EEVblog Electronics Community Forum
Electronics => Repair => Topic started by: Axtman on November 06, 2019, 06:26:50 am
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What products/procedures do you recommend to polish scratches out of clear plastic multimeter lenses? Thanks.
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This is an old trick: if the scratches are light, you can try with toothpaste.
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What products/procedures do you recommend to polish scratches out of clear plastic multimeter lenses? Thanks.
It's like polishing anything, start with a polishing medium suitable for the depth of scratches and then reduce the 'grit' of the polishing medium.
I used to use fine grit 'wet and dry' sandpaper with water under a tap then reduce to a fine brass polish called 'Brasso'.
With suitable effort you can remove the deepest of scratches and no one would know they were ever there.
I did this for many years when I worked in instrumentation.
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Ive used cutting compound and tcut with good rusults.
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I've used the kits for polishing scratches out of auto headlight lenses. No matter what method you use, if you can't take the lens out to polish it separately, mask off the area around the lens so you don't polish away lettering, etc. from the surrounding area. If you are trying to remove deep scratches using a drill with polishing pad, be careful not to use too much pressure/speed or you could heat the lens and make matters worse.
https://www.caroutfitter.com/best-headlight-restoration-kit-reviews/ (https://www.caroutfitter.com/best-headlight-restoration-kit-reviews/)
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I polish my meters' lenses with the plastic polisher called PlastX. I am sure there are bunch of plastic polishing products on Amazon or your local home improvement store. Why use toothpaste.
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Acetone removes the scratches... and more >:D
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In the US, the mostly widely available product line is Novus plastic polish: https://www.novuspolish.com/ (https://www.novuspolish.com/)
Toothpaste works well for soft plastic, but not polycarbonate.
As mentioned, deep scratches take a lot of patience to remove.
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This is an old trick: if the scratches are light, you can try with toothpaste.
I tried that and made it worse. Get proper polish.
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Try some acrylic polish that you can get from most craft shops or sellers of acrylic products. Brasso works well too.
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It depends on how deep your scratches are. I had to do my AN8008 which got a deep, large chemical fog. I was able to remove the lens, then used several grades of sandpaper starting with 600. Yes, this gets out the deep scratches, and makes the lens totally opaque, so then I used something like 1200, then 3000. Finally, I bought the Novus 3-pack of # 1, 2 and 3 plastic polishes. You work a while with the most aggressive paste, then the medium paste, and finally the final polishing liquid. It worked well, took a lot of time, and probably wasn't really worth it for a $20 meter, but it was educational.
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This is an old trick: if the scratches are light, you can try with toothpaste.
I tried that and made it worse. Get proper polish.
It does work. You have to go at it for a LONG time. Like an hour.
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It does work. You have to go at it for a LONG time. Like an hour.
That's the case with any polishing.It likely depends on what specific toothpaste you use but unless your unit is heavily scratched you're only going to make it worse. Polishing something smooth is a matter of progressively building up to finer polishing grits and toothpaste seems to be in the middle somewhere although you never know where. It may do in an emergency and when the result isn't vital but in all other cases it pays to just do it properly.
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As mentioned above.... Novus... Try a bottle of Novus #2.
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Been using Novus for several years.
Best system I have seen for polishing plastics (DMM displays for example) and much less aggressive than headlamp car products.
I use it a lot to polish scintillator plastics (for radiation detection) after machining on the lathe.
Start with the #3 "heavy scratch remover" if needed.
Go to #2 "fine scratch remover" and finish with "plastic clean and shine".
At that point I apply a drop of optical coupling gel to mate it to the photomultiplier surface.
Novus system works great as long as you do not apply too much force and are patient.
Also be careful not to mix the polishing tissues between the three grades and clean the surface properly between grades to avoid cross contamination of the polishing cloths.
If the surface has to be of optical quality avoid polishing only one portion as this will create a distortion (uncoated plastic glasses for example)
Also works great on scratched CDs.
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Whatever you end up using, keep in mind that you need to polish out a sufficiently large area around the scratch, too. Otherwise, with curved plastics, you'll likely create an optical distortion that might be more disturbing than the scratch itself.
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Start with the #3 "heavy scratch remover" if needed.
Go to #2 "fine scratch remover" and finish with "plastic clean and shine".
1200/1500 then 3000/3200+ grit wet sanding then going straight to #2 is generally more effective when necessary than trying to use the #3, although it can certainly be of some use in some circumstances. If done correctly with pressure applied over a large area, careful, proper wet sanding will generally provide better results than trying to hand polish with the #3, and the #1 is basically just a cleaner that you can replace with many other cleaner/waxer type products, depending on the end application..
You can certainly buy all three if you desire, but i think you'll find you use far more #2 than the others and will end up ordering a bigger bottle of it anyway if you start with one of the kits. :)
Seriously, just get yourself a bottle of #2 and you'll be likely be amazed at how well it works....
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+1 for NOVUS polish .... wonderful stuff.
Fraser
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I used this for the exact same purpose. It's excellent!
I can recommend it and I will defo use it again!
https://www.ebay.co.uk/itm/QUIXX-Xerapol-Acrylic-Plastic-Polish-Perspex-Scratch-Remover-Restoration-Kit-QA1/372303233091?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649 (https://www.ebay.co.uk/itm/QUIXX-Xerapol-Acrylic-Plastic-Polish-Perspex-Scratch-Remover-Restoration-Kit-QA1/372303233091?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649)
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Acetone removes the scratches... and more >:D
Yeah, like the entire polished finish of the plastic meter face.
I'm surprised you didn't recommend dynamite to remove small scratches from meter lenses.