Different grits

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Different grits

Postby ken » March 21st, 2017, 11:35 am

I'm just starting out, and have a question about the various grits of sanding discs. The typical restoration uses 320, 600, and 1500 grits. Is there any guide as to when the 180, 500, 800 and 1200 grits would be used, or is it just trial and error?

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Re: Different grits

Postby Brent Deines » March 21st, 2017, 6:05 pm

I always use 320, 500, 800, 1200, 1500, 3000 (polishing disc). If the 320 is not cutting fast enough I drop to a 180 followed by the 320, 500, etc. In my opinion you will get way better results if you use a few more grits and keep them as close together as possible.

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Re: Different grits

Postby screenman » March 21st, 2017, 11:39 pm

I do not like to give Brent likes as he is way ahead of me in collecting them, as usual he is bang on correct. If you ask the manufacturers of the discs they will tell you this is how they should be used.

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Re: Different grits

Postby candyman » March 22nd, 2017, 11:13 am

:D
Brent Deines wrote:I always use 320, 500, 800, 1200, 1500, 3000 (polishing disc). If the 320 is not cutting fast enough I drop to a 180 followed by the 320, 500, etc. In my opinion you will get way better results if you use a few more grits and keep them as close together as possible.
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Re: Different grits

Postby ken » April 24th, 2017, 8:40 pm

Thanks Brent and screenman. I have another couple questions. I tried doing some headlights and some of the cloudiness didn't come off. I'm assuming then I should have dropped to the 180 grit and started again. This was the first time I used the kit. I also found the rotary sander slowed significantly with very little pressure. I found that frustrating. Is that part of the design? I checked the nut to make sure it wasn't loose...it was fine.

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Re: Different grits

Postby Brent Deines » April 25th, 2017, 9:40 am

It's possible the cloudiness didn't come out because you didn't use 180 but the only time I use that is if the OEM coating is very hard and not coming off with 320. I think you'll know when you get headlights with a really hard coating but you can check the thread here on the forum where people list cars they have found to be "harder than normal" to get an idea of some of the cars that technicians have had problems with.

Typically your last step, polishing with the 3000 polishing disc, is what takes away that last bit of cloudiness. It's extremely important to be patient with this step and even use an extra disc if you are not getting the desired results, although I don't typically find that necessary.

I like to go one step further and polish the headlights with Delta Kits Premium Polishing Compound, part number 54315 , and a rotary polisher such as the Makita model that we use in our shop, right before I apply Infinity 4.1. Most of our customers don't find this additional step necessary but it does take your end results to the next level. This is very important when only restoring a headlight on one side to match the look of a new one on the other side.

Yes, the Griots random orbital tool is designed to slow or even stop rotating if too much pressure is applied. This significantly minimizes swirl marks and prevents gouging. If you find the sanding process is taking too long you may need to use a courser disc but you should not increase the pressure. Just the pressure of the tool on the surface of the lens is all you need for superior results. Some technicians prefer a rotary sander or polisher such as the Makita mentioned above but most, myself included, find them too difficult to control and end up damaging the lens and/or surrounding surfaces when used for sanding. We've done extensive testing of dozens of different tools for sanding headlights and if used correctly the Griots tool is the best we've found to date for sanding.

Again, not everyone will agree with me on this but I have quite a selection of various electric and air tools that I have tried but the Griots random orbit is my favorite for sanding and the Makita is my favorite for polishing with a liquid polish.

Every step of the sanding process is important for the best possible results so it’s important not to skip steps or to rush steps until you are getting the desired results. Once you are achieving great results consistently you can start experimenting but I follow the exact same procedure every time with the exception of sometimes starting with 320 and for really tough coatings starting with 180.

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Re: Different grits

Postby ken » April 26th, 2017, 11:46 am

Thanks Brent. Good to know.

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Re: Different grits

Postby Brent Deines » April 26th, 2017, 2:14 pm

You're welcome Ken. If you are having problems please don't hesitate to call our office. Usually if we walk through the process with you start to finish we can help identify some minor detail that could be the cause.

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Re: Different grits

Postby screenman » April 26th, 2017, 10:07 pm

To add to Brents excellent advice, I have on a few occasions come across lights where there is cloudiness is inside the light caused I feel be people using the wrong bulb.

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Re: Different grits

Postby Brent Deines » April 27th, 2017, 7:53 am

That's a great point Graham. We've seen people use really hot bulbs that cause problems on the inside and if there is a crack in the front or back of the light they can get filled with dirt, etc. I was focusing on the exterior restoration process but completely ignored the fact that there are other reasons a lens may not clear up 100% that have nothing to do with that process.

I really hate to do it for fear that you will get more thumbs up than me but I'm going to have to give you one this time around. Thanks! :D


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