Hand Sanding vs. Machine Sanding

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Countersteer46

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Can someone explain the difference between hand sanding and machine sanding? I've heard that you use machine sanding for coarser grits and hand sanding for finer grit. I've also been told the exact opposite, you hand sand with coarse grits and machine sand with finer grits.

Secondly, what's the difference between wet and dry sanding? I've been told wet sanding just makes your paper last longer.

Finally, if I want to take out orange peel, how high a grit do I finish with? I've been told anywhere from 2000 to 5000 and I'm frustrated with the inconsistent answers I'm getting.
 
Finally, if I want to take out orange peel, how high a grit do I finish with? I've been told anywhere from 2000 to 5000 and I'm frustrated with the inconsistent answers I'm getting.
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The higher grit you finish with, the easier it is to remove the sanding marks. Here's a thread from Mike Phillips that even includes a video:

Wow! 3M #5000 Grit Polishing I mean Sanding Discs!

Mike.Phillips@Autogeek said:
Video: Wow! 3M #5000 Grit Polishing I mean Sanding Discs!


Did some comparison testing between,

#1500 Grit Sanding Discs - Meguiar's
#1500 Foam Backed Finishing Discs - Meguiar's
#3000 Foam Backed Finishing Discs - Meguiar's
#5000 Foam Backed Finishing Discs - 3M
​
I'll let the pictures do the talking...

From left to right...

#1500 Grit Sanding Disc, #1500 Foam Backed Finishing Disc, #3000 Foam Backed Finishing Disc and #5000 Foam Backed Finishing Disc

50003M000.jpg
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It's been a while since I've posted anything. Last summer was just way too hot to do any cars and this spring has been really nice so, I've been buffing again.

I have a sanding question. I've been doing lots of headlight restorations with the Griot's 3" buffer and Unigrit sanding discs. My neighbors car got keyed on the passengers rear side. Pretty long scratches. I wonder if the Griot's 3" buffer and 3000 Unigrit discs would take those scratches out, or almost take them out. It's a black car and the scratches are white.

After sanding I would follow up with my 3401, Cyan pad and Black Fire SCR. Any advice on this would certainly be appreciated.
 
The GG3 with the 3000 discs would be a great place to start. Do you have the foam interface pad for use inbetween the bp and sanding disc.

Also do you have a PTG?
 
skipper1 said:
It's been a while since I've posted anything. Last summer was just way too hot to do any cars and this spring has been really nice so, I've been buffing again.

I have a sanding question. I've been doing lots of headlight restorations with the Griot's 3" buffer and Unigrit sanding discs. My neighbors car got keyed on the passengers rear side. Pretty long scratches. I wonder if the Griot's 3" buffer and 3000 Unigrit discs would take those scratches out, or almost take them out. It's a black car and the scratches are white.

After sanding I would follow up with my 3401, Cyan pad and Black Fire SCR. Any advice on this would certainly be appreciated.
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Can you feel the scratch with your finger nail? If so, you will need to use touch up paint as a filler.
 
Yep, got the foam interface. Sorry, I don't know what PTG is.

Can my fingernail grab the scratch? You bet, I don't think I can get the scratches completely out but I feel I can do some major damage to them.

OH, paint thickness guage. Yep, got one of those too.
 
skipper1 said:
Yep, got the foam interface. Sorry, I don't know what PTG is.

Can my fingernail grab the scratch? You bet, I don't think I can get the scratches completely out but I feel I can do some major damage to them.

OH, paint thickness guage. Yep, got one of those too.
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Sounds like your down to primer. Wet sanding without filling with paint won't help. Use your PTG first before wet sanding. Good Luck.:xyxthumbs:
 
Rsurfer said:
Sounds like your down to primer. Wet sanding without filling with paint won't help. Use your PTG first before wet sanding. Good Luck.:xyxthumbs:
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Would I want to get the matching paint, carefully fill in the scratches with a tooth pick and wait for it to dry or cure and then sand?
 
A lot of this will depend on the owner and if they want to follow through, which means they buy the paint. But, I sure will follow up.
 
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