it. It could have been a grit progression problem as well. Perhaps I wasn't getting all the scratches out from the previous step but all I know is it seemed the hand (inline) sanding gave way better results no matter what the grit.

I was experimenting a bit so, when sanding clear with either a orbital or RO sander what grit would you start with and the steps in grit assuming it was a good clear coat job (no runs or "heavy" orange peel say just slightly worse than a factory style paint job

I am also planning on getting the newer dewalt cordless RO polisher with a 5mm stroke to replace the HF unit. My hope is the 5mm orbit will be a little more aggressive without being too aggressive and loosing the cord which I hate.

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PostPosted: Mon Jul 12, 2021 8:31 am
A high quality paper will make a big difference.
I like the 3M purple for sanding clear.
I usually start with 1500 disks then 2000, sometimes
I will follow with a 3000 grit Mirka Abralon disc, but
buffing after 2000 grit is mostly what I do.
I sand it all dry.

Letting your primer cure an extra day or two may also help
with swirls when they're caused by paint buildup on the disk.
Sometimes the paint is just to soft.
JC.

(It's not custom painting-it's custom sanding)



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PostPosted: Mon Jul 12, 2021 9:29 am
Thanks, Im familiar with the 3m purple discs as being cubitron and I to love that stuff. Its my go to from now on. I just went through trying a bunch of different brands and the 3m cubitron was by far the the best I found. However, I was under the impression that 400g or 600 was the max for the cubitron. Im going to check the 3m website and look better. Im going to have to try their Trizact which is what I thought was 3m's clear sanding system. its a finer grit discs and they have a thin foam backer. Either way I will try better sand paper for sanding the clear. I will also try waiting longer to sand the primer next time. I did sand it the same day it seemed dry it but was clogging all the papers except for the cubitron but 220 was my finest grit I had on hand for the cubitron so I had to finish with some other (Dura gold) 400g. It wasnt gumming up on the disc but I had to keep blowing it off even with the dust extractor hooked up.

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PostPosted: Mon Jul 12, 2021 3:47 pm
2K urethane primers shrink a lot in 24 hrs, I won't paint
over it if it's less than 48 hrs old.
It holds out way better waiting a little longer.
If doing a show car finish, I'll wait 4 to 5 days minimum.
JC.

(It's not custom painting-it's custom sanding)
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