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TOPIC: color sanding - how long to sand with each grit? Also, foam pad effect?

color sanding - how long to sand with each grit? Also, foam pad effect? 06 Jun 2020 17:13 #827485

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Oh man, I am so close to a really nice finished paint project. I got through my first attempt at cutting and buffing the clear coat (2 coats of SprayMax 2K Clear Gloss) but I'm still noticing some fine scratches. In trying to figure out where I might have gone wrong, I realized I might not have been partitioning my time wisely between the various grits. I probably spent the most time sanding with 1000 grit, then quite a bit less with 1500, 2000, 2500 and 3000 grits. Maybe those ratios should be reversed, like I should be spending the most time sanding with the finer grits to help polish out the coarse grit scratches? Does anybody have advice for me in that regard?

I'm thinking another cause may be the density of the foam pad I was using for cutting, but I don't know if a pad can really make that much of a difference. I did notice that my front fender, which I cut with the stiffest of three foam pads, didn't have the same scratches I'm seeing elsewhere. For the rest of the body parts I used the middle firmness pad of the three.
1990 Zephyr zr550 B1
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color sanding - how long to sand with each grit? Also, foam pad effect? 06 Jun 2020 18:06 #827497

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I have used 600, 1000, 2000, 3000, then polishing compound with a rag.
It you want to experiment use different grits on different sections then look at the part on an angle in the sun.

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color sanding - how long to sand with each grit? Also, foam pad effect? 07 Jun 2020 02:02 #827507

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cleaning really well between grits is critical. I would buff with a large wool pad, a buffer capable of 15000 RPM, and coarse buffing compound, then move to foam and finishing compound. If you do this there really is not much need to go past 1500 grit on the wet sand.
-Vic
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Last edit: by DoctoRot.

color sanding - how long to sand with each grit? Also, foam pad effect? 07 Jun 2020 13:20 #827535

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15,000 RPM???
Uhhhhhh...too high
Maybe 1500rpm with a rotary buffer.

In the video included they use a Rupes 21 running 3500rpm...and that's a random orbital.
www.rupes.com/product/lhr21iii/

You will burn through the paint if you use too high of a speed.

81-KZ440-D2. Louis Dudzik's GM HEI ignition module converted 2015--no issues, Motogadget m-unit blue.

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color sanding - how long to sand with each grit? Also, foam pad effect? 07 Jun 2020 18:46 #827554

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You're going to cut through the clear if you do much sanding. 2 coats of spraymax ain't much.
The following user(s) said Thank You: z1kzonly

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color sanding - how long to sand with each grit? Also, foam pad effect? 11 Jun 2020 06:40 #827856

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Like Dr Rot said, the cutting compound takes it to a point where only fine swirls are visible only when viewed from the right angle in the right light. To get rid of the swirls you need a practically sterile soft cotton rag with fine buffing compound. At that point I finish it off by hand and cleanliness is utmost importance. Drop a rag, it's done, and the surface you set your rags on should also be dust/dirt free. When painting a tank and side covers I'll go through 2 full cans of Spraymax. That's enough for at least 4 coats which lets you do most of the work with 600 without fear of cutting through, of course while being very careful around the edges. I'd definitely throw down another can rather than risk going through. This guy on Ebay has the best price for Spraymax I've found. 14 bucks is a cheap insurance policy.

KZ900

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color sanding - how long to sand with each grit? Also, foam pad effect? 11 Jun 2020 06:45 #827857

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F64 wrote: 15,000 RPM???
Uhhhhhh...too high
Maybe 1500rpm with a rotary buffer.

In the video included they use a Rupes 21 running 3500rpm...and that's a random orbital.
www.rupes.com/product/lhr21iii/

You will burn through the paint if you use too high of a speed.


I love this guy's videos. I've learned a lot from him.
KZ900
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color sanding - how long to sand with each grit? Also, foam pad effect? 11 Jun 2020 13:23 #827919

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Robb,
The paint you listed is a 1K not a 2K.
The 1K won't be as resistant to chemical attack as the 2K.
81-KZ440-D2. Louis Dudzik's GM HEI ignition module converted 2015--no issues, Motogadget m-unit blue.

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color sanding - how long to sand with each grit? Also, foam pad effect? 11 Jun 2020 16:48 #827937

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Yes, minimum 1500 not 15000 - typo
Rotary buffer, your shoulder and elbow with thank you. they are pretty cheap at harbor freight. stay away from the edges its easy to burn through.

Start buffing with a wool pad and a coarse compound then move to medium foam with fine compound and finish with fine foam and fine compound. I use 3M products. You can get a mirror finish that is not easily replicable by hand because of the friction generated by the buffer.
-Vic
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'78 kz1000 LTD long term project

'80 kz750G project

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Last edit: by DoctoRot.

color sanding - how long to sand with each grit? Also, foam pad effect? 12 Jun 2020 06:48 #827977

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Sorry I missed that. The best deal though is on Ebay. I've been getting it for 17 to 18 bucks there no tax. Was paying 22 at Sherwin Williams Auto Paint store.
KZ900

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color sanding - how long to sand with each grit? Also, foam pad effect? 12 Jun 2020 09:42 #827994

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Nessism wrote: You're going to cut through the clear if you do much sanding. 2 coats of spraymax ain't much.


Nothing worse, in the gut feeling as the wheel rubs through the clear into the paint, as your watching, pulling up the buffer.! On an edge or where ever.
Few years back, painted a 74 Z1A , Chrysler Daytona Blue. Buffed through a small spot on tail piece, had my pinstripe guy paint a small spider over the mark.
Livin in "CheektaVegas, NY
Still have a Kaw! 76 KZ900 Pro-Street.
Went thru 25 of these in 40 yrs.

And The Old Girl, Harley 75 FLH Electra Glide,
Old faithful! Points ign. Bendix Orig. carb.
Starts everytime!

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