Paint Thickness Gauge, Cheapo Harbor Freight First Test Results.

oldmodman

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Cliff notes.

It's worth the money and works great for way less money.

I ordered it online since it was not carried in my local Harbor Freight store. It arrived in about a week.

It looks like a generic remote reading temp gauge, with different setting buttons.

It has a trigger for on-off and take a reading.

On the side it has a backlight button, cal (or calibrate) button. Up and down buttons for changing the calibration. And a button to toggle between inch and metric. The inch readings are in thousands of an inch and tenths of a thousandth. The metric is in microns and if much more useful since it reads in thousandths of a millimeter, a much smaller measurement.

Before using the gauge you must calibrate it. You take a reading of a round metal disc that is provided with the gauge, then zero the gauge with the up and down buttons. Then you take another reading of the metal plate but with the test strip between the gauge and the plate. And you use the up and down buttons to make the meter read exactly what is printed on the test strip. Then you are ready to use the gauge.

The first car I tested it on was my 1992 Ford Explorer. I got reading of 112 microns on the hood, 83 on the roof, and 221 on the new paint on the repaired drivers door. I know that the door was re-skinned so I know that it has only new paint on it. Just goes to show you how thin the paint build is on factory paint. I tested several other cars with similar results.

Now for the interesting part.

I got out my test hood, sandpaper, spray bottle of water, rubber sanding blocks, Makita rotary, heavy wool pad, and Meguiars #84 cutting compound and went to work.

I started by taking ten measurements at various places on the hood. I got readings that were very consistent. 127 down to 114 microns.

After sanding for appx one hundred strokes, back and forth with 1500 grit paper and water. the readings were 123 down to 109. All the shiny texture was gone and the hood was ready for the 2500 grit to remove the "heavy" scratching from the 1500.
Same process with the 2500 except it took around two hundred strokes before I was satisfied. The post sanding measurements were 119 down to 107.

The I hit it with the wool pad and compound, only another micron was removed. Then just for the fun of it I used a finishing foam pad and Menzerna Nano and NO change in thickness could be measured.

If all the published reports about clearcoat thickness have been accurate the with a total of 9 microns being removed (from this test hood). This amount of removal is consistent with published, allowable limits for clearcoat removal of 25% of average thickness. I would advise anyone read this tutorial on paint thickness
Automotive Paint Thickness Gages
before ANY sanding projects. As has been used in many legal disclaimers "YOUR RESULTS MAY VARY".

In conclusion, this cheapo gauge is absolutely worth the money. It could help prevent you from ruining your finish. As an example, I might be willing to attempt wet sanding my repainted door, a little less comfortable trying it on my hood, but absolutely NOT on my roof. Think of it this way. Would you rather suffer with a little bit of a scratch remaining after a modest sanding and polishing job, or would you prefer to have to pay for a repaint because you absolutely HAD to get every bit of that scratch out?
 
nice write up... the one i found only reads 0-40 mil... can you pm me the link to the one ur looking at?
 
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Very thorough review, thank you very much! A lot of people were weary that the accuracy of the gauge isn't very good compared to other gauges. For example, you take one reading at is says 100 microns but you read the exact same spot again and it reads 97 or 103 (+/- 3%). But for the money it is a great way to give you an idea of your paint thickness. Do you know of anyone in your area that has a more expensive gauge which you can make a comparison with?? That'd be the ideal test -- if they both show the same results on the same spot then this is a great deal...

Do you have to recalibrate it every time you use it? Or is it a one time deal? How long do you think the batteries will last? Thanks!
 
Do you have to recalibrate it every time you use it? Or is it a one time deal? How long do you think the batteries will last? Thanks!

That was something that I should have mentioned. I found that once you calibrate it, it held cal throughout the day. I did re-calibrate it each time I took it out of the toolbox. I never checked it from one day to the next to see if the measurement would remain the same. But on the first day that I used it I went back to the same spot on my Explorer and re-took a reading and it was always the exact same measurement. I had made a small square of tape on the hood and wrote each reading on the tape after it took it. And they were all the same over the five hour test.

As to battery life wasn't worried since it uses a readily available 9volt battery. I used the gauge for at least three hundred measurements and the battery was still good. And the battery that came with the gauge is a lousy, non alkaline type. I am just going to put a new Duracell in it. I always buy mine at Costco. They sell so many that you know that they are always fresh. And cheap too.
 
nice write up... the one i found only reads 0-40 mil... can you pm me the link to the one ur looking at?

wheres my response?

I believe that is the one he was using. It measures up to 40 mils which is 1000 um (µm = um) ... the ums (microns) are the metric measurements which are much smaller than mils, which gives better results. People usually measure in ums rather than mils.

oldmodman said:
And a button to toggle between inch and metric. The inch readings are in thousands of an inch and tenths of a thousandth. The metric is in microns and if much more useful since it reads in thousandths of a millimeter, a much smaller measurement.
 
whats the link to this item because iv been trying to find a paint thickness gauge for awhile now.
 
I would love to see an accuracy comparison between this one and some of the higher priced offerings from competitors.
 
I was wondering wat range of numbers in microns would be a big warning sign and you would know not to use any swirlremover or polish?
 
I was wondering wat range of numbers in microns would be a big warning sign and you would know not to use any swirlremover or polish?
That is, as they say, a very good question LOL

... because if you are not first owner or you have had somebody else do the detailing before you started doing it yourself or customer brings you car you have never seen before nor you know what is happening in the meantime all you can do is still guess and pray as using this kind of gauge is equivalent to asking "how deep is water" before diving head first and getting answer "xyz from surface to lowest bottom point, but there are rocks too".

I am saving up for one that will give me both. It will take a while.
 
I was wondering wat range of numbers in microns would be a big warning sign and you would know not to use any swirlremover or polish?

Here is the answer that I posted to a similar question on "another" forum.

As a follow up I will try to answer some more of the questions asked.

As far as I know this meter (and most if not all of the others) are sonic in nature. Like SONAR they bounce a sound pulse off of the metal base layer through all the "soft" paint layers above it. Then it calculates the thickness from the time it measures between the time the sound pulse is emitted and the time it gets it back. The measurement can be affected by temperature, air pressure, etc. that is why the meter should be calibrated with it's known thickness test strip before each days use.

There is no way for it to determine how thick the primer, color base coat, and the final top clearcoat are. The reason for using the meter is to let you know if the paint has been sanded before, or is it the original finish or a repaint etc.

As I posted in my original thread above, I measured the finish before and after sanding, and at each step along the way.

If you read the article that I provided a link to, it explains about the typical factory finish. That the average primer is one percentage of the total, the color base is another, and the final 25% is the top clearcoat. But you have no way of knowing if the finish has been worked on before. A good giveaway would be that the finish is absolutely perfect (showing that it may have been sanded before). So if a customer brought you a car that had perfect paint except for one key scratch you shoud be wary of sanding again. But if the same car was brought to you with tons of orangepeel you could assume that the paint is still at original factory applied thickness and it would be safe to sand out the key scratch.

But every car, case, and finish must be examined as a new case. Don't make any assumptions based on the job before it.
 
ill never wet sand...the most agressive might b like meguiars #4...other then that almost all of my paint correction is swirlremover/polish.
 
Actually there are gauges that measure all 3 or measure primer+base and then just cc.

Could you let me know who the Mfg. is and the model number?

I would like to try and research their methodology. Maybe they are using multiple transducers at different frequencies to be able to differentiate the layering.

They must be a very expensive meter. >$600.00

Sure wish that I could justify buying one that could do that. But I'm just a hobbyist detailer.
 
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